JOURNAL OF THE COLLEGE OF OPHTHALMOLOGISTS OF SRI … · POTENTIALS (PVEP) IN OPTIC NEUROPATHIES...

• COMBINED USE OF PATTERNELECTRORETINOGRAPHY (PERG) ANDPATTERN REVERSAL VISUAL EVOKEDPOTENTIALS (PVEP) IN OPTICNEUROPATHIES

• ACUTE ANGLE CLOSURE AND ANGLECLOSURE GLAUCOMA

JOURNAL OFTHE COLLEGE OFOPHTHALMOLOGISTSOF SRI LANKAVOLUME 23 No. 2 2017

College of Ophthalmologists of Sri Lanka Annual ISSN 2345-9115

EditorsDr. Mangala Gamage, DO, MS, FRCS

Consultant Eye Surgeon

Dr. Binara Amarasinghe, DO, MS, FRCS

Consultant Eye Surgeon

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Journal Articles

1. Smith JD. Ophthalmology and the medical community.Surv Ophthalmol 1996; 41: 1-30.

2. Smith JD, Jones TS. Ophthalmology and society. SurvOphthalmol 1997; 42: 65-78.

Books3. Smith JD, Jones TS. Public JQ, et al. Ophthalmology and

the World. Boston. Bayside Press, 1997, pp 1-9.

Chapters4. Stevens JT. A transcendentalist’s view of optics, in Smith

JD (ed): Ophthalmology and the Universe, Vol. 6. Part 3.Boston, Bayside Press, 1997. ed 2, pp 230-245.

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JOURNAL OF THE COLLEGE OF OPHTHALMOLOGISTS OF SRI LANKA


JOURNAL OF THE COLLEGE OF OPHTHALMOLOGISTS

OF SRI LANKA

VOL. 23 2017 NO. 2

CONTENTS

Page

Deep Anterior Lamellar Keratoplasty – outcomes at two years follow upK. H. Wickramasinghe, N. P. Costa, R. Walpitagamage, C. J. Kumarage,D. H. H. Wariyapola 47

Pterygium excision leaving bare sclera followed by Mitomycin C applicationK. H. Wickramasinghe, N. P. Costa, R. Walpitagamage, C. J. Kumarage,D. H. H. Wariyapola 49

Acute angle closure and angle closure glaucomaDilruwani Aryasingha 52

Combined use of Pattern Electroretinography (PERG) and Pattern ReversalVisual Evoked Potentials (PVEP) in Optic NeuropathiesD. W. P. Dahanayake, L. P. M. M. K. Pathirage, A. Hangilipola, D. Baminiwatta,S. Senanayake, V. S. Weerasinghe 55

Who should undergo LASIK surgeryC. A. B. Makuloluwa 58

Posterior Chamber Phakic Intraocular Lens implantation for high myopiaat Sri Jayewardenepura General HospitalD. M. M. A. K. Dissanayake, R. S. Walpitagamage, N. P. Costa, P. A. P. I . Perera,D. H. H. Wariyapola 60

Prevalence of dust mite allergy in children with allergicrhinoconjunctivitis in Sri LankaShiranthi Perera, A. Amarasinghe 63

College of Ophthalmologists of Sri Lanka Annual ISSN 2345-9115

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Deep Anterior Lamellar Keratoplasty – outcomes at two years follow up

Deep Anterior Lamellar Keratoplasty – outcomes at two years follow upK. H. Wickramasinghe1, N. P. Costa2, R. Walpitagamage2, C. J. Kumarage1, D. H. H. Wariyapola3

The Journal of the College of Ophthalmologists of Sri Lanka 2017; 23: 47-48

1Senior Registrar in Ophthalmology, 2Post Graduate Trainee in Ophthalmology, 3Consultant Ophthalmologist, SriJayawardenapura General Hospital, Kotte, Sri Lanka.

IntroductionDeep anterior lamellar keratoplasty (DALK) wasintroduced to Sri Lanka in 2009. This surgery enablesthe surgeons to selectively remove the stroma anteriorto the descemets membrane. It allows for more graftsurvival as well as less rejection episodes. DALK isused for conditions like corneal ectasia; Keratoconusetc and anterior stromal scars. In DALK graft size,lamellar dissection technique – big bubble or manualdissection and post-operative management ofastigmatism are all important factors for post-operativeclinical outcomes. This includes the outcomes at 2years following DALK.

MethodDALK done from 2012 January to 2016 June wereenrolled. 155 eyes were included. All patients hadDALK for keratoconus. Post-operative best correctedvisual acuity (BCVA), spherical equivalent (SE) andastigmatism outcomes were analyzed. SPSS softwarewas used in analysis.

ResultsMean age of the patients was 24.12 years. Ages rangedfrom 11 years to 59 years. There were 79 (51%) Males to76 (49%) Females.

All 155 patients achieved 6/12 or better vision by theend of 2 years (Table 1).

Table 1. Distribution of visual acuity with time –percentage of patients shown

Post DALK astigmatism become progressively reducedto lie between -2 to -3 diopters after 1 year (Table 3).Suture manipulation was done to achieve this.

Table 2. Spherical equivalent in diopters withdistribution in time

SE following DALK was flatter initially but becamemore myopic with time (Table 2).

Table 3. Post DALK astigmatism indiopters with time

Lamellar dissection technique was the Anwar bigbubble technique or the layer by layer technique.Anwar big bubble was useful to give better visionearlier to the patients (Table 4, 5).

