REFRACTIVE SURGERIES

Dr.Jyoti ShettyMedical Director,Bangalore West Lions Superspeciality Eye Hospital

CLASSIFICATION

REFRACTIVE SURGERIES

CORNEA BASED LENTICULAR BASED COMBINED(BIOPTICS)

-R.K.-PRK-LASIK-EPILASIK-LASEK-Conductive Keratoplasty-Corneal Inlays and rings

-Clear Lens extraction for myopia-Phakic IOL- Prelex Clear Lens Extraction with use of Multifocal IOL’s

Combination of the two

LASIK(Laser Assisted In Situ Keratomileusis)

Procedure using laser to ablate the tissue from the corneal stroma to change the refractive power of the cornea

Types of lasers used- Excimer-Excited dimer of two atoms

-an inert gas(Argon)

-Halide(Fluoride)

which releases ultraviolet energy at193nm for corneal ablation

Non-Excimer solid state lasers- 210nm Q switched diode pumped laser (laser

off) 213 nm Q switched diode pumped

laser(Pulsar)

Advantage of Non-Excimer solid state lasers- No toxic excimer gases Wavelength closer to absorption peak of corneal

collagen—less thermal and collateral damage Better pulse to pulse stability Not absorbed by air,water,tear fluid-so less

sensitive to humidity or room temperature No purging with inert gases required.

Patient selection

Patients need to be fully informed about potential risks,benefits and realistic expectations

Age should be above 18 years Refractive status should have been stable

for at least 1 year. Current FDA approval-

Myopia-upto -12D Hyperopia –upto +6D Astigmatism-upto 7D

CCT such that minimum safe bed thickness left(250-270µ).Post op Corneal thickness should not be <410µ.

Cornea not too flat or steep.<36D or>49D(Poor Optics).

CONTRAINDICATIONS

Systemic factors- Poorly controlled IDDM Pregnancy/lactation Autoimmune / connective tissue disorders(RA,SLE,PAN

etc) Clinically significant Atopy,Immunosuppressed patients Keloid tendency(esp PPK) Slow wound healing-Marfans,Ehler-Danlos Systemic Infection-(HIV,TB) Drugs-Azathioprene,Steroids(Slow wound healing)

CONTRAINDICATIONS

Ocular Factors- Glaucoma,RP(Suction Pressure-ON

damage,Blebs) Previous h/o RD or f/h of RD. One eyed individual Pre-existing dry eye,Keratoconus.pellucid

marginal degeneration,Superficial corneal dystrophy,RCE,Uveitis,early Lenticular changes

h/o Herpetic Keratitis(one year prior to surgery)

PREOPERATIVE EVALUATION PRIOR TO LASIK

Record UCVA and BCVA Snellens V/a Dry and wet manifest refraction(with 1%

cyclopentolate) Pupillometry-Infrared Pupillometer -Aberrometer Large pupil-Increased HOA perceived

so increased glare -Can change Optic Zone

Slit Lamp Examination- Rule out blepharitis, miebomianitis,

pingecula, Pterygium,corneal neovascularization

Other contraindications for LASIK. IOP by applanation Dilated Fundus Examination to role out

holes ,tears.

Tear film asessment-Schirmers,TBUT and Lissamine staining

Blink Rate-(Normal---3-7/min) Corneal Topography-

Scanning slit/placido disc Stop RGP lenses 2 weeks prior and soft lenses I

wk prior To rule out early Keratoconus and other ectasias For mean K values

Pachymetry -For CCT (Ultrasound/Optical)

Contrast Sensitivity testing for pre-operative baseline.

BASIC STEPS AND MACHINE SPECIFICATIONS

Topical anasthesia-Proparacaine 0.5%, Lignocaine 4%.

Surgical Painting and draping(Lint Free).

Lid speculum with aspiration. Corneal marking-Orientation of free

cap

Creation of flap-

1st Step-Creation of suction by suction pump to raise the IOP to 65 mm Hg which is necessary for the microkeratome to create a pass and resect the corneal flap.

This is crosschecked with Barraquers tonometer.

2nd step-Resection of corneal flap

Microkeratome Femtosecond Laser(Intralase)

Microkeratome- Uses Disposable blades Blade Plate can be set at

120µ,140µ,160µ and180µ. Nasal or superiorly hinge flaps can be

created. Eg.Hansatome,ACS,Carriazo Barraquer,

Moria.

Femtosecond Laser for Flap- Creates photodisruption using femtosecond solid

state laser with wavelength of 1053nm. Needs lower vacum. Very short pulse with spot size of 3µ-High

precision cutting device. Any hinge can be made Can make flaps as thin as 100µ(Sub Bowmanns

Keratomileusis)

Flap has vertical edges –so reduced epithelial ingrowth.

Microkeratome flap thicker in periphery and thinner in the centre.Not so with Intralase(Planar).

3rd Step-Delivery of Laser- After flap is lifted, laser is applied to the

stroma according to the ablation profile calculated by the machine.

Laser beam is delivered by the following ways depending on the machine-

Beam Delivery

Broad Beam Scanning Slit Beam Flying Spot

Most machines employ a flying spot to deliver laser with the help of incorporated eye tracker.

