CHANGES IN ANTERIOR SEGMENT PARAMETERS...

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CHANGES IN ANTERIOR SEGMENT PARAMETERS

AND

AMPLITUDE OF ACCOMMODATION FOLLOWING

CATARACT SURGERY

DISSERTATION SUBMITTED TOWARDS PARTIAL FULFILMENT

OF THE RULES AND REGULATIONS FOR

THE M.S. (BRANCH III) OPHTHALMOLOGY EXAMINATION OF

THE TAMIL NADU DR. M.G.R. MEDICAL UNIVERSITY

TO BE HELD IN APRIL, 2017

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CHANGES IN ANTERIOR SEGMENT PARAMETERS

AND

AMPLITUDE OF ACCOMMODATION FOLLOWING

CATARACT SURGERY

SUBMITTED BY

DR. GAURAB MAJUMDAR

CHRISTIAN MEDICAL COLLEGE

VELLORE

DISSERTATION SUBMITTED TOWARDS PARTIAL FULFILMENT

OF THE RULES AND REGULATIONS FOR

THE M.S. (BRANCH III) OPHTHALMOLOGY EXAMINATION OF

THE TAMIL NADU DR. M.G.R. MEDICAL UNIVERSITY

TO BE HELD IN APRIL, 2017

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BONA FIDE CERTIFICATE

This is to certify that this dissertation entitled “Changes in Anterior Segment

Parameters and Amplitude of Accommodation following Cataract Surgery”

done towards partial fulfilment of the university regulations of the Tamil Nadu

Dr. MGR Medical University, Chennai for the award of MS (Branch III)

Ophthalmology degree examination to be conducted in April 2017, is the bona

fide original work of Dr. Gaurab Majumdar, Post Graduate student in

Ophthalmology, Christian Medical College, Vellore.

Dr. Andrew Braganza, MS, Dr. Anna B. Pulimood

Professor and Head of the Department, Principal,

Department of Ophthalmology, Department of Pathology,

Christian Medical College, Christian Medical College,

Vellore – 632001 Vellore – 632004

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done towards partial fulfilment of the university regulations of the Tamil Nadu

Dr. MGR Medical University, Chennai for the award of MS (Branch III)




Dr. Thomas Kuriakose,

MBBS, DO, DNB, FRCSEd

Professor, Department of Ophthalmology,

Christian Medical College,

Vellore – 632001.

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done towards partial fulfilment of university regulations of the Tamil Nadu Dr.

MGR Medical University, Chennai for the award of MS (Branch III)




I, the undersigned, hereby declare that I have not submitted this dissertation in

any part or full to any other university or towards any other degree.

Dr. Gaurab Majumdar,

Post Graduate Student,

Department of Ophthalmology,

Christian Medical College,

Vellore – 632001.

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ANTI-PLAGIARISM CERTIFICATE

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ANTI-PLAGIARISM CERTIFICATE

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ACKNOWLEDGEMENT

At the outset, I would like to thank God Almighty for His abundant grace

and mercy, for nothing is possible without Him.

Next, I express my sincere and heartfelt gratitude to my respected guide,

Dr. Thomas Kuriakose, Professor, Department of Ophthalmology, Christian

Medical College, Vellore, for his unending dynamic support, help and guidance

throughout the entire study. Without his youthful exuberance, it would never

have been possible on my part to complete the entire dissertation on time.

I would sincerely like to thank my co-investigators, optometrists – Mrs.

Nithya and Mr. Dinesh Kumar, for meticulously collecting the raw data for my

dissertation in spite of their hectic schedule in the OPD. A special word of thanks

to Mr. Bilto and Mr. Susikaran for sincerely and ungrudgingly helping me in my

dissertation whenever I requested them to. I can never forget the services of Mr.

Julius (retired optometrist), my respected senior and dear friend, and Mr. Albert

(MRD) who willingly called the patients and painstakingly convinced them to

complete the study whenever they failed to attend for follow up. I would also like

to take this opportunity to thank Mr. Deenadayalan, Librarian in charge of Schell,

who personally took the pains of writing down the information sheet and consent

in Tamil, in spite of his multiple commitments. I would also like to thank my co-

guide, Dr. Jayanthi Peter, for her encouragement towards timely completion of

my dissertation.

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I would like to express my sincere gratitude towards my biostatistician,

Mrs. Mahasampath Gowri, who helped me in the statistical analysis and catered

to my innumerable demands in spite of time constraints. Without her efforts, I

would have never managed to complete my dissertation on time.

I shall be forever grateful to my dear friend, Dr. Saibal Das, PG registrar,

Department of Pharmacology, for explaining in details the nitty-gritties of the

statistical analysis and helping me prepare the various graphs and tables which I

have incorporated in my dissertation. Thank you dear friend for your sincere co-

operation and unending moral support.

I would like to specially express my gratitude to Dr. Dhipak Arthur, my

dear friend and colleague, for his active co-operation and support whenever I

approached him for advice. I am also grateful to Dr. Rutika and Dr. Jophy for

their encouragement for timely submission of my dissertation. I am grateful to all

the consultants in my department for contributing cases towards the study. I

would also like to thank all the participants of the study for their patient

cooperation.

I would like to gratefully acknowledge the Institutional Review Board,

Christian Medical College, Vellore for giving approval to the project and

sanctioning the fluid research grant, without which the work would not have been

completed.

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I would like to sincerely thank my parents without whose constant

affection, blessings and moral guidance I would never have managed to complete

this dissertation on time. Last but not the least, it was my wife, who provided me

with all the necessary motivation and moral strength and took care of my health,

and ensured that I remained positive till the very end, which enabled me to

complete my dissertation.

I earnestly thank all those, not mentioned here by name, who were

instrumental in the completion of my dissertation. Thank you all very much !!!

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ABBREVIATIONS

AA Amplitude of accommodation

AAA Amplitude of apparent accommodation

ACD Anterior chamber depth

ACV Anterior chamber volume

ACA Anterior chamber angle

AL Axial length

AOD Angle-opening distance

ASOCT Anterior segment Optical Coherence Tomography BCDVA Best corrected distance visual acuity

BCNVA Best corrected near visual acuity

CCT Central corneal thickness

CCV Central corneal volume

ECCE Extracapsular cataract extraction

ICA Iridocorneal angle

ICCE Intracapsular cataract extraction

ICL Implantable contact lens

IOL Intraocular lens implantation

IOP Intraocular pressure

MSICS Manual Small Incision Cataract Surgery

NPA Near point of accommodation

PD Pupil diameter

PCIOL Posterior chamber intraocular lens implantation

Phaco Phacoemulsification

RAF Royal air force

TIA Trabecular-iris angle,

TISA Trabecular-iris space area

UCDVA Uncorrected distance visual acuity

WTW White-to-white

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TABLE OF CONTENTS

INTRODUCTION.....................................................................................01

AIM AND OBJECTIVES.........................................................................05

REVIEW OF LITERATURE.................................................................. 06

MATERIALS AND METHODS..............................................................24

RESULTS...................................................................................................39

DISCUSSION.............................................................................................68

CONCLUSION..........................................................................................77

LIMITATIONS OF THE STUDY...........................................................78

BIBLIOGRAPHY.....................................................................................79

APPENDIX A: IRB APPROVAL FORM...............................................91

APPENDIX B: INFORMATION SHEET & CONSENT FORMS...... 95

APPENDIX C: CLINICAL RESEARCH FORM................................104

APPENDIX D: DATA SHEET.............................................................. 106

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INTRODUCTION

Cataract is considered to be the most common cause of age-related

visual decline globally, accounting for nearly 50% of preventable blindness.(1)

The overall prevalence of cataract varies from 1 – 4% of the population. Cataract

occurs earlier (in the fifth decade) in Southern Asia, and later (in the sixth or

seventh decade) in the developed countries. Absence of an effective eye health

care delivery system and relatively poor surgical care for cataract leads to a high

prevalence of cataract in the developing countries. Over the next 20 years it is

estimated that the world’s population will increase by about one third,

predominantly occurring in developing countries. During the same period, the

number of people above 65 years will more than double. Therefore, there will be

approximate doubling in the incidence of cataract, visual morbidity, and need for

cataract surgery.(2)

When these patients have cataract surgery, it improves their quality of

life and they can go back to mainstream activities of daily living. Over 90%

patients after cataract surgery have many years of life ahead of them and it is

therefore important to study the pseudophakic characteristics of these eyes to

understand the various advantages and disadvantages of pseudophakia.(3,4)

Studying all aspects of cataract surgery has thus become important to improve

the visual outcome.

There has been tremendous advancement in the field of cataract surgery

over the past two decades. Till the 1960s, intracapsular cataract extraction

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(ICCE) was widely practised in which the entire lens including the capsule was

removed by rupturing the zonules without posterior chamber intraocular lens

(PCIOL) implantation. Visual rehabilitation was done using aphakic glasses or

contact lens. This technique is no longer used because of high rate of

postoperative complications like vitreous loss, retinal detachment, astigmatism,

and cystoid macular edema. Extracapsular cataract surgery (ECCE) has replaced

ICCE, in which an opening (capsulotomy) is made in the anterior lens capsule

and the nucleus is removed and cortical matter aspirated leaving the posterior

capsule intact. This method facilitates implantation of PCIOL and is associated

with lower incidence of complications compared to ICCE. Different methods of

ECCE include: i) conventional ECCE (using sutures), ii) manual small-incision

cataract surgery (MSICS) – sutureless, with implantation of a rigid IOL, and iii)

phacoemulsification. In the latter, which is the most advanced method of cataract

surgery in current practice, the nucleus is emulsified using a machine which

provides ultrasound energy for emulsifying the nuclear pieces into smaller

fragments, and generates a vacuum for aspirating the cortex, followed by

implantation of a foldable IOL.

The visual recovery after IOL implantation has improved substantially

so that cataract surgery is fast becoming a refractive surgery and freedom from

spectacles post cataract surgery is the new concept. Small-incision minimally

invasive surgery with techniques such as clear cornea or posterior limbal tunnel

incisions combined with astigmatic keratotomy and the use of foldable IOLs

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have led to early reliable refractive results. The objective of modern cataract

surgery is not only to execute a safe and excellent surgical procedure, but also to

achieve postoperative emmetropia with increased uncorrected visual acuity for

distance and near, especially with the use of multifocal and accommodating

IOLs.(5)

The attempts to provide patients with the ability to see clearly for a

range of distances (distance, intermediate and near) without dependence on

glasses has led to the development of a whole range of multifocal IOLs and

accommodative IOLs commercially. The introduction of refractive and

diffractive multifocal IOLs are associated with a high incidence of side effects

such as increased halos and glare especially during night, reduced visual acuity

and diminished contrast sensitivity. Since the ciliary body does not lose its

contractile property over time, there is a theoretical possibility that appropriate

lens design or material can restore the accommodative ability.

Accommodation is the capacity of the eye to change the refractive

power of the lens in order to automatically focus on objects at various distances.

The difference between the dioptric power, needed to focus at near point and

focus at far point is called the amplitude of accommodation (AA). It has long

been acknowledged that some aphakic patients have good near vision while

wearing aphakic glasses with only their distance correction; this phenomenon has

been called apparent accommodation. Following cataract surgery, the IOL does

not possess any power of accommodation and thus majority of pseudophakic

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patients have difficulty in near vision and require bifocal correction for near

work. Nevertheless, after cataract surgery, an increase in depth of focus due to a

small pupil or myopic astigmatism is observed in some patients; this may result

in good distance and near visual acuity without near correction. Pseudo-

accommodation, is the potential of pseudophakic eyes to sustain a good amount

of near vision with distance correction, following cataract surgery with

monofocal PCIOL implantation.