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The Journal of the College of Ophthalmologists of Sri Lanka

8mm graft size was useful to give better vision earlier(Table 6). However at 2 years follow up there was nodifference with the outcomes of the 7.5mm and 8mmgrafts. This fact was also observed with SE andAstigmatism (Table 7)

Table 4. BCVA distribution in time with ABB

Table 5. BCVA distribution in time with LBL

Conclusion

DALK offers 6/12 BCVA to all at 2 years follow up.Astigmatism is between -2D to -4D. SE is between0 to -1D. ABB offers early visual correction before6 months but a good LBL is as good as an ABB at 2 yrs.8 mm graft gives better vision earlier in the 1st 6 months.At 2 yrs graft size had no effect on BCVA, SE orAstigmatism. 7.5 mm graft gives initial more flattening(hyperopia). Astigmatism is managed with suturemanipulation.

Table 6. BCVA distribution with timein 8mm grafts

Table 8. SE outcomes with time inrelation to graft size

Table 7. Outcomes at 2 years betweenthe graft sizes

7.5 mm graft caused more flattening than the 8mm graft(Table 8).

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Pterygium excision leaving bare sclera followed by Mitomycin C application

Pterygium excision leaving bare sclera followed by Mitomycin C applicationK. H. Wickramasinghe1, N. P. Costa2, R. Walpitagamage2, C. J. Kumarage1, D. H. H. Wariyapola3


1Senior Registrar in Ophthalmology, 2Post Graduate Trainee in Ophthalmology, 3Consultant Ophthalmologist, SriJayawardenapura General Hospital, Kotte, Sri Lanka.

Sutures or glue or autologous blood

PERFECT technique – Pterygium extended removal followed byextended conjunctival transplant

Covered Sclera Methods

4. Conjunctivalautograft

5. Amniotic membrane

6. Scleral patch

7. Lamellar corneal transplant

The most used method is to do pterygium excision and to cover the bare sclera by a conjunctival graft. However,using MMC subconjunctivally following pterygium excision allows pterygium excision to be completed withouta conjunctival graft. This paper describes this surgical technique.

IntroductionA pterygium is a wing-shaped growth of conjunctiva and fibrovascular tissue on the superficial cornea. Excisionof pterygia are mainly considered for visual and cosmetic reasons. There are many methods described for pterygiumexcision and largely they are divided to bare sclera methods and covered sclera methods. Following is a list ofsuch methods.

Bare Sclera Methods1. leaving bare sclera2. leaving bare sclera followed by radio therapy3. Use of MitomycinC(MMC) and leaving bare sclera

Image 1.Marking of the base of the pterygium

Image 2.Excision at the base of the pterygium

Details of surgery

Key words: pterygium, bare sclera, mitomycin C

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The base of the pterygium is marked first. Then thepterygium is excised at the base to leave an area of baresclera. Next the tenon is removed subconjunctivallyaround the exposed area of the bare sclera. Later, thepterygium is lifted off the cornea and the cornea isscraped to clear of any residual pterygial tissue. Oncethe tenon is removed MMC is kept under theconjunctiva for 2 minutes around the bare sclera. MMCshould not be kept on bare sclera. Then the area iswashed off. The surgery is completed leaving baresclera. Patient is continued on ointment antibiotics andsteroids for three weeks.

Image 3. Excision of Tenons

Image 7.Picture of patient at 2 months post pterygium

excision. He had cataract surgery at 1 month postpterygium excision

Image 6.Pre-operative picture of patient with pterygium

Image 5.Insertion of subconjunctival MMCin a cotton, preserving bare sclera

Image 4.Excision at the base of the pterygium

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Pterygium excision leaving bare sclera followed by Mitomycin C application

DiscussionThe most important aspect of pterygium surgery is toprevent recurrences and to prevent sight threateningcomplications of pterygium surgery.

In order to prevent recurrences it is essential to removeas much tenons as possible from around the bare sclerafollowing the excision of the pterygium. The publisheddata by Prof Lawrence Hirst describing his PERFECTtechnique for pterygium excision which demonstratesa large area of tenon and conjunctival excision (1).There was only one recurrence with this techniquefrom close to a 1000 cases (2). However in our surgerieswe have tried to remove as much tenons tissue aspossible from around the bare sclera. It was not asextensive as the PERFECT technique. The concen-tration of MMC is used in this surgery was 0.04%. It isa vital adjunct to prevent recurrences.

MMC should be washed off well following application

so as to leave no residues. Also MMC is not applied onbare sclera. This is to prevent sight threateningcomplications related to MMC.

This technique allows pterygium excision to becompleted faster and also prevents recurrences. Thecomplication profile and the rate of success of thesurgical technique needs to be assessed withaccumulation of data from more cases.

References

1. Hirst LW. Prospective Study of Primary PterygiumSurgery using Pterygium Extended Removal Followed byExtended Conjunctival Transplantation. Ophthalmology2008; 115(10): 1663-72.

2. Hirst LW. Recurrence and complications after 1,000surgeries using pterygium extended removal followedby extended conjunctival transplant. Ophthalmology 2012;119(11): 2205-10.

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Acute angle closure and angle closure glaucomaDilruwaniAryasingha


1Consultant Ophthalmologist, Golden Key Eye Hospital, Rajagiriya, Sri Lanka.

IntroductionAngle closure glaucoma is a major cause of blindnessworldwide, with a particularly high prevalence in someAsian populations. This disease has a familialtendency and is associated with increasing age andhyperopia. Angle closure glaucoma (ACG) results fromappositional or syneachial closure of the anteriorchamber angle leading to reduction in aqueous outflowfacility, intra ocular pressure (IOP) elevation andsubsequent damage to the optic nerve with resultsassociated visual field loss.

There are primary and secondary forms of angle closureglaucoma. In primary angle closure, the mechanismcausing disease is primarily pupillary block, beingeither functional or absolute, while in secondary formsthere are other underlying causes. Both types of angleclosure glaucoma may cause acute dramatic attacks orchronic asymptomatic disease. Foster PJ et al. revisedthe angle closure classification in 2002 and waspublished in British Journal of Ophthalmology.

