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REFRACTIVE REFRACTIVE SURGERIES SURGERIES Dr. NEHA Dr. NEHA PATHAK PATHAK 2 2 nd nd year PG year PG Resident Resident Deptt. of Deptt. of Ophthalmology Ophthalmology Govt. Medical Govt. Medical

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Page 1: refractive surgeries

REFRACTIVE REFRACTIVE SURGERIESSURGERIES

Dr. NEHA PATHAKDr. NEHA PATHAK 22ndnd year PG year PG ResidentResident Deptt. of Deptt. of OphthalmologyOphthalmology Govt. Medical Govt. Medical College, KotaCollege, Kota

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Eye’s refractive power determined Eye’s refractive power determined by 3 variables - by 3 variables - 1. Power of the 1. Power of the corneacornea 2. Power of the lens 2. Power of the lens 3. Length of the eye 3. Length of the eyeEMMETROPIA EMMETROPIA

- Optically normal - Optically normal eyeeye

- Image of the - Image of the object being object being viewed is focused viewed is focused on retinaon retina

- Resulting in clear - Resulting in clear & sharp vision& sharp vision

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AMMETROPIAAMMETROPIA – A condition of refractive – A condition of refractive errorerror - Causes blurred vision - Causes blurred vision as image is as image is not focused on retina not focused on retina1. Myopia1. Myopia

- Near-sightedness- Near-sightedness- Image is focused Image is focused

in front of retinain front of retina

2. Hyperopia2. Hyperopia

- Far-sightedness- Far-sightedness

- Image is focused - Image is focused behind retinabehind retina

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3. Astigmatism3. Astigmatism – Refraction varies in different meridia – Refraction varies in different meridia

- Rays of light entering eye can’t - Rays of light entering eye can’t converge to converge to

a point focus but form focal linesa point focus but form focal lines

4. Presbyopia4. Presbyopia – Eye sight of old age – Eye sight of old age

- Physiological insufficiency of - Physiological insufficiency of accomodation accomodation

leading to progressive fall in near visionleading to progressive fall in near vision

- Mechanism : - Mechanism :

1. Senile lens hardening 1. Senile lens hardening

2. Secondary relaxation of equatorial 2. Secondary relaxation of equatorial zonules zonules

caused by continuous growth of lenscaused by continuous growth of lens

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PUPIL SIZE & CENTRATION OF PUPIL SIZE & CENTRATION OF REFRACTIVE PROCEDURESREFRACTIVE PROCEDURES

Rays of light from a point source are Rays of light from a point source are refracted by the area of cornea overlying the refracted by the area of cornea overlying the entrance pupilentrance pupil. This area is c/a the . This area is c/a the corneal corneal optical zoneoptical zone..

Entrance pupilEntrance pupil- Virtual image of - Virtual image of anatomical anatomical pupilpupil formed by magnifying effect of the formed by magnifying effect of the cornea – larger & closer to cornea.cornea – larger & closer to cornea.

Optical zone in a keratorefractive procedure : Optical zone in a keratorefractive procedure : “The area of central cornea that bears the “The area of central cornea that bears the refractive change caused by the surgery”.refractive change caused by the surgery”.

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FACTORS DETERMINING FACTORS DETERMINING CENTRATION OF CENTRATION OF KERATOREFRACTIVE PROCEDURESKERATOREFRACTIVE PROCEDURES

Foveal photoreceptors Foveal photoreceptors orient themselves towards orient themselves towards centre of the pupil (Stiles-centre of the pupil (Stiles-Crawford effect), even if Crawford effect), even if entrance pupil becomes entrance pupil becomes eccentric.eccentric.

Pupillary dilatation under Pupillary dilatation under mesopic & scotopic mesopic & scotopic conditions, beyond the conditions, beyond the edge of the optical zone edge of the optical zone causes edge glare & haloescauses edge glare & haloes

=>=>Favour the centration of Favour the centration of KR procedures on the pupil KR procedures on the pupil instead of the elusive instead of the elusive visual axisvisual axis

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CLASSIFICATION OF REFRACTIVE CLASSIFICATION OF REFRACTIVE PROCEDURESPROCEDURES

R.K. PRK LASIK EPILASIK LASEK Conductive

Keratoplasty Corneal Inlays

and rings

REFRACTIVE SURGERIES

CORNEA BASED LENTICULAR BASED COMBINED(BIOPTICS)

Clear Lens extraction for myopia

Phakic IOL Prelex Clear

Lens Extraction with use of Multifocal IOL’s

• Combination of the two

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KERATOREFRACTIVE SURGICAL KERATOREFRACTIVE SURGICAL PROCEDURESPROCEDURESLOCATION ADDITION SUBTRACTIO

NRELAXATION COMPRES

SION

SUPERFICIAL 1.EPIKERATOPHAKIA2.SYNTHETIC EPIKERATOPHAKIA

1.PRK2 LASEK3.Epi-LASIK

---------- CORNEAL MOLDING

INTRASTOMAL 1.KERATOPHAKIA2.INTRACORNEAL LENSES3.PINHOLE APERTURES

1.LASIK2.WAVEFRONT GUIDED LASIK3.IntraLASIK (IntraLase)