In view of the changing types of cataract surgical techniques and the

types of IOL used with these surgeries, it is possible that the post-operative

characteristics of these pseudophakic eyes are different. Our study aims to

compare the changes in various anterior segment parameters like pupil diameter,

anterior chamber depth, central corneal thickness, axial length, intraocular

pressure and amplitude of accommodation following cataract surgery using the

two most currently popular cataract surgical techniques of phacoemulsification

and Manual small incision cataract surgery (MSICS). All the parameters studied

here have a bearing on the visual outcomes. There have been studies looking at

these parameters singly or in small groups.(6–10) The results are variable. A

larger pool of studies in this direction will give us a bigger database to make

more generalised conclusions.

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AIM AND OBJECTIVES

Aim:

To compare the changes in anterior segment parameters and amplitude of

accommodation following cataract surgery.

Objectives:

1. To compare changes in pupil diameter (undilated and dilated) before and

after cataract surgery.

2. To compare changes in anterior chamber depth before and after cataract

surgery.

3. To compare changes in central corneal thickness before and after cataract

surgery.

4. To compare changes in axial length before and after cataract surgery.

5. To compare changes in intraocular pressure before and after cataract

surgery.

6. To compare changes in the amplitude of accommodation before and after

cataract surgery.

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REVIEW OF LITERATURE

Cataract surgery is one of the oldest surgical procedures known, first

documented in the fifth century B.C.(11–14) In ancient times, cataracts were

treated with a technique called “couching,” meaning lens depression.(15)

Maharshi Sushruta, an ancient Indian surgeon, first described the procedure

around 600 BC, a procedure he termed “Sushruta Samhita, Uttar Tantra.”(16–18)

This technique could only be performed when the lens had become completely

opaque, extremely hard, and heavy to the point that the supporting zonules had

become fragile. The surgeon used a lance with sufficient force to cause the

zonules to break so that the lens would dislocate into the vitreous cavity, which

occasionally helped blind patients obtain limited vision.(19) The procedure was

extremely inefficient, often resulted in total blindness and was usually

accompanied by harsh side effects.(20–22) The procedure was introduced to

China via the Silk Road during the late West Han Dynasty (206 B.C. -

9 A.C),

and it spread throughout China during the Tang Dynasty (618 -

907 A.C) and

came to be known as “jin pi shu” in Mandarin.(23) Centuries later, the technique

was modified so that a sharp fine instrument was inserted into the eye to break

the zonules to cause the dislocation.(21,24)

The first documented modern surgical removal of a cataractous lens

happened in Paris in 1747 by the French ophthalmologist Jacques Daviel and was

essentially an extracapsular cataract surgery.(25,26) The advent of topical

anaesthesia made the procedure safer and more comfortable for the patients.

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Posterior capsular opacity was however a problem and to overcome this, the

intracapsular techniques involving removal of the entire opaque lens in one piece

using an incision that went halfway around the circumference of the cornea

evolved.(27–29) Since success of surgeries in the olden days without microscope

and IOL was not very good, surgery was only limited to mature cataracts.

Considering the fact that fine sutures did not exist at that time, patients were kept

immobilized with heavy sandbags around their head during the period of wound

healing. Consequently, the early literature reporting cataract surgery routinely

documented the mortality rate secondary to pulmonary emboli.(30–32)

There has been phenomenal improvements in cataract surgery and

visual outcomes over the past few decades. The first major advance was the

development of techniques allowing the removal of all cortical lens matter while

leaving the posterior lens capsule behind.(33) The intact posterior capsule acted

as a barrier preventing lens matter from falling into the vitreous cavity while its

removal was done. This allowed less advanced cataracts to be removed since any

residual cortical fragments could be aspirated at the time of surgery and not

retained in the vitreous, where they would induce inflammation. Since the

nucleus was the only hard thing that needed to be removed in ECCE compared to

the whole lens along with the posterior capsule in ICCE, a reduction in size of

the wound was possible.(34,35) The introduction of fine sutures considerably

increased the safety and quality of results. Sutures however caused problems due

to astigmatism, suture-related infections etc.(36)

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In spite of posterior capsular opacification, ECCE became popular

because of its ability to support posterior chamber IOLs, which was a much safer

option than anterior chamber IOLs, which could be used only after ICCE.(36–39)

Thus one can see how studies on the changes in the eye after cataract surgery

enabled cataract surgery to evolve.

The most significant change in the modern era of ophthalmology was

the introduction of cataract surgery by phacoemulsification in 1967 by Dr.

Charles Kelman.(33,40,41) In this technique, the nucleus is emulsified using a

machine which provides ultrasound energy for breaking the nucleus into smaller

fragments, and generates a vacuum for aspirating the cortex, followed by

implantation of a foldable PCIOL. This procedure facilitates removal of most

grades of cataract through a small incision. The advent of phacoemulsification

transformed the execution of cataract surgery, leading to smaller and smaller

wound construction. The smaller wounds reduced the postoperative astigmatism

substantially, and decreased per-operative complications like vitreous loss,

expulsive haemorrhage, zonular dialysis etc.(33,40,42) Today, routine wounds

are < 3 mm long, and 1 mm wounds are on the horizon.(33,43)

As newer surgical techniques progressively evolved, the advancement

in lens replacement technology was equally breathtaking. Originally, no

intraocular lens (IOL) implants were used following cataract surgery, and

patients had to rely on thick aphakic glasses for distance as well as near vision.

(29,44) These were associated with a variety of unacceptable optical aberrations.

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(45,46) IOLs evolved secondary to the innovative genius and pioneering work of

Sir Nicholas Harold Lloyd Ridley, a British ophthalmologist.(47–49) He

recognized that the penetration of smashed plastic fragments from airplane

windshields into the eyes of World War II fighter pilots when their planes had

been hit, did not lead to cataract formation. On 8 February 1950, Harold Ridley

successfully implanted the first IOL at St. Thomas’ Hospital in London. He

created the first artificial IOL, leading to the creation of an entire industry.

(50–52)

The advancement of smaller surgical incisions was complemented by

the development of newer IOL implants manufactured of different foldable

materials (acrylic and silicone) in order to allow the IOLs to be inserted through a

small wound. At present, foldable IOLs available in the market can be inserted

through incisions slightly greater than 2mm.(33,43)

The foremost objective for IOL companies in recent times has been to

manufacture such an IOL design that will restore quality distance and near

vision, thereby avoiding the need for glasses.(33,53–55) The earlier endeavours

required designing of multifocal IOLs having concentric apodized diffractive

rings of varying optical strengths so that light from different distances is focused

on the retina.(56–58) These intricate IOLs are associated with optical aberrations

that are poorly tolerated. Different types of newer IOL technologies are being

manufactured that utilize moving monofocal lenses that attempt to restore natural

accommodation by restraining the shift in lens location when the ciliary muscles

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contract.(5,33) Accommodating IOLs are now available commercially, but these

lenses produce only a narrow range of accommodation, so that most patients still

rely on reading glasses for prolonged reading or seeing fine print after cataract

surgery.(53,59,60)

Finally, newer IOL implants are now available that can correct not only

myopia or hyperopia but also a variable degree of astigmatism.(61) These toric

IOLs come with a variety of astigmatic powers. When these are implanted, the

surgeon simply aligns the surface markings of the new lens with the previously

measured steep axis of the patient's astigmatism to neutralize it.

A study done by Ellwein et al. to estimate the outcomes of cataract

surgery in rural northwest India (Rajasthan) concluded that cataract surgery

patients in rural areas of India without sufficiently equipped facilities and

competent ophthalmologists, and scarcity of IOLs, are not fulfilling the full sight-

restoring scope of modern-day cataract surgery.(62) Not only the volume of

cataract surgery has to increase, but equally important is the need to stress on the

quality of cataract surgery results. Dandona et al. performed a study to evaluate

the results of cataract surgery in an urban southern Indian population. They

concluded that the very high rate of very poor and poor visual outcome, primarily

as a result of surgery-related causes and inadequate spectacle correction, suggests

that greater consideration needs to be given to improve the visual outcome of

cataract surgery.(63,64) In order to deal with cataract-related visual decline in

India, equal emphasis has to be given on quality of cataract surgery, spectacle

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correction, and follow-up care as also on the number of surgeries. Prajna et al.

evaluated the safety and efficacy of ECCE with PCIOL compared to ICCE with

aphakic glasses and concluded that the former is superior in terms of recovery of

visual acuity as well as safety.(65) Fletcher et al. compared the effects of ECCE

with PCIOL versus ICCE with aphakic glasses on daily visual function and

quality of life. They concluded that both the two modalities of cataract surgery

were associated with considerable benefits in improved everyday visual function

and vision-related quality of life.(66) Patients receiving the former noted greater

benefits and fewer visual problems than the latter. Thus, moving from aphakia to

pseudophakia has improved outcomes of cataract surgery further.

Various studies in the past have reported that the shape of the pupil and

the pupillary response are often affected following cataract surgery.(67,68) A

fixed dilated pupil may occur sometimes after ICCE and ECCE.(69–73) A study

was done by Koch et al. to determine whether pre-operative pupil size is useful in

predicting the post-operative pupil size of patients having phacoemulsification

with PCIOL implantation. They concluded that it is not possible to consistently

predict the post-operative pupil size from the pre-operative size.(6) Previous

studies have shown that the pupil usually constricts after cataract surgery,(74)

possibly as a result of release of miotic neuropeptides following surgical

trauma.(75,76) A study was done by Hayashi et al. to assess the alterations in

pupil size before and after phacoemulsification in non-diabetics and diabetics.

(77) They concluded that pupil size diminished immediately following

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phacoemulsification, but regained almost pre-operative values by 1 month after

surgery both in non-diabetics and diabetics. A strong association was found

between pre and post-operative pupil size. The pupil size in diabetics was found

to be significantly lesser than in non-diabetics after cataract surgery. Previous

studies have documented that pupil size post cataract surgery cannot be presumed

from the pre-operative size consistently, as the pupil is considerably traumatized

due to the surgery.(67,68) However, advanced phacoemulsification procedures

can preserve the comparative pre-operative pupil size. It has been widely

regarded that pupil size in diabetics is smaller than that in healthy individuals.

(78) Studies in the past have reported that the smaller pupil in diabetics may

probably be due to diabetic neuropathy of the sympathetic nerve supply of the

dilator pupillae muscle as well as local damage to muscle tissue.(79,80) Zaczek

and Zetterstrom have reported that intraoperative miosis during cataract surgery

is more marked in diabetics than in healthy subjects,(81) probably because of

more abundant miotic neuropeptides like substance P in the iris tissue of diabetic

patients.(82)

A study was done by Keuch et al. to compare the different aspects of pupil

constriction before and after implantation of an implantable contact lens (ICL).

(83) They inferred that the latency and duration of pupil constriction were

significantly increased after ICL implantation. The rate of pupil constriction and

redilatation, the pupil diameter, and the amplitude of pupillary constriction

decreased after ICL implantation. The pupil reacted slowly following insertion of

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a phakic posterior chamber ICL. The post-operative pupil diameter was lesser,

and the amplitude of constriction diminished. The changes have not proved to be

clinically significant to date. A study done by Twa et al. concluded that pupil size

measured by digital photography was more repeatable and precise than

estimation by common clinical techniques (ruler, semicircular templates, and the

Colvard pupillometer) over a wide range of illumination.(84) Digital

photography is comparatively cheaper, allows longstanding documentation, and

permits independent grading suitable for clinical research purposes.

Cataract surgery is not without problems. Complications like difficulty

in examining posterior segment following cataract surgery is commonly due to

reduction in pupil diameter.