Angle closure classificationPrimary angle-closure suspect (PACS) or anatomicnarrow angle – An eye in which the anterior chamberangle recess has an abnormally narrow angular width.The peripheral iris is located close to, but not touching,the posterior pigmented trabecular meshwork (TM).No peripheral anterior synaechieaare present. IOP,optic nerve and visual field are normal.

Primary angle closure (PAC) – An eye that has aprimary anatomic narrow angle and evidence thattrabecular obstruction by the peripheral iris hasoccurred, such as peripheral anterior synechiae (PAS),elevated IOP, iris whorling or sectoral atrophy, andexcessive pigment deposition on the trabecular surface.The eye does not have glaucomatous damage of theoptic nerve.

Primary angle closure glaucoma (PACG) – Irido-trabecular contact is present in three or more quadrantsof the drainage angle in the presence of documentedoptic nerve damage and visual field loss.

Secondary angle closure is caused by an underlyingidentifiable pathologic etiology, such as neovascu-larization or uveitis. If angle closure results in elevatedIOP that causes glaucomatous optic disc damage, it isreferred to as secondary angle closure glaucoma.

A large number of risk factors have been identified

• Demographic –• Female sex 2.4 : 1• Age > 60 9.1 : 1• Chinese > Malay or Indian

• Anatomical/Biometric –• Shallow central anteriorly chamber depth

(ACD)• Short axial length• Thick and more anteriorly positioned lens

• Dynamic/physiological –• Prevalence of uveal effusion using UBM is

high in subjects with primary angle closure

• Familial/genetic –• Among first degree relatives higher than the

general population• Prevalence of PACG among first degree

relatives in the white population range from1-12% – higher than the 0.1% prevalence inthe general population

• Novel Risk Factors due to the availability ofanterior segment imaging

• Iris thickness and area• Anterior chamber width• Anterior chamber area (ACA)/volume• Lens vault

Primary angle closure glaucoma is caused by relativepupillary block in the majority of cases. In pupillaryblock, aqueous humor encounters increased resistanceas it flows from the posterior to anterior chamberthrough the iris-lens channel. Some degree of relativepupillary block is present in most phakic eyes. Therisk of pupillary block is highest with a mid-dilatedpupil where there appears to be maximum contact

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Acute angle closure and angle closure glaucoma

between the iris and the lens. In eyes with angle closure,other factors exacerbate the block, such as increase lensvault. The increased pressure gradient across the pupilcauses the peripheral iris to bow forward and coversome or all of the filtering portion of the trabecularmeshwork, resulting in appositional angle closure.Peripheral anterior synechiae form after prolonged orrepeated contacts of the peripheral iris with TM.Another mechanism thought to be important in primaryangle closure is iris angle crowding, which is causedby a thickened peripheral iris filling the space betweenthe TM and angle recess under dark conditions.

aqueous through the pupil because of 360° posteriorsynechiae between the iris and a crystalline lens, anintraocular lens, capsular remnants, or the vitreousface. In secondary angle closure glaucoma withoutpupillary block, angle closure is due to either acontraction of an inflammatory, hemorrhagic, orvascular membrane in the angle leading to PAS, orforward displacement of the lens-iris diaphragm, oftenassociated with ciliary body swelling and anteriorrotation.

DiagnosisThe key to diagnosis of anatomic narrow angle or angleclosure is gonioscopy, which is still the gold standardmethod of angle evaluation. Anterior segment imagingcan assist the diagnosis in certain instances where thecorneal clarity is not sufficient to visualize the anglestructures with gonioscopy. The ideal way to performgonioscopy is in a dark room using a small rectangleof light only as bright as necessary to view the anglestructures, as light can open an appositionally closedangle in about one-third of cases. Dynamic orindentation gonioscopy is essential to differentiateappositional closure from synechial closure. Gentlepressure on the cornea with the goniolens pushes backthe iris and reveals whether the angle can be openedany further, if not, synechial closure is present. Thismaneuver can also help break acute attacks by forcingfluid into the periphery and opening areas of appo-sitional closure.

Occludable angles are typically described as eyes inwhich the posterior, usually pigmented, trabecularmeshwork is seen for less than 90° of the anglecircumference or if the angle width is less than 20°. Athorough history and eye examination are essential indifferentiating between primary and secondary forms.This distinction is crucial as the treatment of each formcan vary greatly.

Anterior segment optical coherence tomography isuseful for objective documentation of angle closure,when findings on gonioscopy are not clear. Also it isuseful for demonstrating dynamic changes in the angleduring light and dark. But less capable of definingspecific etiologies for angle closure due to inability toimage behind the iris.

TreatmentThe mainstays of therapy are medications that lowerintraocular pressure and laser peripheral iridotomyfor any component of pupillary block. Although angleclosure in all its forms is vision threatening, earlydiagnosis and appropriate management can stabilizedisease and minimize vision loss.

A less common cause of primary angle closure isanterior non-pupillary block. This is observed in eyesin which angle closure progresses despite a patentiridotomy, for example, as seen in plateau iris. Plateauiris configuration is characterized by a normal centralanterior chamber depth, flat iris profile, and crowdingof the angle by the iris base. There is a forwarddisplacement of the iris base by anteriorly locatedciliary processes that can lead to subsequent angleclosure. Plateau iris syndrome occurs when an eye withplateau iris configuration develops a closed angle.