LAMELLAR KERATOPLASTY

PERIPHERAL INTRACORNEAL STROMAL RING

WEDGE RESECTION

1.RADIAL KERATOTOMY2.ARCUATE KERATOTOMY

1.THERMOKERATOPLASTY.2.COMPRESSION SUTURES

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PREOPERATIVE EVALUATION PREOPERATIVE EVALUATION

Involves-Involves- 1)Screening, 1)Screening, 2)History taking, 2)History taking, 3)Preoperative examination & 3)Preoperative examination & 4)counselling4)counselling

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Systemic Contraindications-Systemic Contraindications-Diabetes mellitus ( if corneal sensation is Diabetes mellitus ( if corneal sensation is

not intact )not intact )Pregnancy/lactationPregnancy/lactationAutoimmune / connective tissue Autoimmune / connective tissue

disorders(RA,SLE,PAN etc)/ disorders(RA,SLE,PAN etc)/ ImmunodeficiencyImmunodeficiency

Abnormal wound healing-Marfans,Ehler-Abnormal wound healing-Marfans,Ehler-DanlosDanlos

-Keloids-KeloidsSystemic Infection-(HIV,TB)Systemic Infection-(HIV,TB)Drugs-Azathioprene,Steroids(Slow wound Drugs-Azathioprene,Steroids(Slow wound

healing)healing) -Antihypertensives, Antipsychotics,-Antihypertensives, Antipsychotics, Antiparkinsonian drugs (induce dry Antiparkinsonian drugs (induce dry

eye)eye)

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OPHTHALMIC OPHTHALMIC CONTRAINDICATIONSCONTRAINDICATIONS Disorders that may be exacerbated by Disorders that may be exacerbated by

PRKPRK - HZO (if active during last 6 months)- HZO (if active during last 6 months) - Glaucoma- Glaucoma Dry eye – Keratoconjunctivitis sicca, Dry eye – Keratoconjunctivitis sicca,

Exposure keratitis, Lid disordersExposure keratitis, Lid disorders Abnormal corneal shapeAbnormal corneal shape - Shape changes induced by contact lens- Shape changes induced by contact lens - High irregular astigmatism- High irregular astigmatism - Corneal ectasias : Keratoconus,- Corneal ectasias : Keratoconus, Keratoglobus, Pellucid marginal Keratoglobus, Pellucid marginal

degenerationdegeneration Uveitis, Lenticular changes, Progressive Uveitis, Lenticular changes, Progressive

retinal ds., myopic degeneration, retinal ds., myopic degeneration, Diabetic retinopathy, RP, RDDiabetic retinopathy, RP, RD

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OPHTHALMIC EXAMINATIONOPHTHALMIC EXAMINATION VISUAL ACUITYVISUAL ACUITY – Distance & Near : with & without – Distance & Near : with & without correctioncorrection REFRACTIONREFRACTION – Current spectacle correction – Current spectacle correction - Manifest refraction- Manifest refraction - Cycloplegic refraction (1% - Cycloplegic refraction (1%

cyclopentolate ) cyclopentolate ) EXTERNAL EXAMINATIONEXTERNAL EXAMINATION – Ocular dominance – Ocular dominance - Ocular motility- Ocular motility - Gross external - Gross external

examinationexamination SLIT-LAMP EXAMINATION SLIT-LAMP EXAMINATION – Fluorescein & vital – Fluorescein & vital

stainstain JONES’ BASAL TEAR SECRETION RATEJONES’ BASAL TEAR SECRETION RATE IOP MEASUREMENTIOP MEASUREMENT DILATED FUNDUSCOPYDILATED FUNDUSCOPY

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TOPOGRAPHIC ANALYSISTOPOGRAPHIC ANALYSIS1) Keratometry (measures 2) Computerized 1) Keratometry (measures 2) Computerized Videokeratography Videokeratography central 3 mm corneal curvature) (only way to central 3 mm corneal curvature) (only way to uncover early KC)uncover early KC)

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PACHYMETRYPACHYMETRY-- measuring thickness of cornea measuring thickness of cornea

1)1) ULTRASONIC ULTRASONIC PACHYMETRYPACHYMETRY

RecommendationRecommendations for minimum s for minimum bed thickness bed thickness (250µ) based (250µ) based upon ultrasonic upon ultrasonic devicesdevices

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2) ORBSCAN 2) ORBSCAN DEVICEDEVICE

- Optical deviceOptical device- Advantage – Advantage –

can provide can provide thickness thickness measurements measurements throughout the throughout the corneacornea

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EPIKERATOPHAKIAEPIKERATOPHAKIA

EPIKERATOPLASTY/ ONLAY LAMELLAR EPIKERATOPLASTY/ ONLAY LAMELLAR KERATOPLASTYKERATOPLASTY

Removal of epithelium from central Removal of epithelium from central cornea cornea peripheral annular keratotomy peripheral annular keratotomy lyophilized donor lenticule is lyophilized donor lenticule is reconstituted & sewn into the annular reconstituted & sewn into the annular keratotomy sitekeratotomy site

Adv.Adv.- simplicity & reversibility- simplicity & reversibility Disadv Disadv – irregular astigmatism, delayed – irregular astigmatism, delayed

visual recovery, prolonged epithelial visual recovery, prolonged epithelial defects.defects.