Koranyi et al. compared anterior chamber depth (ACD) measurement

pre and post cataract surgery by phacoemulsification by A-scan versus optical

methods (Scheimpflug imaging, Orbscan and optical pachymetry).(85) Pre-

operatively, the mean A-scan values were found to be significantly less compared

to the Scheimpflug values. At 6 weeks post-operatively, the difference was more

marked. At 36 weeks, the A-scan and Scheimpflug findings remained similar.

The outcome of the Scheimpflug values were corroborated with optical

pachymetry and Orbscan analysis. The study concluded that there was reasonably

good similarity between results achieved with the three techniques on the basis of

optical principles. A study was carried out by Uçakhan et al. to evaluate changes

in ACD, anterior chamber volume (ACV), and anterior chamber angle (ACA)

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estimation by the Pentacam rotating Scheimpflug camera after uncomplicated

phacoemulsification in eyes with normal IOP and open iridocorneal

angles.(86,87) They concluded that the ACV and ACD increases and the ACA

widens in all quadrants 3 months after uneventful phacoemulsification and IOL

implantation. These changes are associated with a significant fall in IOP in the

short term. A study done by Shin et al. showed that phacoemulsification led to

significant increase in ACD and lowering of IOP in eyes with occludable angles

compared to eyes with normal open angles, suggesting that it is a treatment

option for preventing acute angle-closure attacks in eyes with occludable angles

and cataract.(7) A study was done by Altan et al. to examine the effect of

uncomplicated phacoemulsification on preoperative ACD, width of iridocorneal

angle (ICA), and IOP in normotensive eyes with open angles.(88) They

concluded that uneventful phacoemulsification resulted in decreased IOP,

increased ACD, and widening of ICA. The changes were statistically significant

over 6 months. A study was undertaken by Tai et al. to estimate angle changes

following uneventful phacoemulsification using Fourier-domain anterior segment

optical coherence tomography (ASOCT).(89) They established that

postoperatively the trabecular-iris angle (TIA), angle-opening distance (AOD),

and trabecular-iris space area (TISA) at 500mm increased significantly,

particularly in the temporal quadrant. A similar study done by Kim et al. to

quantify the changes in ACD and angle width produced by phacoemulsification

and IOL implantation in normal eyes using ASOCT, concluded that following

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uneventful phacoemulsification, the ACD and angle width significantly

increased.(90) ASOCT is a reliable method for procuring quantitative data

regarding configuration of the anterior chamber.(89–92)

Phacoemulsification with PCIOL implantation lowers IOP over the long

term in glaucomatous as well as in non-glaucomatous eyes with open angles on

gonioscopy.(8,88,93,94) Accurate prediction of change in IOP post cataract

surgery is important for the proper selection of cataract surgery, incisional

glaucoma surgery, or a combined procedure.(7) Pre-operative IOP is the only

established predictor of post-operative IOP and IOP response; the higher the pre-

operative IOP, the more it decreases after cataract surgery.(88,94,95) Issa et al.

found that the fall in IOP after cataract surgery was found to be directly

proportional to the pre-operative IOP, and inversely related to pre-operative

ACD, and a smaller pre-operative ACD was associated with a greater IOP

decrease following surgery.(95) With acute angle closure, lensectomy widens the

angle by allowing the iris to rotate posteriorly.(88) Thus, cataract surgery may be

beneficial in patients with angle closure glaucoma caused by intumescent lens.

Shin et al. found that patients with occludable angles had a larger fall in IOP after

cataract surgery.(7) On the other hand, Altan et al. found that the decrease in IOP

was not correlated with the changes in ICA width or ACD.(88) Zhou et al. found

that the preoperative ACA width on OCT did not predict the IOP-lowering effect

of cataract surgery.(96)

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As the cornea is the major refractive surface of the eye, corneal edema

following cataract surgery is likely to affect the optical properties of the eye.

Corneal edema has been known to affect IOP measurements. Endothelial cells

which could be damaged during cataract surgery are fundamental to maintaining

corneal transparency and the state of dehydration in the cornea. Specular

microscopic examination of corneal endothelial cells allows evaluation of the

size, shape, and raw quantity of endothelial cells only, whereas estimation of the

corneal thickness provides assessment of their qualitative function. Damage to

endothelial cells leads to an increase in corneal volume. According to literature,

CCT increases after clear corneal phacoemulsification.(9,97,98) Herr et al.

published a study of tonometry one day post cataract surgery estimated by two

different instruments to evaluate the possible effects of corneal edema on IOP

measurements.(99) They found large differences between the tonometry values in

the setting of post-operative corneal edema. A study was done by Ravalico et al.

to examine the morphology and function of the corneal endothelium in the early

postoperative period after ECCE and phacoemulsification.(98) They concluded

that functional endothelial failure occurred early following ECCE. Following

phacoemulsification, there was found to be minimal postoperative functional

damage to the endothelium. A study done by Lundberg et al. concluded that

postoperative corneal swelling correlates strongly to corneal endothelial cell loss

after phacoemulsification.(100) A useful way to evaluate the effects on the

corneal endothelium by phacoemulsification is to measure the difference in

17 | P a g e

pachymetry preoperatively and at day 1 postoperatively. A study was undertaken

by Wong et al. to evaluate corneal edema following phacoemulsification using

CCT and central corneal volume (CCV) derived from Scheimpflug imaging,

OCT, and ultrasound (US) pachymetry and to correlate CCV with

phacoemulsification parameters.(101–103) They concluded that non-contact

pachymetry methods (Scheimpflug imaging and ASOCT) tended to

underestimate CCT compared with US pachymetry in abnormal conditions, such

as eyes with corneal edema after cataract surgery. The change in CCV

postoperatively correlated with an increased cumulative dissipative energy,

estimated fluid used, and duration of phacoemulsification. The duration of

balanced salt solution irrigation in the anterior chamber can significantly affect

corneal volume and edema. This is particularly important to consider for resident

surgeons and other less experienced surgeons. A study by Takaćs et al. to

compare the effect of conventional phacoemulsification versus femtosecond

laser-assisted cataract surgery on corneal endothelium using Scheimpflug

imaging and non-contact specular microscopy, concluded that CCT was

significantly higher in the phaco group than in the femtolaser group.(104)

Compared with conventional phacoemulsification, femtosecond laser pre-

treatment for cataract surgery was associated with a significant reduction in early

postoperative corneal edema and endothelial cell loss.(105)

18 | P a g e

Accommodation is the capacity of the eye to change the refractive

power of the lens in order to automatically focus on objects at various

distances.(106) It is the ability of the human crystalline lens to change its shape

in order to bring objects that are close to the eye into sharp focus.

Accommodation is a physiological process in which the natural crystalline lens

changes its dioptric power in order to change its focus from distance to near. It is

measured in terms of the amplitude of accommodation (AA) using the unit

dioptre. The point at which accommodation is maximum is known as the near

point of accommodation (NPA), which is the nearest point at which small objects

can be seen clearly. The difference between the near point and the corrected far

point is called the range of accommodation. The difference between the dioptric

power, needed to focus at near point and that to focus at far point is termed as the

amplitude of accommodation (AA). It represents the difference between the

refracting power of the eye when fully accommodated and when it is completely

relaxed. It is the amount of accommodation exerted to move the focus from the

far point to the near point with the distant correction in place. It measures the

extent to which objects close to the eye can be focused. AA is calculated using a

near point rule such as the RAF rule. It is maximum during childhood and

decreases with advancing age.(107)

Helmholtz in the nineteenth century proposed that accommodation

occurs due to contraction of the ciliary body with the consequent relaxation of

the zonular fibres, connecting the ciliary body to the lens, thereby producing an

19 | P a g e

increase in the radius of curvature of the crystalline lens. The resultant increment

in lens curvature increases the refractive index of the lens, so that the light rays

from near objects are refracted toward each other to a greater extent and,

therefore, converge on the fovea. With ageing, there appears to be a significant

increase in stiffening of the lens, leading to weakening of the accommodative

process, leading to progressive difficulty in performing near work.(62–64) This

slow, physiological, naturally occurring, age-related, irreversible decrease in

maximal accommodative amplitude causing difficulty in near work (i.e.,

recession of the near point) is referred to as presbyopia.

Presbyopia is characterized by the difficulty in focusing objects for near

vision, in persons beyond 40 years, due to progressive loss of accommodation.

This condition occurs when the NPA has receded to the point that makes near

work difficult or impossible.(111) The definition of presbyopia is variable

because there is no standard distance for near work.(112) With the decrease in

AA, near work becomes difficult at a normal working distance, with symptoms

of asthenopia like blurring of near vision, headache, and eye strain etc. The onset

of symptoms varies with the patient’s preferred working distance, the nature of

the close work and the length of time for which it is done. Patients seek advice

for presbyopic symptoms at varying ages of life, and some of them even in their

late forties, may not wear presbyopic glasses. Presbyopia is generally first

reported clinically between 40 and 45 years of age, with its peak onset between

42 and 44 years in the Indian population, although its onset may occur any time

20 | P a g e

from 38 to 48 years of age, depending on a variety of factors.(113,114) The

effect of age on the onset and progression of presbyopic symptoms is well

documented. However, the role of refractive error in the genesis of presbyopia is

unclear.

A study done by Abraham et al. to estimate the relationship between

AA and refractive errors in the peri-presbyopic age group showed higher AA

among myopes between 35 and 44 years relative to emmetropes and

hypermetropes.(67) In fact, AA was found to be maximum in myopes and least

in hypermetropes till 44 years of age, and intermediate in emmetropes. Beyond

44 years, there was no change in AA amongst the three refractive groups.

Because AA is highest in myopic individuals, they require correction for

presbyopic asthenopic symptoms much later than the rest. Possible explanations

for this could be considering the fact that perhaps myopes remove their

spectacles for near work, the under-correction suitable for them slows down

presbyopic symptoms, or they sustain their accommodation for longer

duration.(111,116,117) Convergence of AA after 44 years of age among the three

refractive groups suggests that clinically undetectable lens changes starting after

40 years may be the principal reason for decreased accommodation, supporting

the idea that the human crystalline lens and not the ciliary muscle is mainly

responsible for the decline in AA with ageing.(118)

21 | P a g e

The factors that cause presbyopia are still unclear. (106–108,111) Three

factors have traditionally been considered the primary factors contributing to this

condition :-

1) The elasticity of the lens capsule decreases from youth to old age.

2) The lens substance becomes stiffer, more plastic, and more sclerotic with

advancing age. These speculated lens changes that lead to presbyopia is

probably the precursor to cataractogenesis.

3) The lens size/volume increases progressively with age. This makes the

lens capsule function less effective.

Other factors implicated include –

decreased contraction of the ciliary muscle,

slackening of zonular fibers, loss of plasticity of the Brüch’s membrane etc.