Secondary angle closure glaucoma is caused by amyriad of other eye diseases. There are severalsecondary causes of angle closure that involve relativeand absolute pupillary block. In phacomorphic glau-coma, the mass effect of a thickened or intumescentcataract pushes the iris forward and causes patho-logical angle narrowing. Forward displacement of thelens in ectopialentis or microspherophakia can alsopush the iris forward and shallow the angle. Absolutepupillary block occurs when there is no movement of

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There is no curative medical treatment for acute angle-closure. Acute angle-closure attacks must be treatedwith either laser therapy or incisional surgical therapy.The use of eye drops, oral medications (osmotic agentssuch as glycerol or carbonic anhydrase inhibitors suchas acetazolamide), or intravenous medication (mannitol)are temporizing measures designed to bring thepressure down prior to laser/surgical therapy.

Laser peripheral iridotomy

Laser peripheral iridotomy (LPI) is the preferredprocedure for treating angle-closure glaucoma causedby relative or absolute pupillary block. LPI eliminatespupillary block by allowing the aqueous to passdirectly from the posterior chamber into the anteriorchamber, bypassing the pupil. LPI can be performedwith an argon laser, with a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser, or with both.

Sequential Argon YAG Laser PI is used for Asian eyeswith thick brown iris. Advantages include,

• Reduces energy requirements for PI

• Argon thins out iris stroma without generatingclouds of pigment

• Less bleeding

References

1. JLS, Chew PTK. Angle-closure Glaucoma. In: Ophthal-mology, 3rd, Yanoff M, Duker JS (Eds), Mosby, 2009; 1162.

2. Tham YC, Li X, Wong TY, et al. Global prevalence ofglaucoma and projections of glaucoma burden through2040: a systematic review and meta-analysis. Ophthalmology2014; 121: 2081.

3. Foster PJ, Johnson GJ. Glaucoma in China: how big is theproblem? Br J Ophthalmol 2001; 85: 1277.

4. Wong HT, Lim MC, Sakata LM, et al. High-definition opticalcoherence tomography imaging of the iridocorneal angle ofthe eye. Arch Ophthalmol 2009; 127: 256.

5. Quigley HA. Glaucoma. Lancet 2011; 377: 1367.

6. Saw SM, Gazzard G, Friedman DS. Interventions for angle-closure glaucoma: an evidence-based update. Ophthalmology2003; 110: 1869.

7. Vijaya L, Asokan R, Panday M, George R. Is prophylacticlaser peripheral iridotomy for primary angle closure suspectsa risk factor for cataract progression? The Chennai EyeDisease Incidence Study. Br J Ophthalmol 2017; 101: 665.

8. Lai JS, Tham CC, Chan JC. The clinical outcomes of cataractextraction by phacoemulsification in eyes with primary angle-closure glaucoma (PACG) and co-existing cataract: aprospective case series. J Glaucoma 2006; 15: 47.

9. Friedman DS, Vedula SS. Lens extraction for chronic angle-closure glaucoma. Cochrane Database Syst Rev 2006.

10. Lam DS, Leung DY, Tham CC, et al. Randomized trial ofearly phacoemulsification versus peripheral iridotomy toprevent intraocular pressure rise after acute primary angleclosure. Ophthalmology 2008; 115: 1134.

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Combined use of PERG and PVEP in optic neuropathies

Combined use of Pattern Electroretinography (PERG) and Pattern ReversalVisual Evoked Potentials (PVEP) in Optic NeuropathiesD. W. P. Dahanayake1,2, L. P. M. M. K. Pathirage1,2, A. Hangilipola4, D. Baminiwatta3, S. Senanayake3,V. S. Weerasinghe1,2


1Faculty of Medicine, Peradeniya, 2Teaching Hospital, Peradeniya, 3Teaching Hospital, Kandy, 4District Base Hospital,Nawalapitiya, Sri Lanka.

IntroductionOptic neuropathy is a known cause of vision loss encountered by ophthalmologists. The diagnosis is mainlymade on clinical grounds (Behbehani, 2007). Optic neuropathy can be caused by demyelination, inflammation,ischemia, infiltration, compression, and hereditary and toxic/nutritional causes. Pattern reversal visual evokedpotentials (PVEP) is widely recognised as a sensitive measure of optic nerve demyelination and P100 latency hasbeen reported to be significantly prolonged in approximately 90% of patients with a clinical history of opticneuritis. However, it is reported that the VEP abnormalities are nonspecific, and an adjunctive test of macularfunction is needed before an abnormal VEP in a patient with visual symptoms can be assumed to reflect opticnerve rather than macular dysfunction. Pattern electroretinography (PERG) is another electrophysiological testwhich is used to diagnose macular lesions mainly.

ObjectiveTo investigate the effect of various optic neuropathies on PVEP and PERG responses.

The ethical clearance for the study was obtained from the Committee on Research and Ethical Review, Faculty of Medicine,University of Peradeniya, Sri Lanka.

MethodologyWe recruited 16 patients referred to the Neurophysiology Clinic, Teaching Hospital, Peradeniya by a consultantophthalmologist with a provisional diagnosis of optic neuropathy.

Inclusion criteria – patients with a provisional diagnosis of any optic neuropathy optic neuritis (n=11) ischemic optic neuropathy (n=3) traumatic optic neuropathy (n=1) toxic optic neuropathy (n=1)

Exclusion criteria; patients with any retinal disorder

Testing procedure

All the patients were subjected to neurophysiological assessment of vision using PVEP and PERG conforming tothe guidelines of international society of electrophysiology of vision (ISCEV). Nicolet Viking Quest evoked potentialmachine was used to record the PVEP and PERG.

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ResultsThe latencies and amplitudes of PVEP and PERG in patients were compared with the similar results of 30 controlsusing the Students’ t-test.