4th step-Reposition Of the Flap- After irrigating interface ,flap reposited Adhesion test-Striae test

ABLATION PROFILES

Wavefront Guided or customized ablation-to improve quality of vision by correcting higher order aberrations.

-Wavefront analysis on entire eye

done by –Hartmann Shack

-Tracy

ABLATION PROFILES

Aspheric Ablation-Normal LASIK converts prolate cornea to oblate structure.(Central flattening,steep in periphery.) which induces higher order aberrations.

To reduce this and preserve the prolate structure,’Q’ value is calculated and altered to give a more aspheric ablation.

COMPLICATIONS OF LASIK

Under/over correction and regression (over time).

Post –op Keratectasia Presents 1-12 months Progressive regression Treatment-RGP,Corneal transplant. Prevention- Leave residual stromal bed -Do surface ablation -Don’t violatecorneal topography

diagnosis of forme-fruste keratoconus

COMPLICATIONS OF LASIK

Night vision disturbances-Haloes/Glare Decenteration and central islands. Post Lasik Dry eye-

Fluctuating vision,SPK Temporary neuropathic cornea Confocal microscopy-90% reduction in corneal

nerve fibres-regeneration by 1 year. Rx-Preservative Free lubricants

COMPLICATIONS OF LASIK

Post op Glaucoma(Pseudo DLK)-Steroid induced.

Vitreoretinal Complications- Increased risk of RD due to alteration of

anterior vitreous by suction ring-Risk 0.08%.

PVD(0.1% Risk) Macular Hemorrage(0.1% Risk)

COMPLICATIONS OF LASIK

Flap Complications- Button Hole-If

K>50D,due to central corneal buckling.

.

Irregular thin flap-Inadequate suction/old blade

Short Flap-Hinge encroaches on visual axis-Due to jamming of microkeratome with hair/FB

SHORT FLAP

Free Cap-Due to flat pre –op K(<38D).

.Flap undulations- Macrostriae-Linear lines in

clusters,seen on retroillumination.

Causes-Incorrect position of flap

-Movement of flap after LASIK

Rx-Lift flap

-Rehydrate and float it back

-Check for flap adhesion

MACROSTRIAE

Microstriae-Flap in position but fine wrinkles seen superficially

-Due to large myopic ablation

-Rx- Observe.They resolve spontaneously

MICROSTRIAE

Bleeding during flap cutting due to corneal neovascularization in contact lens users

Interface Inflammation(Sands Of sahara/DLK)-Non-Infective inflammation at the interface seen in 1st week after LASIK. Diffuse,confluent,white granular material

at the interface 1-7 days after LASIK. Slight CCC No AC reaction Reduced Visual acuity

Grade 1-

Focal involvement - Normal V/A.

Rx Intensive topical steroids.

II – Diffuse involvement –Normal V/A.

Rx-Add systemic steroids.

III – Diffuse confluent granular deposits-

Reduced V/A.No AC reaction.

Rx-Same as above+Antibiotics

IV - Diffuse confluent granular deposits +intense central striae.

Marked Reduced V/A

Rx-Interface irrigation + above

Causes-Proposed Theory Bacterial cell wall endotoxin Cleaning solution toxicity Talc from gloves Miebomian secretions

Infection-Potential complication as any surgical procedure

Epithelial ingrowth-Presents 1-3 months after LASIK. Causes-Epithelial cells trapped under flap Risk factors-Peripheral epithelial defects

-Poor flap adhesion

-Buttonholed flaps

-Repeat LASIK

Classification- GRADE 1-Faint white line <2mm from flap

edge GRADE 2-Opaque cells <2mm from flap

edge with rolled flap edge GRADE 3-Grey to white fine opaque line

extending >2mm from flap edge. GRADE 4-If ingrowth >2mm from edge with

documented progression—Lift flap and remove the sheets of epithelium.Can use MMC.

EPILASIK / LASEK

Anterior stroma of cornea (ant. 1/3 rd)

has stronger interlamellar connections than post. 2/3rd.

So surface ablation preserves the structural integrity better than LASIK especially in the correction of moderate to high myopia.

LASEK-Camellins Technique- 20% absolute alcohol used for 20-35s. To

raise epithelial flap. Flap reposited after ablation

EPILASIK- Epithelial keratome used to lift epithelial flap of about 60-80µ thick.

Epithelial keratomes use

- PMMA blades

-Metal Epithelial Separator

CONDUCTIVE KERATOPLASTY

Uses mild heat from radiofreqoency waves to shrink collagen in the periphery of the cornea---This steepens the paracentral cornea.

Used for hyperopia (1 – 2.25D) and presbyopia.

C.K. spots are applied with a probe in rings with a dia. Of 6/7/8 mm.

8 spots are given in each diameter ring.

5mm6 7

Drawbacks- Regression and retreatment in 100%

cases after 6 months. Induced cylinder >1D reported in many

cases. Usually done in one eye—Many have

intolerance to monovision.

CORNEAL INLAYS

Increase the depth of focus by using pinhole optics.

Inlays have 1.6mm centre with 3.6mm surround.