It is well documented that in tropical areas cataracts occur in a younger

age group and stiffening of the crystalline lens occurs earlier.(114) This could

possibly explain why AA in the peri-presbyopic age group is lower in the tropics

relative to the European population.(113)

Presbyopia is treated by compensating for the reduction in AA by

giving appropriate convex lenses placed in front of the eye, depending upon the

age and the visual requirements of the subject. This brings the NPA which has

receded to the subject’s comfortable working distance.(119)

It has long been shown that some aphakic patients have good near

vision while wearing aphakic glasses with only their distance correction; this

phenomenon has been called apparent accommodation.(120–123) Following

22 | P a g e

cataract surgery, the IOL does not possess any power of accommodation and thus

pseudophakic patients have difficulty in near vision and require bifocal

correction for near work. The power of the prescribed glasses depends on the

astigmatism induced by the incision, the power of the IOL implanted and the

visual needs of the particular patient. Nevertheless, after cataract surgery, an

increase in depth of focus due to a small pupil or myopic astigmatism is observed

in some patients; this may result in good distance and near visual acuity without

correction.(10,124,125) A study done by Verzella et al. revealed that low against-

the-rule simple myopic astigmatism can often offer pseudophakic patients a

rewarding independence from glasses both for distant and near vision.(126) This

phenomenon, called pseudo-accommodation, is the potential of pseudophakic

eyes to sustain a good amount of near vision with distance correction. A study

was done by Nakazawa et al. to measure the pseudo-accommodation in 42

pseudophakic eyes (34 patients) after implantation of PCIOLs.(10) The diameter

of the pupil appeared to be the most important factor in pseudo-accommodation –

the smaller the pupil, the greater the pseudo-accommodation. Pseudo-

accommodation was inversely proportional to the pupillary diameter. No

correlation, was found, however, between pseudo-accommodation and corrected

visual acuity, refractive error, corneal astigmatism, or axial length. There was a

negative correlation between pseudo-accommodation and ACD. The authors

found a statistically significant correlation between pseudo-accommodation and

depth of field.(10,127) Various factors like astigmatism, forward movement of

23 | P a g e

IOL due to the contraction of the ciliary body etc are thought to contribute to this

phenomenon.

Ciliary body contraction, the prime mover of the accommodative process,

is not affected with age. Studies using ultrasound biomicroscopy (UBM) and

magnetic resonance imaging (MRI) have shown that despite the loss of

accommodation caused by the weakening of the ciliary muscle, the function of

the ciliary body persists over time, even in pseudophakes.(60,128,129) This

continued function of the ciliary body during presbyopia is imperative, as effort

to focus on an object by the presbyopic subject, while wearing reading glasses

for near work, leads to convergence and miosis, thereby activating the ciliary

body.(130)

Monofocal IOLs afford good outcomes in uncorrected distance vision

after cataract surgery. However, they fail to provide satisfying results in near

vision.(91) Studies have shown that following cataract surgery with implantation

of monofocal IOLs, almost 2 dioptres of pseudo-accommodation can

occur.(53,59) Accommodating IOLs that can focus on objects at different

distances by an anterior shift of the optic caused by ciliary muscle contraction

have been recently proposed.(53,59,128)

24 | P a g e

MATERIALS AND METHODS

Study design

This was a tertiary hospital-based, prospective observational study.

Study setting

This study was conducted in the Department of Ophthalmology,

Christian Medical College (CMC), Vellore (Schell campus). Christian Medical

College, Vellore is a tertiary care teaching centre in South India. The average

number of patients seen per week in the outpatient clinics of the Department of

Ophthalmology, Christian Medical College, Vellore, is 2000. The average

number of patients admitted per week in the inpatient wards of the department is

160. The majority of patients who come for cataract surgery to our department

are done as in-patients to facilitate postgraduate training.

The study was conducted from November 2015 to August 2016, after

obtaining the approval of the Institutional Review Board (IRB Ref no: 9351).

Patient selection:

Consecutive patients coming for admission for cataract surgery

fulfilling the inclusion and exclusion criteria were invited for the study. Those

who were willing and gave informed consent were recruited for the study. The

following were the inclusion and exclusion criteria.

25 | P a g e

Inclusion Criteria:

1. All patients above 50 years of age with age-related cataract admitted for

cataract surgery and IOL implantation (fulfilling the eligibility criteria)

residing within 30 Km from the Schell Eye Hospital, Department of


2. All patients coming for cataract surgery with best corrected near visual

acuity (BCNVA) better than N12.

Exclusion Criteria:

The following patients were excluded from the study ―

1) All outstation patients

2) Those with BCNVA less than N12.

3) Those with any ocular pathologies like – corneal opacity, ocular

surface abnormalities (pterygium, dry eyes, lagophthalmos),

pseudoexfoliation, glaucoma, irregular pupils, chronic uveitis,

phacodonesis, diabetic retinopathy, retinal detachment, macular

degeneration, retinitis pigmentosa and myopic degeneration.

4) Patients with higher mental function abnormalities.

5) Systemic diseases like Parkinsonism, Diabetes mellitus, chronic

kidney disease, autoimmune diseases and malignancy.

6) Patients with intra-operative complications like posterior capsular rent,

surgical aphakia, iridodialysis, or anterior chamber IOL implantation.

26 | P a g e

Informed consent and recruitment

Following admission in the ward, all patients fulfilling the pre-operative

inclusion and exclusion criteria were provided with an information sheet

describing the aim and methodology of the study. The information sheet was

available in English and Tamil. They were explained regarding the nature of the

various additional tests (apart from the routine investigations) that would be

carried out during the course of the study. Following this, an informed consent

was obtained from each participant in a language understood by him/her. After

obtaining their informed consent (Appendix B), they were recruited into the

study.

The selected patients were subjected to a comprehensive

ophthalmological examination, including slit-lamp biomicroscopy, fundus

examination and measurement of intraocular pressure (IOP) using Goldmann

applanation tonometer by the principal investigator.

Figure 1: Complete ophthalmological examination by principal investigator

27 | P a g e

Preoperatively the following tests were performed by two designated

optometrists (NV, DK):

1. Visual assessment (uncorrected/best corrected visual acuity for distance

and near), using Snellen chart.

2. Near point of accommodation (NPA) & amplitude of accommodation

(AA) ― using RAF rule.

3. Pupil diameter (PD) – undilated and dilated (30 minutes after single

instillation of eye drop Tropicamide, 0.8%) ― using AL-Scan Optical

Biometer (NIDEK CO., LTD., Gamagori, Japan).

4. Axial length (AL) ― using AL-Scan Nidek optical biometer.

5. Central corneal thickness (CCT) ― using AL-Scan Nidek optical

biometer, and

6. Anterior chamber depth (ACD) ― by ultrasound A-scan (8-10 MHz

Tomey AL 4000) measurement.

Uncorrected distance visual acuity (UCDVA) was measured by one

designated optometrist (NV) using Snellen chart at a distance of 6 metres.

Objective refraction was done using a streak retinoscope (Streak retinoscope,

Heine, Germany) and refined with subjective refraction. The best corrected

distance visual acuity (BCDVA) was documented along with the power of the

corrective lenses. Visual acuity readings from the Snellen chart were converted to

the logMAR scale from the conversion table. The uncorrected near visual acuity

(UCNVA) was recorded at a distance of 33cm using the New Times Roman chart

28 | P a g e

and the best corrected near visual acuity (BCNVA) to confirm inclusion criteria

was determined after putting suitable convex lenses in the trial frame.

Figure 2: Conversion Table for Logmar to Snellen’s equivalent

29 | P a g e

The near point of accommodation (NPA) was measured in centimetres

using the Royal air force (RAF) rule with the full distance correction in place.

(132,133) The RAF rule is 50 cm long and is marked on the top in centimetres.

The NPA was measured with the patient trying to read the letters on the lowest

line (Times Roman type N.12 line) on the RAF rule target. The target was slowly

slided forwards on the RAF rule, from 50cm to the point where the patient

complained of the letters becoming slightly blurred. Then it was slowly pushed

back till the letters could just be clearly read. This point was considered as the

NPA. The NPA was recorded in cm from the rule. If the NPA was beyond 50 cm,

suitable corrective plus lenses were used to bring the NPA to 50cm or closer. The

AA was determined as the reciprocal of NPA in metres. If corrective adds were

used to bring the NPA to 50 cm or closer, the actual amplitude of

accommodation was ascertained after deducting the power of the corrective lens

used.

Figure 3: Measurement of near point of accommodation using RAF rule

30 | P a g e

Figure 4: Recording of near point of accommodation by designated optometrist

ACD was measured by another designated optometrist (DK) by ultrasound

A-scan, using a 8-10 MHz Tomey AL 4000 transducer. The patient was asked to

look straight ahead. Using a drop of topical anaesthetic (Proparacaine, 0.5%), the

A-scan probe was held at the centre of the cornea without applying any undue

pressure on the cornea. Average of 10 readings was taken.

Figure 5: Recording of anterior chamber depth by designated optometrist

31 | P a g e

The AL-Scan Optical Biometer (Nidek Co. Ltd., Gamagori, Japan) is a

novel device that can successively measure the values necessary to calculate the

power of an IOL for cataract surgery through a non-contact optical measurement

technique.(134) It is capable of measuring 6 fundamental values for cataract

surgery in 10 seconds. These include AL, radius of curvature of the cornea

(keratometry), ACD, CCT, white-to-white distance (WTW), and PD. The rapid

measurement enhances clinical efficiency and patient comfort.

Figure 6: AL-Scan Nidek optical biometer

The AL-Scan Nidek optical biometer uses an 830 nm super luminescent

diode for AL measurement based on the principle of partial coherence

interoferometry (PCI). It uses a light-emitting diode (LED) for corneal

32 | P a g e

keratometry readings and PD assessment. The AL-Scan measures the radius of

curvature of cornea (refractive power) and the steepest and flattest meridian

directions by detecting ring image projected on the patient’s cornea with a photo-

detector and calculating the image. The Scheimpflug principle is employed by

the device to measure CCT values. The device is capable of performing IOL

power calculation using various pre-programmed formulae. The manufacturers’

state that no significant training is needed to use the AL-Scan, since the device’s

3D autotracking and autoshot features perform biometric measurements as

independently as possible of operator factors. The AL-Scan device is easy and

comfortable to use and performs rapid and reproducible measurements.

Figure 7: Measurement of pupil diameter, axial length and central corneal

thickness by Nidek optical biometry by designated optometrist

33 | P a g e

PD was measured based on a captured anterior eye segment image. The

aim is to measure the stable dark-adapted horizontal pupil diameter at a

predetermined level of low ambient illumination. To achieve room illumination

at or near 1lux, all fluorescent lights were turned off and incandescent lights

made as dim as possible. It is essential to eliminate focal light sources from the

pupil testing room while measuring the undilated PD. In order to avoid

photoreceptor bleaching, slit-lamp examination and fundoscopic evaluation were

carried out at least 30 minutes after measuring the dark-adapted pupil diameter.

The selected patients were posted for cataract surgery on the following

day. Two types of cataract surgery (manual small incision cataract surgery –

MSICS, and phacoemulsification) with IOL implantation were performed on the

patients by multiple surgeons. The choice of surgery was based on multiple

factors, which included the stage of cataract, hardness of nucleus (nuclear

sclerosis), choice of IOL – rigid/foldable, and cost affordability. Those with per-

operative complications (mentioned previously) were excluded from the study.

Postoperatively, the same set of parameters (PD – undilated/dilated,

ACD, AL, CCT, IOP and AA) were re-evaluated twice in exactly the same

manner by the same designated optometrists, once at 4-6 weeks and finally at 11-

13 weeks.

The patient details and the measurements were recorded in the clinical

research form (Appendix C) and subsequently entered in the excel sheet in the

computer.

34 | P a g e

Figure 9: Detailed diagrammatic algorithm of the study

Cataract patients presenting in Out Patient Department of

Ophthalmology (Schell campus), CMC Vellore

who meet eligibility criteria

Matching desired eligibility criteria

Informed consent and recruitment

Complete ophthalmological examination, cataract surgery and

follow up at 4-6 weeks and 11-13 weeks post-operatively

Data collection by principal investigator and co-investigators

Analysis of data using appropriate statistical methods

35 | P a g e

Sample size

The sample size was calculated based on difference in PD (mm) before cataract

surgery and 1 month following cataract surgery, based on a study by Hayashi et.

al.(77) In his study, the average difference in PD between pre-op and 1 month

post-op was 0.26 with standard deviation of 0.8

where, error (α) = 5%, power (1-β) = 80%

[ N = sample size, SD = Standard Deviation, PD = Pupil diameter ]

From this, the required sample size to detect a difference of 0.26 units between

pre-op and post-op pupil diameter was calculated as 120 with 80% power and 5%

error.