PVEP latency interpretation

Comparison of mean latencies of PVEP between affected patients and controls

Component Mean absolute latency (SD)ms Significance (p)

N75 88.2 (11.85) 75.8 (7.46) 0.001

P100 115.1 (13.22) 96.0 (5.60) <0.001

N145 144.3 (18.10) 128.3 (12.13) 0.001

Affected patients Controls

In PVEP; all the mean latencies of affected eyes were significantly delayed when compared with the mean latenciesof the controls

PERG latency interpretation

Comparison of mean latencies of PERG between affected patients and controls

In PERG; all the mean latencies of affected eyes were significantly delayed when compared with the mean latenciesof the controls.

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Combined use of PERG and PVEP in optic neuropathies

ConclusionsOur findings suggest that ganglionic cells and otherlayers of macula region of the retina could have beenaffected in this group of patients with suspected opticneuropathies as indicated by P100, N95 and P50latency delays. Therefore, combined use of PERG andPVEP in patients with optic neuropathies is useful todetermine the degree of damage of optic nerve and torule out any maculopathies.

DiscussionIt is said that VEP abnormalities are nonspecific inoptic neuropathies. At present, it is said that N95 waveof PERG provides a measure of ganglion cell functionbut approximately 70% of the P50 wave is alsogenerated by the ganglion cells. The remaining 30%may be generated more distally in retina (Krasodomskaet al., 2010). In a study, done in patients with opticnerve demyelination, PERG was abnormal in

approximately 40% of patients, but in 85% of thosepatients the abnormality was confined to the N95component, in keeping with retrograde degenerationto the retinal ganglion cells (Holder, 2004). However itis said that prolonged P50 latency is seen in somemaculopathies and not due to optic neuropathies(Holder, 2004).

Therefore, in our study prolonged P100 in PVEP andprolonged N95 latency in PERG may be due toretrograde degeneration of the ganglion cells followingoptic neuropathy. But the cause of P50 latency delay isnot yet understood. It may be due to a concomitantinvolvement of the layers of macula other than a pureoptic neuropathy or else in optic neuropathies, maculamay be involved in early stages. However a large scalestudy with more patients with optic neuropathies isneeded to arrive at a definite conclusion. But, thisfinding would be an eye opener for further inter-pretations of PVEP and PERG findings in opticneuropathies.

AcknowledgementThis research was funded by University ResearchGrant; number URG/2016/44/M

References

1. Behbehani R. (2007).Clinical approach to optic neuropathies.Clinical Ophthalmology (Auckland, NZ). 2007; 1: 233-46.

2. Holder GE. (2004).Electrophysiological assessment of opticnerve disease. Eye 2004; 18: 1133-43.

3. Krasodomska K, Lubinski W, Potemkowski A, HonczarenkoK. (2010). Pattern electroretinogram (PERG) and patternvisual evoked potential (PVEP) in the early stages ofAlzheimer’s disease. Documenta Ophthalmologica Advancesin Ophthalmology 2010; 121: 111-21.

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Who should undergo LASIK surgeryC. A. B. Makuloluwa


1Consultant Eye Surgeon, Nawaloka Hospital, Colombo, Sri Lanka.

Introduction

Today, LASIK (laser assisted in situ keratomileusis) isa commonly performed refractive surgery, whichbenefits millions of people with refractive errors world-wide. It is a popular alternative mode of treatment tospectacles and contact lenses. Moreover, it has a highersafety, efficacy, and predictability compared to otherrefractive surgical procedures. However,while manypeople are suitable for LASIK surgery, there are peoplefor whom it may not be suitable and appropriate.Therefore, it is mandatory for the surgeon to select theappropriate candidates for LASIK surgery in order togain better procedural outcome.

There are three factors to consider during the selectionprocess, namely, desire, motivation and suitabilitycriteria.

Desire

Patients who have discontinued contact lens wear dueto various reasons including contact lens-relatedcomplications, will have a great deal of desire toundergo LASIK. Moreover, people who are beingencouraged by patients who have had successfulsurgery will also have an inclination for it.

Motivation

Patients may have motivation to undergo LASIK dueto cosmetic and psychological reasons. As spectaclewear is not required following LASIK, cosmeticappearance and self-confidence may be improved. AsLASIK evidently gives better and higher quality vision,a person may be eligible for certain occupations, sportsand hobbies. Another motivating factor is financialreasons: the long-term cumulative cost of spectaclesand contact lenses will be higher than the cost of LASIKsurgery. In addition, ocular reasons may also be aninfluencing factor. LASIK surgery eliminates thepotential corneal complications and ocular discomfortassociated with contact lens over-wear and inap-

propriate wear. By removing corneal aberrations, theglare from bright lights is reduced, motivating patientsto undergo surgery.

Suitability criteria

To have a successful LASIK procedure, one should meetcertain suitability criteria.

Firstly, corneal thickness should be more than 475µmwith no evidence of keratoconus or any ectasia. Theocular surface as a whole, including the conjunctivaand the lid should be healthy. It is essential that pre-existing dry eye is treated prior to the procedure. Otherocular diseases, such as, glaucoma, cataract, diabeticretinopathy, and macular, retinal and optic nervedisorders, may make one unsuitable for this procedure.Previous major ocular surgery, such as, vitreo-retinal,glaucoma and cataract surgery are contraindications.Nystagmus, strabismus and amblyopia are onlyrelative contraindications.

Refraction needs to be stable for at least one yearand should be within limits for LASIK surgery. Forexample, myopia of less than 10 dioptres, andhypermetropia and astigmatism of less than 5 dioptresare suitable. The predictability of the outcome of theprocedure is reduced if undertaken in patients outsidethese limits, outweighing the cost and risks of surgery.Patients with large pupils may not essentially be a goodcandidate in view of an increased risk of haloes, glareand starburst at night time.