Near vision improves by 1.5D with no loss of distant vision.

Used in the non –dominant eye. These are hydrogel based.Placed in a

tunnel 200-400 µ deep in centre of cornea.

AcuSof Corneal inlay

Phakic IOLs

An intra-ocular lens is placed inside the eye in front of the patient’s natural lens.

These are available in three types1. Anterior chamber angle fixated IOL – Nuvita

(Bausch & Lomb), Kelman duet, I care (corneal), Vivarte (Ciba vision)

2. Iris supported phakic IOL – Verisyse/ Artisan (AMO/Ophtec)

3. Plate lens that fits between the iris & the crystalline lens – Starr implantable contact lens (ICL), PRL (Ciba).

Indications

Age above 18 years Stable refraction for one year Patients not suitable for LASIK/LASEK

due to high powers or thin corneas AC depth 3.0 mm Endothelial count >2000cells/cumm No other ocular pathology

Contraindications Myopia other than axial myopia Corneal dystrophy/ Endothelial cell count

<2000cells/cumm Anterior chamber depth less than 3.0mm History of uveitis Presence of anterior/posterior synechiae Glaucoma or IOP higher than 20 mmHg Evidence of nuclear sclerosis or developing

cataract Personal or family history of retinal detachment Diabetes mellitus

Angle supported anterior chamber phakic IOLs – Rigid lenses

IOL NuVita MA20 ZSAL-4 Phakic6

Company Bausch & Lomb Morcher M & C

Prev. model ZB5M / ZB5MF (Baikoff)

ZSAL 1-3 ________

Material PMMA PMMA PMMA

Optic 5.0 mm 5.8 mm 6.0 mm

Eff.opt.zone 4.5 mm 5.3 mm ??

Haptic + optic 12 -13.5mm 12.0/13.5mm 12 – 14mm

Diopters (D) - 3.0 to – 23.0 D -20.0 to +10.0D Plano concave (-20

to -3.0)

Convexo-concave (-2.5 to +4.5)

Biconvex (+5 to +10)

- 2.0 to -25.0D

+2.0 to +10.0D

Angle supported anterior chamber phakic IOLs – Foldable IOls

IOL Vivarte I CARE Kelman Duet The Vision Membrane

Company Ciba vision Corneal (france)

Vision membrane technologies

Material Hydrophillic acrylic (RI = 1.47)

HEMA 26% Optic- Silicone Haptic PMMA

Silicone

Optic 5.5 mm 5.75 mm 5.5 mm 7.0 mm

Haptic + optic

12-13 mm 12-13.5 mm 12-13.5 mm

Diopters (D) -7.0 to -25.0 D -20.0 to +10.0D injectable lens

-8.0 to -20.0 D

Anterior Chamber Phakic IOL

Kelman Duet phakic IOL

Two piece phakic IOL. The PMMA haptic is first snaked through a 1.5mm incision. The silicone optic is then compressed & inserted. Once the optic unfolds in the anterior chamber the two tabs on either side of the optic are snapped into projections on the haptic. The main advantage of this lens is that the optic can be exchanged with a new one if the patient’s refraction changes.

Iris fixated phakic IOL – Verisyse Phakic IOL

Most commonly used phakic IOL One-piece design

Verisyse Phakic IOL

Pre-op assesment for phakic IOL

Refraction – Objective & subjective acceptance at 12mm vertex distance

Anterior chamber depth – from epiuthelium to endothelium

Anterior & posterior segment examinations K-reading & Topography – Orbscan-II Intra-ocular pressure White to white measurement Specular microscopy

Veriflex (artiflex)

Foldable iris claw lens. It is a modification of Verisyse (Artisan) phakic IOl.

Posterior chamber lenses

These phakic IOLs are placed in the posterior chamber between the iris & the crystalline lens. These are

1. Starr ICL

2. Cibavision PRL

STAAR ICL

The STAAR Collamer ICL and the TORIC ICL are posterior chamber phakic intraocular lenses. Made of Collamer, STARR’s proprietary collagen copolymer (colagen/HEMA), the lens rests behind the iris in the ciliary sulcus.

Procedure

The lens is gently folded and injected into the anterior chamber through a 3.0 mm, temporal, clear corneal incision. The ICL is then carefully positioned by manipulating the footplates of the lens posterior to the iris plane and and into the sulcus. Pre-operative YAG iridotomy is essential.

Complications

ICL decentration Pupillary block Pigment dispersion Subcapsular cataract

Advantages of phakic IOLs over laser corrective procedures

A higher range of refractive errors can be corrected Reversible: Phakic IOL implantation is a potentially

reversible procedure Safe: No structural changes are induced. Hence it is

safe in any eye with high error & also thin corneas. Better quality of vision: Quality of vision (contrast

sensitivity) is better than the laser refractive procedures in eyes with higher refractive errors and no induced higher order aberrations. There is also a considerable improvement in BVCA with these lenses because of the magnification effect.

Highly skilled procedure: Prevents misuse of the procedure.

Bioptics Bioptics is a combination of phakic IOL and

LASIK. Bioptics is done for the correction of the residual spherocylindrical power when a spherical implant is used.