Considering a 10% reduction of sample size due to operative complications and

loss to follow up, it was decided to recruit 140 patients for our study. IRB

clearance was obtained for the same.

A power analysis was done to check whether the available samples of 81 patients

were sufficient, as the desired sample size was not achieved.

Mid-term analysis of our study population on 81 subjects showed that the

average difference in PD between pre-op and 1 month post-op was found to be

0.26 with standard deviation of 0.5. Power was calculated to be 98%. Since we

= ([Z1-α/2 + Z1-β/2]

2 x SD

2)

Mean (pre-op PD – post-op PD)2

N

36 | P a g e

were having difficulty recruiting the original sample size due to poorer BCNVA

(worse than N12) than required in our patients and presence of systemic illness

(like diabetes mellitus), we recalculated the sample size requirements and found

that 81 patients were enough to detect a significant difference. Data was collected

from 98 patients for our study.

Data entry and analysis:

The data was recorded in the clinical research form and was entered on the

computer using EpiData (Version 3.1) software. All the analysis were done using

STATA 13.1 I/C software.

Quantitative variables and statistical methods:

Two types of cataract surgery were performed on the recruited patients by

multiple surgeons ―

1. Manual small incision cataract surgery (MSICS) and

2. Phacoemulsification.

Data were summarized using mean along with standard deviation for continuous

variables, and frequency along with percentage for categorical variables.

Independent t-test was used to compare baseline characteristics for continuous

variables between the two types of cataract surgery.

Chi-square test was used to test baseline characteristics of categorical variables

between the types of cataract surgery.

37 | P a g e

Additionally, a comparative analysis was performed on the various parameters

pre-operatively, and at 1 month and 3 months post-operatively between MSICS

and phacoemulsification.

Repeated measures ANOVA was performed to look into the overall change in

variables (PD, ACD, AL, CCT, IOP, AA) over time and the variation in the type

of surgery over that time was also considered and reported.

Pearson correlation was used to check correlation between amplitude of

accommodation with other parameters like anterior chamber depth, pupil

diameter, near add etc.

Any differences in the variables showing a p value of less than 0.05 were

considered to be statistically significant.

Potential confounders/suspected effect modifiers:

The potential confounders and modifiers included systemic disorders like

diabetes mellitus, the type of surgery done, type of IOL implanted and the

operating surgeon (cataract surgery was performed by multiple surgeons). There

was a possibility that the type of surgery (MSICS versus phacoemulsification)

could affect some of the parameters being studied.

Data sources/measurement:

Data was collected using a Clinical research form (Appendix C). Data regarding

all confounding factors/suspected effect modifiers were obtained by history,

clinical examination and special investigations. Pre-operatively, all selected

38 | P a g e

patients underwent a complete ophthalmological examination by the principal

investigator.

Bias:

The various anterior segment parameters were taken by the principal investigator

and co-investigators. It was however difficult to blind the technicians completely

because a look at the eye with torchlight would easily reveal whether the patients

are pre-op or post-op.

39 | P a g e

RESULTS

Over the study period from November 2015 to August 2016, a total of 109

patients fulfilling the inclusion and exclusion criteria were invited for the study.

4 patients who met the eligibility criteria were not willing to participate in the

study and so were not included.

4 patients were subsequently excluded as they did not attend for the 1 month

post-operative follow up.

Only 3 (i.e., 3.06 %) had per-operative complications which included:

a) posterior capsular rent (PCR) – 1,

b) iridodialysis – 1, and

c) post-operative endophthalmitis – 1;

These patients were thereby excluded from the study after initial recruitment.

Out of the recruited 98 patients in our study, only 74 patients completed the 3

month post-operative follow up. The remaining 24 patients did not come for the

3 month post-operative follow up study.

Demographic characteristics

Age distribution

The age of the recruited patients ranged from 50 to 78 years.

The mean age was 64.15 (± 6.74) years.

Table 1 shows the age distribution of the patients.

40 | P a g e

Table 1: Age distribution of patients

Variable

n

Mean

SD

Min

Median

Max

Age

98

64.15

6.74

50.00

64.00

78.00

Age in years

n = sample size

SD = Standard deviation

Min = Minimum age, Max = Maximum age

Gender distribution

Our study comprised of 49 males (50 %) and 49 females (50 %), with a sex ratio

of 1:1.

Type of cataract surgery:

24 patients (24.49 %) were operated upon by manual small incision cataract

surgery (MSICS) and the remaining 74 (75.51 %) underwent cataract surgery by

Phacoemulsification.

Table 2 shows the percentage distribution of cataract surgery.

Table 2: Types of cataract surgery and gender distribution

Types of surgery

n

Percentage

Males

Females

MSICS

24

24.49

12

12

PHACO

74

75.51

37

37

Total

98

100

49

49

MSICS = Manual small incision cataract surgery,

PHACO = Phacoemulsification

n – number of patients

41 | P a g e

Out of the 98 patients subjected to cataract surgery, 54 (55.10 %) were operated

on their right eye (OD) and the remaining 44 (44.90 %) underwent surgery in

their left eye (OS).

Table 3 shows the eye-wise percentage distribution among the patients.

Table 3: Eye operated upon

Eye

n

percentage

OD

54

55.10

OS

44

44.90

Total

98

100

OD = Right eye, OS = Left eye

n – number of patients

42 | P a g e

Table 4 gives the difference in undilated pupil diameter (PD) before and after

cataract surgery in the two subgroups of MSICS and phacoemulsification, as well

as overall. There was no statistical difference between the pre and post-op

undilated PD across or between groups. The difference between the post-op

undilated PD in the MSICS and Phaco group was also not significant.

The power for this was only between 5 and 45%.

Table 4: Comparison of undilated PD pre-op, and post-operatively at

1M and 3M, between MSICS and Phaco groups and also overall

Pre-operative

Post-op (1M)

Post-op (3M)

Overall

3.92 (± 0.72)

3.98 (± 0.64)

3.94 (± 0.73)

Phaco

3.93 (± 0.70)

3.94 (± 0.63)

3.89 (± 0.71)

MSICS

3.90 (± 0.79)

4.08 (± 0.69)

4.10 (± 0.79)

PD – pupil diameter (mm)

1M – post-operative at 1 month

3M – post-operative at 3 months

MSICS – Manual small incision cataract surgery

Phaco – phacoemulsification

43 | P a g e

Table 5 gives the difference in dilated PD before and after cataract surgery in the

two subgroups of MSICS and phacoemulsification, as well as overall.

Dilated PD was found to be statistically significant post-operatively at 1month (p

= 0.000) and at 3months (p = 0.000), compared to pre-operatively overall and

also in the phaco group; whereas in the MSICS group, the difference was found

to be statistically significant (p = 0.024) only at 3months post-op compared to

pre-op.

Table 5: Comparison of dilated PD pre-op and post-op at 1M and 3M,

between MSICS and Phaco groups and also overall

Pre-operative

Post-op (1M)

Post-op (3M)

Overall

5.96 (± 0.75)

5.72 (± 0.73) α

5.64 (± 0.78) β

Phaco

5.98 (± 0.72)

5.70 (± 0.73) α

5.62 (± 0.73) β

MSICS

5.92 (± 0.85)

5.77 (± 0.76)

5.68 (± 0.95) β

PD – pupil diameter (mm)




Phaco – phacoemulsification

α - statistically significant (p < 0.05) – at 1 month post-op versus pre-op

β - statistically significant (p < 0.05) – at 3 months post-op versus pre-op

44 | P a g e

Table 6 gives the difference in anterior chamber depth (ACD) before and after


as overall.

The difference in ACD was found to be statistically significant overall at post-op

1month (p = 0.000) and at 3month (p = 0.000) compared to pre-op. There was no

statistically significant difference noted between the MSICS and phaco groups,

pre-op and post-operatively.

However the power to make out a difference in the sub-groups was only --

Table 6: Comparison of ACD pre-op and post-op at 1M and 3M,


Pre-operative

Post-op (1M)

Post-op (3M)

Overall

3.31 (± 0.38)

3.65 (± 0.45) α

3.69 (± 0.39) β

Phaco

3.33 (± 0.36)

3.69 (± 0.47)

3.72 (± 0.38)

MSICS

3.26 (± 0.43)

3.51 (± 0.36)

3.60 (± 0.42)

ACD – Anterior chamber depth (mm)




Phaco – Phacoemulsification

α ─ statistically significant (p < 0.05) – at 1 month post-op versus pre-op

β ─ statistically significant (p < 0.05) – at 3 months post-op versus pre-op

45 | P a g e

Table 7 gives the difference in axial length (AL) before and after cataract surgery

in the two subgroups of MSICS and phacoemulsification, as well as overall.

There was no statistically significant difference in AL values among the 3

subgroups, pre-operatively and at post-op 1month, and 3month. Between the

MSICS and phaco subgroups also, there was no statistically significant difference

pre-operatively and at post-operatively.

Table 7: Comparison of AL pre-op and post-op at 1M and 3M, between

MSICS and Phaco groups and also overall

Pre-operative

Post-op (1M)

Post-op (3M)

Overall

23.10 (± 0.91)

23.06 (± 0.88)

23.09 (± 0.81)

Phaco

23.23 (± 0.91)

23.18 (± 0.88)

23.17 (± 0.78)

MSICS

22.73 (± 0.82)

22.70 (± 0.79)

22.81 (± 0.87)

AL – Axial length (mm)





46 | P a g e

Table 8 gives the difference in Central corneal thickness (CCT) before and after


as overall.

There was a statistically significant difference (p = 0.000 – overall & phaco, p =

0.029 – MSICS) between the pre-operative and post-operative CCT at one month

in all the three groups. However at three months, this difference had disappeared

in all groups, compared to pre-op. There was also a statistically significant

difference (p = 0.000 – overall, p = 0.002 – phaco) in the corneal thickness

between 1month and 3 months post-operative in the phaco and overall group.

There was no statistical difference in the three month post-op values in the

MSICS group, compared to 1 month post-op. The difference in CCT at post-op

1month and at 3 months was found to be statistically significant (p = 0.000) in

the phaco group compared to the MSICS group, and also pre-operatively.

Table 8: Comparison of CCT pre-op and post-op at 1M and 3M,


Pre-operative

Post-op (1M)

Post-op (3M)

Overall

499.72 (± 33.16)

506.09 (± 34.78) α

500.18 (± 33.76) γ

Phaco

502.09 (± 32.87)

508.69 (± 35.61) α

502.39 (± 33.45) γ

MSICS

492.42 (± 33.66)

498.08 (± 31.44) α

492.76 (± 34.77)

CCT ─ Central corneal thickness (microns, μ)

α - statistically significant (p < 0.05) – at 1 month post-op versus pre-op

γ - statistically significant (p < 0.05) – at 3 months post-op versus 1 mnth post-op

47 | P a g e

Graph showing variation in CCT in the 3 groups, pre-operatively and

at post-op 1M and 3M

We looked at variations in CCT over time in the 3 groups. As evident from the

graph, our study shows that in all the 3 groups, there is an increase in CCT from

pre-op to post-operatively at 1 months, which reaches the baseline value around 3

months post-operatively.