Patients must be 18 years and over to be eligible forsurgery. Although there is no upper age limit, it isimportant to note that when one reaches presbyopicage, the need to wear spectacles for reading. There arecertain treatment modifications that are currentlyavailable to overcome such age-related factors.

In addition to ocular factors, systemic factors also need

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Who should undergo LASIK surgery

to be taken into account, especially conditions that mayaffect wound healing. Uncontrolled metabolic diseases,such as diabetes mellitus, autoimmune diseases, suchas Sjögren’s syndrome, and acquired immunedeficiency syndrome, may be contraindications forundergoing surgery. Moreover, certain medications,such as immunosuppressive agents and isotretinoin,that affect wound healing and the tear film may makea patient unsuitable for surgery. Due to hormonal

changes, pregnancy and breast-feeding are contra-indications.

Finally, as LASIK is a surgical procedure with its ownpotential complications, suitable candidates must bemade aware of these and counselled appropriately.

This is a presentation made at the Annual Congress of theCollege of Ophthalmologists of Sri Lanka in October 2017.

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Posterior Chamber Phakic Intraocular Lens implantation for high myopiaat Sri Jayewardenepura General HospitalD. M. M. A. K. Dissanayake1, R. S. Walpitagamage2, N. P. Costa1, P. A. P. I. Perera3, D. H. H. Wariyapola4


1Registrar, National Eye Hospital, 2Registrar, Colombo North Teaching Hospital, 3Senior Registrar, National EyeHospital, 4Consultant Ophthalmologist, Sri Jayewardenapura General Hospital, Sri Lanka.

IntroductionHigh myopia is defined as a refractive error of -6D ormore. High myopia is a disabling condition to a patientas the world that they see clearly is restricted to a radiusof sixteen centimeters or less. As myopia incidence isrising in each generation (1), improving methods ofvision correction is becoming more importantespecially because it improves the quality of life.

Many types of optical methods of vision correction havebeen proceeded for correction of vision in high myopiaover time. The method usually adopted longest isspectacles. However spectacles used in high myopiahave many disadvantages such as aniseikonia,anisophoria and barrel distortion. The quality of thevision gained is thus reduced. The thick lenses whichare heavy and unsightly, affects self-confidence of thesepatients. Correction of high myopia with contact lensesis better as the distortions are minimal and the cosmeticoutcome is much better. However, the use of contactlenses requires a motivated patient for the properand safe maintenance and wear of the lenses. The useof laser eye surgery such as LASIK (Laser assisted in-situ keratomileusis) and LASEK (Laser epitheialkeratomileusis), for the correction of refractive errorshas become a popular method during the recent past.These surgeries have proven to give good visualoutcomes over time. These procedures are irreversibleand require a minimum corneal thickness pre-operatively. High myopia is usually associated withthin corneas which do not meet this requirement.Therefore, this type of refractive correction has limitedvalue in very high myopic patients.

Phakic Intra Ocular Lenses (pIOL) were first introducedin the 1950s by Dr. Strampeli. These lenses haveevolved slowly over the past seventy years as therewere many serious issues associated with the procedureinitially. Currently there are two types of intra ocularlenses used for phakic patients. The first typedeveloped, the anterior chamberpIOLs, lead toglaucoma and endothelial decom-pensation. The onlyFDA approved design is the iris-claw ACIOL Verisyse(Abbott Laboratories Inc, Abbott Park, IL, USA). It is

branded in Europe as Artisan (Ophtec BV, TheNetherlands).

Posterior chamber pIOLs were first introduced in the1986 by DrFydorov. It was made with a new lensmaterial called collamer which was developed by StaarSurgical, Monrovia, CA, USA. These lenses are placedbetween the crystalline lens and the iris. The lens vaultsover the anterior capsule of the crystalline lens withouttouching it. These proved to have much less endothelialdecompensation as well as glaucoma. However therewas cataract formation associated in the initial perioddue to lens touch by the IOL. A deep anterior chamber(Anterior chamber depth > 3mm) and a good pre-operative endothelial count >2500 cell/mm2 are pre-requisites for these patients to minimize postopera-tive complications. The visual outcomes have beenextremely satisfactory to the patients.

Posterior chamber pIOL insertion is a reversibleprocedure and can be removed when the patientdevelops a cataract later.

Since 2015, pIOL insertion surgery has been carriedout at Sri Jayewardenapura General Hospital.

Objective and methodologyThe objective of this study is to describe the refractiveand surgical outcomes of patients who underwentposterior chamber intra ocular lens insertion surgeryat Sri Jayewardenapura General Hospital between1st July 2016 and 30th June 2017.

Nine eyes belonging to seven patients were analyzedretrospectively with regards to preoperative refraction,immediate postoperative refraction, intra ocularpressure and vault height. The vault height wasmeasured with anterior chamber Optical coherencetomography (Visante). The lenses inserted were PCIOLVisian ICL (intraocular collamer lens) V4c design. ThispIOL differs from the V4 design in that it has a centralhole to allow aqueous humor to pass through from theposterior chamber to the anterior. This eliminates therequirement of a peripheral iridotomy. All surgerieswere performed by a single surgeon.

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Posterior Chamber Phakic Intraocular Lens implantation for high myopia at Sri Jayewardenepura General Hospital

ResultsPatients were between 18 years and 42 years. 3 eyesbelonged to 3 female patients while 6 belonged to 4male patients.

The post-operative vault heights of the patients werebetween 0.29 mm and 1.2 mm (Table 1).

The mean preoperative spherical equivalent was-16.27D. The minimum level of spherical equivalentin this myopic population was -9.25D. The meanpostoperative spherical equivalent was -0.11D.