Fig. 1: Graph showing variation in CCT in the 3 groups, pre-operatively

and at post-op 1M and 3M

CCT ─ Central corneal thickness (microns, μ)



480

485

490

495

500

505

510

Pre-operative Post-op (1M) Post-op (3M)

Overall

Phaco

SICS

48 | P a g e

Table 9 gives the difference in intraocular pressure (IOP) before and after


as overall.

The difference in IOP was found to be statistically significant at post-op 1month

(p = 0.000) and at 3months (p = 0.000) compared to pre-op, and also at post-op

3months compared to post-op 1month (p = 0.004 – MSICS, p = 0.000 – phaco) in

all the 3 groups. The difference in IOP at post-op 1month (p = 0.000) and

3months (p = 0.012) was found to be statistically significant in the phaco group

compared to the MSICS group. Pre-operatively there was no difference between

the two.

Table 9: Comparison of IOP pre-op and post-op at 1M and 3M,


Pre-operative

Post-op (1M)

Post-op (3M)

Overall

15.07 (± 2.50)

12.99 (± 2.18) α

11.49 (± 2.04) β γ

Phaco

15.18 (± 2.62)

13.28 (± 2.27) α

11.74 (± 2.11) β γ

MSICS

14.75 (± 2.13)

12.08 (± 1.64) α

10.65 (± 1.58) β γ

IOP ─ Intraocular pressure (mm Hg)

α – statistically significant (p < 0.05) – at 1 month post-op versus pre-op

β – statistically significant (p < 0.05) – at 3 month post-op versus pre-op

γ – statistically significant (p < 0.05) – at 3 months post-op versus 1 mnth post-op

49 | P a g e

Table 10 gives the difference in uncorrected distance visual acuity (UCDVA)

before and after cataract surgery in the two subgroups of MSICS and

phacoemulsification, as well as overall.

UCDVA was found to be statistically significant at post-op 1month (p = 0.000)

and at 3months (p = 0.000), compared to pre-op in both MSICS and phaco

groups, as well as overall. Between the MSICS and phaco subgroups also, there

was no statistically significant difference in UCDVA pre-operatively and post-

operatively.

Table 10: Comparison of UCDVA pre-op and post-operatively at 1M

and 3M, between MSICS and Phaco groups and also overall

Pre-operative

Post-op (1M)

Post-op (3M)

Overall

0.77 (± 0.25)

0.35 (± 0.19) α

0.33 (± 0.19) β

Phaco

0.76 (± 0.25)

0.33 (± 0.18) α

0.31 (± 0.18) β

MSICS 0.79 (± 0.25)

0.40 (± 0.20) α

0.39 (± 0.21) β

UCDVA – Uncorrected visual acuity (LogMAR units)






50 | P a g e

Table 11 gives the difference in best corrected distance visual acuity (BCDVA)



The difference in BCDVA was found to be statistically significant at post-op

1month (p = 0.000) and at 3months (p = 0.000), compared to pre-op in both

MSICS and phaco groups, as well as overall. There was a statistically significant

difference in BCDVA pre-operatively (p = 0.005) and at 3months post-op (p =

0.004) between the MSICS and phaco groups. This difference was not

statistically significant at post-op 1month.

Table 11: Comparison of BCDVA pre-op and post-op at 1M and 3M,


Pre-operative

Post-op (1M)

Post-op (3M)

Overall

0.30 (± 0.13)

0.04 (± 0.09) α

0.04 (± 0.08) β

Phaco

0.29 (± 0.13)

0.03 (± 0.08) α

0.03 (± 0.07) β

MSICS 0.35 (± 0.13)

0.07 (± 0.10) α

0.09 (± 0.10) β

BCDVA – Best corrected visual acuity (LogMAR units)

MSICS – Manual small incision cataract surgery Phaco – Phacoemulsification



51 | P a g e

Tables 12-14 ― shows the variation in AAA (amplitude of apparent

accommodation) across the three groups, pre-operatively as well as post-

operatively at 1 month and at 3 months.

Table 12 ― AAA in overall group

AAA

n

Mean

SD

Min

Median

Max

Pre-op

98

1.64

0.59

0.50

2.04

2.94

Post-op 1M

98

1.97

0.46

0.79

2.08

3.13

Post-op 3M

74

2.02

0.42

1.00

2.08

3.13

AAA ― amplitude of apparent accommodation



n = sample size


Min = Minimum age,

Max = Maximum age

Table 13 ― AAA in MSICS group

AAA

n

Mean

SD

Min

Median

Max

Pre-op

24

1.45

0.63

0.54

1.17

2.22

Post-op 1M

24

1.93

0.56

0.79

2.08

2.63

Post-op 3M

17

2.00

0.50

1.08

2.13

2.56

52 | P a g e

Table 14 ― AAA in Phaco group

AAA

n

Mean

SD

Min

Median

Max

Pre-op

74

1.70

0.57

0.50

2.04

2.94

Post-op 1M

74

1.98

0.42

1.00

2.08

3.13

Post-op 3M

57

2.03

0.40

1.00

2.08

3.13

AAA ― amplitude of apparent accommodation




n = sample size


Min = Minimum age,

Max = Maximum age

53 | P a g e

Table 15 gives the difference in amplitude of apparent accommodation (AAA)



In all the 3 groups, the increase in AAA was found to be statistically significant

at post-op 1month (p = 0.000) and at 3months (p = 0.000), compared to pre-op.

The change in AAA was found to be statistically significant (p = 0.006) pre-

operatively between MSICS and phaco groups, but not post-operatively.

Table 15: Comparison of AAA pre-op and post-operatively at 1M and

3M, between MSICS and Phaco groups and also overall

Pre-operative

Post-op (1M)

Post-op (3M)

Overall

1.64 (± 0.59)

1.97 (± 0.46) α

2.02 (± 0.42) β

Phaco

1.70 (± 0.57)

1.98 (± 0.42) α

2.03 (± 0.40) β

MSICS 1.45 (± 0.63)

1.93 (± 0.56) α

2.00 (± 0.50) β

AAA – Amplitude of apparent accommodation (dioptres)






54 | P a g e

Table 16 gives the difference in Near add before and after cataract surgery in the

two subgroups of MSICS and phacoemulsification, as well as overall.

The decrease in Near add was found to be statistically significant at post-op

1month (p = 0.000) and at 3month (p = 0.000), compared to pre-op in both

MSICS and phaco groups, as well as overall. Between the MSICS and phaco

subgroups, there was no statistically significant difference in near add pre-

operatively and post-operatively.

Table 16: Comparison of Near Add pre-op and post-operatively at 1M

and 3M, between MSICS and Phaco groups and also overall

Pre-operative

Post-op (1M)

Post-op (3M)

Overall

2.76 (± 0.25)

2.52 (± 0.20) α

2.48 (± 0.20) β

Phaco

2.75 (± 0.26)

2.52 (± 0.21) α

2.49 (± 0.22) β

MSICS

2.76 (± 0.25)

2.52 (± 0.16) α

2.46 (± 0.13) β

Near add (dioptres)






55 | P a g e

Tables 17-19 ― gives overall bird’s eye view of the various parameters studied

individually (MSICS and phaco) in the entire study sample and in the subgroups

of MSICS and phacoemulsification.

Table 17: Overall comparison of various parameters between pre-op,

and at post-op 1M and 3M

Variables

Pre-operative

Post-op (1M)

Post-op (3M)

PD undil

3.92 (± 0.72)

3.98 (± 0.64)

3.94 (± 0.73)

PD dil

5.96 (± 0.75)

5.72 (± 0.73) α

5.64 (± 0.78) β

ACD

3.31 (± 0.38)

3.65 (± 0.45) α

3.69 (± 0.39) β

AL

23.10 (± 0.91)

23.06 (± 0.88)

23.09 (± 0.81)

CCT

499.72 (± 33.16)

506.09 (± 34.78) α

500.18 (± 33.76) γ

IOP

15.07 (± 2.50)

12.99 (± 2.18) α

1.49 (± 2.04) β γ

AAA

1.64 (± 0.59)

1.97 (± 0.46) α

2.02 (± 0.42) β

UCDVA

0.77 (± 0.25)

0.35 (± 0.19) α

0.33 (± 0.19) β

BCDVA

0.30 (± 0.13)

0.04 (± 0.09) α

0.04 (± 0.08) β

Near add 2.76 (± 0.25) 2.52 (± 0.20) α

2.48 (± 0.20) β






56 | P a g e

Table 18: Comparison of various parameters by MSICS pre-op and at

post-op 1M and 3M

Variables

Pre-operative

Post-op (1M)

Post-op (3M)

PD undil

3.90 (± 0.79)

4.08 (± 0.69)

4.10 (± 0.79)

PD dil

5.92 (± 0.85)

5.77 (± 0.76)

5.68 (± 0.95) β

ACD

3.26 (± 0.43)

3.51 (± 0.36)

3.60 (± 0.42)

AL

22.73 (± 0.82)

22.70 (± 0.79)

22.81 (± 0.87)

CCT

492.42 (± 33.66)

498.08 (± 31.44) α

492.76 (± 34.77)

IOP

14.75 (± 2.13)

12.08 (± 1.64) α

10.65 (± 1.58) β γ

AAA 1.45 (± 0.63)

1.93 (± 0.56) α

2.00 (± 0.50) β

UCDVA 0.79 (± 0.25) 0.40 (± 0.20) α

0.39 (± 0.21) β

BCDVA 0.35 (± 0.13) 0.07 (± 0.10) α

0.09 (± 0.10) β

Near add 2.76 (± 0.25) 2.52 (± 0.16) α

2.46 (± 0.13) β







57 | P a g e

Table 19: Comparison of various parameters by Phaco pre-op and at

post-op 1M and 3M

Variables

Pre-operative

Post-op (1M)

Post-op (3M)

PD undil

3.93 (± 0.70)

3.94 (± 0.63)

3.89 (± 0.71)

PD dil

5.98 (± 0.72)

5.70 (± 0.73) α

5.62 (± 0.73) β

ACD

3.33 (± 0.36)

3.69 (± 0.47)

3.72 (± 0.38)

AL

23.23 (± 0.91)

23.18 (± 0.88)

23.17 (± 0.78)

CCT

502.09 (± 32.87)

508.69 (± 35.61) α

502.39 (± 33.45) γ

IOP

15.18 (± 2.62)

13.28 (± 2.27) α

11.74 (± 2.11) β γ

AAA

1.70 (± 0.57)

1.98 (± 0.42) α

2.03 (± 0.40) β

UCDVA 0.76 (± 0.25) 0.33 (± 0.18) α

0.31 (± 0.18)

β

BCDVA 0.29 (± 0.13) 0.03 (± 0.08) α

0.03 (± 0.07) β

Near add 2.75 (± 0.26) 2.52 (± 0.21) α

2.49 (± 0.22) β







58 | P a g e

Tables 20-22 ― gives comparison between MSICS and phaco for the various

parameters, pre-operatively and post-operatively.

Table 20 ─ shows that between the MSICS and phaco groups, the difference in

the AL, CCT, AAA and BCDVA values were statistically significant (p = 0.000)

pre-operatively.

Table 20: Preop comparison ― MSICS versus Phaco:

Variables

MSICS

PHACO

PD undil

3.90 (± 0.79)

3.93 (± 0.70)

PD dil

5.92 (± 0.85)

5.98 (± 0.72)

ACD

3.26 (± 0.43)

3.33 (± 0.36)

AL

22.73 (± 0.82)

23.23 (± 0.91) ¥

CCT

492.42 (± 33.66)

502.09 (± 32.87)

¥

IOP

14.75 (± 2.13)

15.18 (± 2.62)

AAA

1.45 (± 0.63)

1.70 (± 0.57) ¥

UCDVA 0.79 (± 0.25) 0.76 (± 0.25)

BCDVA 0.35 (± 0.13) 0.29 (± 0.13)

¥

Near add 2.76 (± 0.25) 2.75 (± 0.26)



¥ – statistically significant (p < 0.05) between the two groups pre-operatively

59 | P a g e

Table 21 shows that at 1month post-op between MSICS and phaco, the

difference in the AL, CCT, and IOP values were statistically significant

(p = 0.000).

Table 21: Post-op 1 Month comparison ― MSICS versus Phaco:

Variables

MSICS

PHACO

PD undil

4.08 (± 0.69)

3.94 (± 0.63)

PD dil

5.77 (± 0.76)

5.70 (± 0.73)

ACD

3.51 (± 0.36)

3.69 (± 0.47)

AL

22.70 (± 0.79)

23.18 (± 0.88) ¢

CCT

498.08 (± 31.44)

508.69 (± 35.61) ¢

IOP

12.08 (± 1.64)

13.28 (± 2.27) ¢

AAA

1.93 (± 0.56)

1.98 (± 0.42)

UCDVA 0.40 (± 0.20) 0.33 (± 0.18)

BCDVA 0.07 (± 0.10) 0.03 (± 0.08)

Near add 2.52 (± 0.16) 2.52 (± 0.21)



¢ – statistically significant (p < 0.05) between the two groups at 1 month post-op

60 | P a g e

Table 22 shows that at 3months post-op between MSICS and phaco, the

difference in the AL (p = 0.000), CCT (p = 0.000), IOP (p = 0.012) and BCDVA

(p = 0.004) values were statistically significant.

Table 22: Post-op 3 Month comparison ― MSICS versus Phaco:

Variables

MSICS

PHACO

PD undil

4.10 (± 0.79)

3.89 (± 0.71)

PD dil

5.68 (± 0.95)

5.62 (± 0.73)

ACD

3.60 (± 0.42)

3.72 (± 0.38)

AL

22.81 (± 0.87)

23.17 (± 0.78) §

CCT

492.76 (± 34.77)

502.39 ( ±33.45) §

IOP

10.65 (± 1.58)

11.74 (± 2.11) §

AAA

2.00 (± 0.50)

2.03 (± 0.40)

UCDVA 0.39 (± 0.21) 0.31 (± 0.18)

BCDVA 0.09 (± 0.10) 0.03 (± 0.07) §

Near add 2.46 (± 0.13) 2.49 (± 0.22)



§ – statistically significant (p < 0.05) between the two groups at 3 month post-op

61 | P a g e

Correlation between AAA and PD undilated ―

We looked for correlation between AAA and undilated PD pre-operatively and at

3 months post-operatively.

Fig. 2 – Correlation between AAA and PD undil (pre-op)

The above graph shows no correlation between AAA and PD undil (pre-

operative) with a Pearson correlation coefficient of 0.0053 and p-value of 0.9589

(not statistically significant).

62 | P a g e

Correlation between AAA and PD undil (3M post-op)

Fig. 3 – Correlation between AAA and PD undil (3M post-op)

The above graph shows negative correlation between AAA and PD undilated

(3months post-op) with a Pearson correlation coefficient of - 0.1547 and p-value

of 0.1881 (not statistically significant).

Table 23: Summary of correlation between AAA and PD undilated

Pre-operative (n = 98)

Post-operative 1M (n = 98)

Post-operative 3M (n = 74)

r

p value

r

p value

r

p value

PD undil

0.0053

0.9589

- 0.1315

0.1967

- 0.155

0.1881

r – Pearson’s correlation coefficient, n = number of subjects

The above table summarizes the correlation between AAA and PD (undilated).

There is no correlation between AAA and PD (undilated) pre-operatively.

The negative correlation between AAA and PD (undilated) is not statistically

significant at post-op 1month and at 3months.

63 | P a g e

Correlation between AAA and ACD ―

We looked for correlation between AAA and ACD pre-operatively and at 3

months post-operatively.

Fig. 4 – Correlation between AAA and ACD (pre-op)

The above graph shows no correlation between AAA and ACD (pre-op) with a

Pearson correlation coefficient of 0.0156 and p value of 0.8788 (not statistically

significant).

64 | P a g e

Correlation between AAA and ACD (3M post-op) ―

Fig. 5 – Correlation between AAA and ACD (3M post-op)

The above graph shows negative correlation between AAA and ACD (3month

post-op) with a Pearson correlation coefficient of - 0.1286 and p-value of

0.2748 (not statistically significant).

Table 24: Correlation between AAA and ACD

Pre-operative

(n = 98)

Post-operative 1M

(n = 98)

Post-operative 3M

(n = 74)

r

p value

r

p value

r

p value

ACD

0.0156

0.8788

0.0122

0.9052

- 0.1286

0.2748

r – correlation coefficient, n = number of patients

The above table summarizes the correlation between AAA and ACD.

There is a negative correlation at post-op 3months, which is not statistically

significant.

65 | P a g e

Correlation between AAA and Near add ―

We looked for correlation between AAA and Near add pre-operatively and at 1

and 3 months post-operatively.

Fig. 6 – Correlation between AAA and Near add (pre-op)

The above graph shows negative correlation between AAA and Near add (pre-

op) with a Pearson correlation coefficient of - 0.1990 and p-value of 0.0495

(statistically significant).

66 | P a g e

Correlation between AAA and Near add (1M post-op) ―

Fig. 7 – Correlation between AAA and Near add (1M post-op)

The above graph shows negative correlation between AAA and Near add (1M

post-op) with a Pearson correlation coefficient of - 0.2286 and p-value of

0.0236 (statistically significant).

67 | P a g e

Correlation between AAA and Near add (3M post-op) ―

Fig. 8 – Correlation between AAA and Near add (3M post-op)

The above graph shows negative correlation between AAA and Near add

(3months post-op) with a Pearson correlation coefficient of - 0.3315 and p-value

of 0.0039 (statistically significant).

Table 25: Correlation between AAA and Near add

Pre-operative

(n = 98)

Post-operative 1M

(n = 98)

Post-operative 3M

(n = 74)

r

p value

r

p value

r

p value

ACD

- 0.1990

0.049 *

- 0.2286

0.0236 *

- 0.3315

0.003 *

r – correlation coefficient, * p < 0.05 (statistically significant)

The above table summarizes the correlation between AAA and near add.

There is a negative correlation, which is statistically significant at pre-op and at

post-op 1month and at 3months.

68 | P a g e

DISCUSSION

Cataract surgery is an evolving surgery and this continuous evolution

has occurred only through constant search and research of both the procedures

involved and their outcomes. So much has been the refinement over the past, that

it has moved from a sight-restoring surgery to a vision-enhancing surgery or

refractive surgery.

This study was specially designed with the idea of studying the

apparent amplitude of accommodation (AAA) in patients before and after

cataract surgery. This can be difficult as patients with cataract have so much

decrease in near vision that near vision assessment is not possible before surgery.

With improvement of cataract surgery outcomes however, now patients are

operated much earlier than before. So we decided to recruit patients with near

vision better than N12, so that NPA can be recorded on the RAF rule with letter

sizes not very different from the normal near N6 letter size. The problem with

this, however, was that the number of patients we could recruit was lower than

we anticipated. We had to redo a sample size calculation based on our own

patients studied. Since there was a bias towards doing phacoemulsification for

the more immature cataracts, our sample was biased towards having more

patients undergoing phaco rather than MSICS. Though there are more

sophisticated methods of assessing AAA like aberrometry and Scheimpflug

camera, we had no access to those in our institution and hence we used a

functional measure of AAA using NPA.

69 | P a g e

We had to make an alteration in our study methodology with respect to

ACD calculation when we realised that the Nidek optical biometer was not

capable of measuring ACD in pseudophakic patients. We therefore had to switch

to the ultrasound mode only for measuring ACD both pre-op as well as post-op.

Various studies in the past have reported that the shape of the pupil and

the pupillary response are often affected following cataract surgery.(67,68) A

study was done by Koch et al. to determine whether preoperative pupil size is

useful in predicting the postoperative pupil size of patients having

phacoemulsification with PCIOL implantation.(6) They concluded that it is not

possible to consistently predict the post-operative pupil size from the pre-

operative size. Previous studies have shown that the pupil usually constricts after

cataract surgery,(74) possibly as a result of release of miotic neuropeptides

following surgical trauma.(75,76) Previous studies by Koch et al, Gibbens et al.

and Yap et al. have documented that pupil size post cataract surgery cannot be

presumed from the preoperative size consistently, as the pupil is considerably

traumatized due to the surgery.(67,68) However, advanced phacoemulsification

procedures can preserve the comparative pre-operative pupil size. It has been

widely regarded that pupil size in diabetics is smaller than that in healthy

individuals.(78) Studies in the past have reported that the smaller pupil in

diabetics may probably be due to diabetic neuropathy of the sympathetic nerve

supply of the dilator pupillae muscle as well as local damage to muscle tissue.

(79,80) Zaczek and Zetterstrom have reported that intraoperative miosis during

70 | P a g e

cataract surgery is more marked in diabetics than in healthy subjects,(81)

probably because of more abundant miotic neuropeptides like substance P in the

iris tissue of diabetic patients.(82) For these reasons we did not include diabetic

patients in our study, so that diabetes and its effects do not affect our study.

A study was done by Keuch et al. to compare the different aspects of

pupil constriction before and after implantation of an implantable contact lens

(ICL).(83) They inferred that the latency and duration of pupil constriction were

significantly increased after ICL implantation. The rate of pupil constriction and

redilation, the pupil diameter, and the amplitude of pupillary constriction

decreased after ICL implantation. The postoperative pupil diameter was lesser,

and the amplitude of constriction diminished. The changes have not proved to be

clinically significant to date. A study done by Twa et al. concluded that pupil size

measured by digital photography was more repeatable and precise than

estimation by common clinical techniques (ruler, semicircular templates, and the

Colvard pupillometer) over a wide range of illumination.(84). In our study, the

Nidek optical biometer used digital photography technique to assess the PD.

A study was done by Hayashi et al. to assess the alterations in pupil size

before and after phacoemulsification in non-diabetics and diabetics.(77) They

concluded that pupil size diminished immediately following phacoemulsification,

but regained almost pre-operative values by 1 month after surgery both in non-

diabetics and diabetics. At one month post operative period, they found that the

undilated PD was significantly less than pre-operative PD. In our study, we

71 | P a g e

looked for both the dilated and undilated PD pre and post-operatively. There are

not many studies that have looked at the dilated PD difference post cataract

surgery. Our study, unlike Hayashi et al. found that, there was no difference

between the pre and 1month post-operative undilated PD. The reason for this we

presume may be the fact that, post-operatively many of our patients continue to

use the cycloplegics for much longer than the stipulated one week, because they

do not like to throw off the remaining cycloplegic available in the bottle. The

dilated PD, however, was smaller post-operatively in our study both at one and

three months post-operatively and it stands to reason that post-op inflammation

and fibrosis increases the rigidity of the iris and prevents dilatation. It is also

interesting to note that at three months post-op, the dilatation further decreases

compared to one month. Here again it is well know that scarring of tissues

continues for up to 6 months post injury and is the likely reason for further

decrease in PD at 3 months. Clinically too, one observes that pseudophakic

patients do not dilate as well as normal patients. Complications like difficulty in

examining posterior segment following cataract surgery is commonly due to

reduction in pupil diameter.