None of the patients had a significant postoperativeintra ocular pressure rise. The postoperative IOPchange had a mean of ±2.5 mm.

The patient satisfaction postoperatively was noted tobe very high with the quality of vision and the visualacuity gained and most patients opted to undergo thesame procedure for the second eye (two had alreadydone so.)

DiscussionAlthough the total number of posterior chamber pIOLimplantation surgeries that have been performed inSri Lanka are limited, the results of the surgeries arepromising.

The postoperative vault height; the height between theanterior capsule of the crystalline lens and the ICL,was found to be best when between 0.2 mm and 1mm(Image 1). A reduced height would increase theincidence of crystalline lens touch by the ICL and causecataract formation (2). Vise-versa, if the vault height istoo high, the chances of endothelial decompensation,pigment dispersion, pupillary block as well as a risein intra ocular pressure would occur. A deep anteriorchamber prior to surgery is necessary to get a goodpostoperative vault height and thereby preventpostoperative complications.

Patient number Post-operativevault height (mm)

1 0.45

2 0.53

3 0.53

4 0.29

5 0.35

6 0.55

7 1.2

8 0.53

9 0.91

Table 1. The postoperative vault height

The mean vault height was 0.59 mm.

The postoperative refraction was measured in theimmediate postoperative period. The preoperative andpostoperative spherical equivalents of the patients aregiven in Table 2.

Patient number Preoperative Postoperativespherical spherical

equivalent equivalent

1 -21.5 -3.6

2 -12.75 +1

3 -18.6 0

4 -9.25 -0.1

5 -16.4 +1

6 -15.5 +1

7 -14.25 +0.6

8 -19.0 -1.12

9 -19.25 0

Table 2. Preopertive and postoperativespherical equivalent

Graph 1. Comparison between preoperative andpostoperative spherical equivalent in each patient.

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A meta-analysis and review on effectiveness, safety,and central port design of the intraocular collamer lensin 2010 identifies the vault height as a risk factor forvault height than an adverse event as only a percentageof eyes beyond predefined values of vault heightexperience adverse events (3). In our study 8 out ofnine eyes had a good postoperative vault height. Oneeye had a 1.2 mm vault height. This particular patienthad a very deep anterior chamber depth prior to surgery(4.14 mm). Therefore the high postoperative vaultheight is expected and long term complications can beexpected to be minimal.

The postoperative intra ocular pressure did not showa significant rise. The risk of angle closure glaucoma isless in posterior chamber phakic IOLs than anteriorchamber phakic IOLs. A study done in 2010 on 100eyes which had undergone phakic intraocular lensimplantation with the V4c model with the central hole,did not detect a statistically significant change inintraocular pressure 1 day, 1 week and after 1 monthpostoperatively.

The postoperative refraction of these patients shows amean of 0.11D. 3 eyes had a spherical equivalent within±0.5D and 7 eyes were within 0.7D. Therefore therefractive errors were corrected very close to emme-tropia. Alfonso JF et al reports a mean sphericalequivalent decrease from -11.17 diopters (D) ± 3.40 (SD)preoperatively to -0.88 ± 0.72 D 5 years postoperativelyon 188 eyes (4).

One eye which had a very high preoperative refractiveerror of -21.5D had a post op error of -3.6D. Withsecondary Lasik surgery the remaining error can becorrected further.

The longterm safety and predictability of posteriorchamber IOLs were demonstrated by Igarashi et al (5).They studied 41 eyes for 8 years after surgery. 68.3%and 85.4% of the eyes were within 0.5 and 1.0 D,respectively, of the targeted correction. Manifestrefraction changes of -0.32 ± 0.73 D occurred between1 month and 8 years. The mean endothelial cell lossfrom preoperative levels was 6.2% at 8 years. Two eyes(4.9%) developed clinically significant symptomatic

cataract during the follow-up period. Simultaneouslens extraction and phacoemulsification with IOLimplantation was successfully performed in these 2eyes.

The patients were extremely satisfied with their post-operative vision and this visual outcome has beendescribed as “superb” (6).

ConclusionPosterior chamber pIOL implantation surgeries donein Sri Lanka are limited in number. But the surgeriesdone upto now show satisfactory results both visuallyand anatomically and are comparable to surgeriesperformed in other centres in other countries. Posteriorchamber pIOL insertion seems to be a safe andpredictable surgical management option for highmyopes even in Sri Lanka. However long term followof these patients, are required.

Bibliography

1. Dolgin E. The myopia boom. Vol. 519, Nature. England2015; 276 - 8.

2. Schmidinger G, Lackner B, Pieh S, Skorpik C. Long-termchanges in posterior chamber phakic intraocular collamerlens vaulting in myopic patients. Ophthalmology. UnitedStates; 2010; 117(8): 1506-11.

3. Moole H, Jaeger A, Bechtold ML, Forcione D, Taneja D,Puli SR. A Meta-Analysis and Systematic Review Successof Extracorporeal Shock Wave Lithotripsy in ChronicCalcific Pancreatitis Management. Pancreas 2016; 45(5):651-8.

4. Alfonso JF, Baamonde B, Fernandez-Vega L, Fernandes P,Gonzalez-Meijome JM, Montes-Mico R. Posterior chambercollagen copolymer phakic intraocular lenses to correctmyopia: five-year follow-up. J Cataract Refract Surg. UnitedStates; 2011; 37(5): 873-80.

5. Igarashi A, Shimizu K, Kamiya K. Eight-year follow-up ofposterior chamber phakic intraocular lens implantation formoderate to high myopia. Am J Ophthalmol. United States;2014; 157(3): 532-9.e1.

6. McLeod SD. Long-term Clinical Outcomes and CataractFormation Rates After Posterior Phakic Lens Implantationfor Myopia. JAMA Ophthalmol United States 2016.