Another interesting finding in our study was the larger post-op

undilated PD in patients with MSICS compared to phacoemulsification. However

this was not statistically significant. This small difference is probably due to the

micro-ruptures that occur in the sphincter muscles of the iris due to nucleus

72 | P a g e

delivery in MSICS. To the best of our knowledge there is no study comparing

pupil diameter between phacoemulsification and MSICS.

A study was done by Nemeth et al to compare ACD measurements in

phakic and pseudophakic eyes by Pentacam versus ultrasound device.(135) They

found that in the phakic group, the mean ACD was 2.87 ± 0.4 mm with the

Pentacam and 2.89 ± 0.49 mm with ultrasound A-scan (US) (p = 0.84). In the

pseudophakic group, the mean ACD was 3.41 ± 0.28 mm and 3.97 ± 0.45 mm,

respectively (p < 0.001). There was a correlation between measurements taken by

both the instruments. They also found a difference between the pre and post-op

ACD in these patients. In our study too, we found ACD more post-operatively

when the whole group was studied together. This was however not seen when

MSICS or phaco was taken individually as a group. This raises the issue of the

presence of a confounder.

Phacoemulsification with PCIOL implantation lowers IOP over the long

term in glaucomatous as well as in non-glaucomatous eyes with open angles on

gonioscopy. Issa et al. found that the fall in IOP after cataract surgery was found

to be directly proportional to the preoperative IOP, and inversely related to

preoperative ACD, and a smaller preoperative ACD was associated with a greater

IOP decrease following surgery.(95) With acute angle closure, lensectomy

widens the angle by allowing the iris to rotate posteriorly.(88) Thus, cataract

surgery may be beneficial in patients with angle closure glaucoma caused by

intumescent lens. Shin et al. found that patients with occludable angles had a

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larger fall in IOP after cataract surgery.(7) On the other hand, Altan et al. found

that the decrease in IOP was not correlated with the changes in ICA width or

ACD.(88) In our study, we too found a significant IOP lowering effect of cataract

surgery. In addition we also found that MSICS lowers IOP more than

phacoemulsification. The possible explanations for this lower IOP post-

operatively are, unrecognised wound leaks from the larger scleral incision or the

MSICS surgery itself with the nuclear rotation in the anterior chamber causing

some changes in the iris root like small irido-dialysis clefts causing further

reduction in the IOP. Pre-operatively there was no difference between the IOP of

the phacoemulsification and MSICS group.

Specular microscopic examination of corneal endothelial cells allows

evaluation of the size, shape, and raw quantity of endothelial cells only, whereas

estimation of the corneal thickness provides assessment of their qualitative

function. Damage to endothelial cells leads to an increase in corneal volume.

According to literature, CCT increases after clear corneal phacoemulsification.

(9,98) A study done by Lundberg et al. concluded that postoperative corneal

swelling correlates strongly to corneal endothelial cell loss after

phacoemulsification.(100) A useful way to evaluate the effects on the corneal

endothelium by phacoemulsification is to measure the difference in pachymetry

pre-operatively and at day 1 post-operatively. In our study, we found that there

was a significant difference between the pre-operative and post-operative CCT at

one month in all the three groups. However at three months, this difference had

74 | P a g e

disappeared in all groups, compared to pre-op. There was also a significant

difference in CCT between 1month and 3 months post-operative in the phaco and

overall group. The fact that the corneal oedema does not resolve completely by

one month raises the question of giving glasses at one month since there is bound

to be corneal curvature differences with resolution of corneal edema.

It has long been shown that some aphakic patients have good near

vision while wearing aphakic glasses with only their distance correction; this

phenomenon has been called apparent accommodation.(120–123) Following

cataract surgery, the IOL does not possess any power of accommodation and thus

pseudophakic patients have difficulty in near vision and require bifocal

correction for near work. The power of the prescribed glasses depends on the

astigmatism induced by the incision, the power of the IOL implanted and the

visual needs of the particular patient. After cataract surgery, an increase in depth

of focus due to a small pupil or myopic astigmatism is observed in some patients;

this may result in good distance and near visual acuity without correction

(10,124,125,136) A study done by Verzella et al. revealed that low against-the-

rule simple myopic astigmatism can often offer pseudophakic patients a

rewarding independence from glasses both for distant and near vision.(126) This

phenomenon, called pseudo-accommodation, is the potential of pseudophakic

eyes to sustain a good amount of near vision with distance correction. A study

was done by Nakazawa et al. to measure the pseudo-accommodation in 42

pseudophakic eyes (34 patients) after implantation of PCIOLs. The diameter of

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the pupil appeared to be the most important factor in pseudo-accommodation ―

the smaller the pupil, the greater the pseudo-accommodation. There was a

negative correlation between pseudo-accommodation and ACD. The authors

found a statistically significant correlation between pseudo-accommodation and

depth of field.(10,127,136) Various factors like astigmatism, forward movement

of IOL due to the contraction of the ciliary body etc are thought to contribute to

this phenomenon.

We wanted to evaluate if this pseudo or apparent amplitude of

accommodation was related to the cataract surgery and IOL implantation or

related to the factors in the eye independant of this. It is for this reason we chose

patients with good corrected near vision pre-operatively so that one could

compare with the good corrected post op near acuity. In our study, we found that

there was an increase in AAA in patients after cataract surgery both in the whole

group and sub-groups for MSICS and phacoemulsification. The AAA was found

to be significantly higher in the phaco group pre-operatively compared to MSICS

but this difference was not seen post operatively. The increase in AAA

postoperatively seen in conjunction with the disappearance of AAA difference in

the two sub-groups disappearing post-operatively suggests that the cataract

surgery-related changes itself and to a greater extent some ocular factors

contribute to the AAA. The cataract surgery-related changes could be better

media clarity, corneal astigmatic changes, pupil diameter and ACD changes.

There seems to be a lot of scope to study the ocular factors contributing to AAA.

76 | P a g e

Though other authors found a relation between AAA and factors like

ACD and PD, we found very little correlation. It was also surprising that we

found only a small negative correlation between AAA and the near add

prescribed and this raises a lot of questions about what is being measured.

Accommodation and AAA is still an enigma and there is a lot of scope

to explore its physiology to get better insights into near vision mechanisms so as

to conquer a universal ageing phenomenon.

77 | P a g e

CONCLUSIONS

1) There was no statistically significant difference between the pre and post-op

undilated pupil diameters after cataract surgery. However dilated pupil diameter

was found to be significantly less post-operatively compared to the pre-operative

measurements.

2) The anterior chamber depth was found to be significantly deeper after cataract

surgery and IOL implantation.

3) Corneal thickness increases after cataract surgery and remains significantly

thicker than the pre-operative value at one month after surgery. The corneal

thickness however comes back to baseline values after 3 months.

4) Axial length remains unchanged after cataract surgeries.

5) Post-operative intraocular pressure was found to be significantly lower than

pre-operative values in patients having cataract surgery and IOL implantation.

6) Apparent amplitude of accommodation increased after cataract surgery and

IOL implantation. The difference in apparent amplitude of accommodation noted

pre-operatively between MSICS and phacoemulsification was eliminated post-

operatively.

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LIMITATIONS OF THE STUDY

1) Though the initial requirement for our sample size was calculated at 120

subjects reaching that target was difficult and we had to settle for the

recalculated number of 81 patients.

2) 25% percent of our patients could not be followed beyond one month due

to time constraints.

3) The phacoemulsification group had many more patients compared to the

MSICS group and could have affected the sub-group analysis.

4) The confounder effect seen in anterior chamber depth analysis has not

been resolved.

5) Some of the sub-group analysis had low power as the study was not

designed to look into that.

6) Amplitude of apparent accommodation as measured by RAF rule is a

subjective test and the lack of complete objectivity can be criticised.

7) There was a problem in our initial design of the study in that, we had not

anticipated that the post-operative anterior chamber depth cannot be

measured by the Nidek optical biometer. So much so, that we had to

change to ultrasound measurements after the first patient.

79 | P a g e

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BJ. Effect of femtosecond laser-assisted cataract surgery on the corneal

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106. Kaufman PL. Accommodation and Presbyopia: Neuromuscular and

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aging human crystalline lens with accommodation. Vision Res. 2005

Jan;45(1):117–32.

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Opt 1992 P 140-2.

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1989 Aug;34(1):15–30.

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APPENDIX – A

IRB APPROVAL LETTER

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APPENDIX – B

PATIENT INFORMATION SHEET

AND CONSENT FORM

Protocol No:

Changes in Anterior Segment Parameters and Amplitude of

Accommodation Following Cataract Surgery.

Name of participant:

You are invited to take part in this study. The information in this document

is meant to help you decide whether or not to take part in the study. Please feel

free to ask if you have any queries or concerns.

What is the study about:

The study is about comparing the changes that occur in the eye before and

after cataract surgery. These include – changes in pupil diameter, depth of the

anterior part of the eye, corneal thickness, length of eyeball, pressure inside the

eye and ability to focus for near.

If you take part, what will you have to do:

If you take part in the study, apart from your routine eye examination, you

will have to undergo a few non-invasive tests free of cost pertaining to the study.

Are there any risks for you if you take part in the study?

As all these tests are non-invasive, so we do not expect any risk or injury

to happen to you as a result of participation in this study; but if you do develop

any side effects or problems due to the study, these will be treated at no cost to

you.

What are the benefits to you if you take part in the study?

There will not be any direct benefit to you if you take part in this study.

You will be prescribed glasses following cataract surgery.

What are the possible benefits to other people?

The study will help us to understand what changes occur in the eye after

cataract surgery, so that we can improve our surgical techniques and help in

future planning.

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Do you have to pay?

You will have to pay only for the tests that are required for the routine

treatment of your eye disease. All additional investigations for the study will be

done free of cost.

Can you decide not to participate?

Your participation in this study is entirely voluntary and you are also free

to decide to withdraw permission to participate in this study. If you do so, this

will not affect your usual treatment at this hospital in any way. Your doctor will

still take care of you and you will not lose any benefits to which you are entitled.

Will your personal details be kept confidential?

The results of this study may be published in a medical journal, but you

will not be identified by name in any publication or presentation of results.

However, your medical notes may be reviewed by people associated with the

study, without your additional permission, should you decide to participate in this

study.

If you have any further questions, you may contact Dr. Gaurab Majumdar,

or Dr. Thomas Kuriakose (Tel: 0416 2281201) or email:

[email protected]

mailto:[email protected]

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CONSENT FORM

Study Number: _______________

Subject’s Initials: _____________ Subject’s Name: ___________________

Date of Birth/Age: ____________

(i) I confirm that I have read and understood the information sheet dated _______

for the above study and have had the opportunity to ask questions.

(ii) I understand that my participation in the study is voluntary and that I am free

to withdraw at any time, without giving any reason, without my medical care or

legal rights being affected.

(iii) I understand that the Sponsor of the clinical trial, others working on the

Sponsor’s behalf, the Ethics Committee and the regulatory authorities will not

need my permission to look at my health records both in respect of the current

study and any further research that may be conducted in relation to it, even if I

withdraw from the trial. I agree to this access. However, I understand that my

identity will not be revealed in any information released to third parties or

published.

(iv) I agree not to restrict the use of any data or results that arise from this study

provided such a use is only for scientific purpose(s).

(v) I agree to take part in the above study.

Signature (or Thumb impression) of the Subject/Legally Acceptable

Representative:

Date: _____/_____/______

Signatory’s Name: ______________________________ Signature:

Signature of the Investigator: ______________________

Date: _____/_____/______

Study Investigator’s Name: _______________________

Signature of the Witness: _______________________

Date: _____/_____/_______

Name & Address of the Witness: _________________________________

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INFORMATION SHEET IN TAMIL

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APPENDIX – C

CLINICAL RESEARCH FORM

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