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Prevalence of dust mite allergy in children with allergic rhinoconjuctivitis in Sri Lanka

Prevalence of dust mite allergy in children with allergic rhinoconjunctivitisin Sri LankaShiranthi Perera1, A. Amarasinghe2


1Consultant Ophthalmologist, 2Consultant Paediatrician and Clinical Allergist.

IntroductionAllergic rhinoconjunctivitis is a common chronicdisorder in children. It does not cause nasal and ocularsymptoms only (such as congestion and sneezing) butmay also cause general complaints such as fatigue andcough. It can also cause learning problems and has agreat impact on quality of life. Uncontrolled allergicrhinoconjunctivtis may aggravate the symptoms ofasthma. Although classic “hay fever” is easilyrecognized in children who have a runny nose, snee-zing, and itchy eyes, diagnosis of allergic rhinoconjunctivitis is often missed in children with perennialnasal congestion.

Although allergic patients often present with rhinitis,asthma, urticaria or eczema, ocular symptoms may bethe initial and the most prominent manifestation ofthe allergic response. Ocular allergies are quitecommon and is supposed to affect 5-22% of the popu-lation. The eye is a common site for the development ofan allergic inflammatory disorder. The most commonsign of allergic conjunctivitis is a red eye. Other com-mon symptoms are watery eyes, itching, redness,soreness, swelling or stinging. Ocular allergy canpresent with various allergic manifestations andpresentations such as: a) seasonal allergic conjunc-tivitis (SAC), being the most common presentationb) perennial allergic conjunctivitis (PAC), c) giantpapillary conjunctivitis (GPC), d) vernal kerato-conjunctivitis (VKC) and e) atopic keratoconjunctivitis(AKC). Pharmacological treatment mainly includes theprescription of topical ocular mast cell stabilizers orantihistamines and in more severe cases cortico-steroids, immunosuppressant drugs and immuno-therapy.

The evaluation of such patients with skin prick tests(SPTs) is usually overlooked in most cases. SPTsrepresent an immediate IgE mediated allergic reactionand may provide clear evidence for the diagnosis ofspecific allergic manifestation. The identification of the

degree of sensitization to the most common allergensby this test can provide a useful insight to exacerbatingfactors of allergic conjunctivitis.

The aim

The aim of the present study was to identify the pre-valence of dust mite allergy in children with allergicrhinoconjuctivitis in Sri Lanka. This is a prospectivestudy regarding children with symptoms of allergicdisease who were referred to an outpatient allergy clinicbetween January 2014 to December 2015. Theycompleted relative questionnaires concerning theirallergic condition. It provided information with regardto allergic symptoms (wheeze, dyspnea, cough, sputum,rhinorrhea, sneezing, tearing, eye-itching, red eye),allergic background as well as previous medicaldiagnoses and therapies. The screening question forallergic conjunctivitis referred to watery, red anditching eyes.

Following the questionnaire for each entity (asthma,allergic rhinitis, allergic conjunctivitis) the diagnosiswas confirmed by a specialist. The patients who wereincluded in the study had allergic conjunctivitisconfirmed by an ophthalmologist and were dividedinto 4 groups. The criteria used were the existence ofallergic conjunctivitis alone or with other allergic co-morbidities. The patients then underwent Skin PrickTesting (SPT) after consent. Out of the 44 inhaled andfood allergens, the 10 most relevant allergens accordingto the history of a individual patient were tested. pollenwas not tested as prevalence studies of pollen in SriLanka has not yet been performed. Out of the 44allergens in the penal allergens for house dust mite,cat and dog dander, cockroach, and food such as egg,pineapple, prawns were included.

The patients were instructed to avoid per or topicaluse of antihistaminic drugs or steroids 5 days prior tothe test. The SPTs were considered positive when thewheel diameter was 3 mm and redness 10 mm, 15minutes after the test.

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Study design

All 82 children were referred to an allergy clinic withsymptoms of allergic disease between Jan 2014 to Dec2015 to do the skin prick testing. Of them all com-plained of perennial symptoms and seasonalvariations were difficult to find. The age of the studypopulation was 5 years to 14 years and 80% of themwere 8 years or above. Of the 71 the who hadrinoconjunctivitis 65 had rhinitis and conjunctivitis,6 had only conjunctivitis.

Skin prick test

Allergen Percentage

Dust mite 65.7%

House dust 40.8%

Cockroaches 30.3%

Pineapple 11.1%

Egg 10.8%

Dog 8.3%

Table 2. Percentage of the children withallergic rhinoconjunctivitis demonstrating

allergy to 6 main allergens

Of this population 65.7% was positive for dust miteallergen proven by the skin prick test results. Reactivityfor other allergens were significantly less. Of thepatients showed allergy to dust mites 73% hadrhinoconjunctivitis with asthma.

ConclusionDust mite allergy plays a significant role in causingallergic rhinoconjunctivitis in Sri Lanka and is oftenassociated with asthma.

References

1. Weeke ER. Epidemiology of hay fever and perennial allergicrhinitis. Monogr Allergy 1987; 6: 1-20.

2. Williams DC, Edney G, Maiden B, Smith PK. Recognitionof allergic conjunctivitis in patients with allergic rhinitis.World Allergy Organ J 2013; 6(Supp1): 4.

3. Bielory L. Allergic and immunologic disorders of the eye.part II: ocular allergy. J Allergy Clin Immunol 2000; 6: 1019-1032. doi: 10.1067/mai.2000.111238.

Table 1. Study sample

Study sample 82

Rhinitis/conjunctivitis 71

Rhinitis and conjunctivitis 65

Conjunctivitis only 6

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