Abandoned procedure now.Abandoned procedure now.

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Radial Keratotomy (RK)Radial Keratotomy (RK) Series of 4-8 Series of 4-8

deep, radial deep, radial corneal stromal corneal stromal incisionsincisions

Weaken the Weaken the paracentral & paracentral & peripheral peripheral cornea & flatten cornea & flatten the central the central corneacornea

I/C- keratoconusI/C- keratoconus - -

astigmatismastigmatism - myopia- myopia

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LONG-TERM LONG-TERM COMPLICATIONSCOMPLICATIONS

- Bullous - Bullous keratopathy keratopathy secondary to secondary to endothelial cell endothelial cell lossloss

- Low stability of - Low stability of refractionrefraction

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Astigmatic Keratotomy (AK)Astigmatic Keratotomy (AK)

For astigmatism onlyFor astigmatism only 1-2 tranverse relaxing mid-1-2 tranverse relaxing mid-

peripheral corneal incisionsperipheral corneal incisions Arcuate or straight fashionArcuate or straight fashion Perpendicular to the steep meridianPerpendicular to the steep meridian Localized ectasia of peripheral Localized ectasia of peripheral

cornea & central flattening of the cornea & central flattening of the incised meridianincised meridian

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May be combined with LASIK, May be combined with LASIK, PRK, LASEK, Cataract PRK, LASEK, Cataract extraction.extraction.

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Cataract surgery - Limbal Relaxing Cataract surgery - Limbal Relaxing Incisions have gained popularity- more Incisions have gained popularity- more comfortable for patient than arcuate or comfortable for patient than arcuate or transverse mid-peripheral incisionstransverse mid-peripheral incisions

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PHOTOREFRACTIVE PHOTOREFRACTIVE KERATECTOMYKERATECTOMYFirst widely used procedure with First widely used procedure with the excimer laser (1987)the excimer laser (1987)

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PHOTOREFRACTIVE PHOTOREFRACTIVE KERATECTOMYKERATECTOMY

Outer layer of cornea is removed Outer layer of cornea is removed then laser is appliedthen laser is applied

vision improves as surface heals vision improves as surface heals after 4 to 7 daysafter 4 to 7 days

discomfort present during discomfort present during healinghealing

can cause corneal scarringcan cause corneal scarring

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PRK for MyopiaPRK for Myopia

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No microkeratome No microkeratome involvedinvolved

No flap createdNo flap created Ultimate visual Ultimate visual

results similar to results similar to LASIKLASIK

Longer recovery Longer recovery period (> 2 weeks)period (> 2 weeks)

Complications similar Complications similar to LASIK; Hazeto LASIK; Haze

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LASIK (Laser-assisted in situ LASIK (Laser-assisted in situ keratomileusis)keratomileusis)

Most commonly Most commonly performed refractive performed refractive surgerysurgery

Combines lamellar Combines lamellar corneal surgery with corneal surgery with accuracy of the excimer accuracy of the excimer laserlaser

Excimer laser ablation of Excimer laser ablation of corneal stroma beneath corneal stroma beneath a hinged corneal flap a hinged corneal flap that is created with a that is created with a mechanical femtosecond mechanical femtosecond laser microkeratomelaser microkeratome

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HISTORICAL REVIEWHISTORICAL REVIEW Barraquer first described lamellar refractive Barraquer first described lamellar refractive

surgery in 1949surgery in 1949 Dr. Ruiz introduced microtome propelled by Dr. Ruiz introduced microtome propelled by

gears & keratomiluesis in situ in early 1980sgears & keratomiluesis in situ in early 1980s Dr. Leo Bores performed 1Dr. Leo Bores performed 1stst keratomiluesis keratomiluesis

in situ in 1987 in the USin situ in 1987 in the US Burrato reported use of excimer laser in situ Burrato reported use of excimer laser in situ

after a cap of corneal tissue was removedafter a cap of corneal tissue was removed Pallikaris – idea of combining precision of Pallikaris – idea of combining precision of

excimer laser with lamellar corneal surgeryexcimer laser with lamellar corneal surgery LASIK was introduced & developed at the LASIK was introduced & developed at the

Univ. of Crete, GreeceUniv. of Crete, Greece Wavefront-guided LASIK became available Wavefront-guided LASIK became available

in the US in 2003in the US in 2003

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Types of lasers usedTypes of lasers used

Excimer : for corneal stromal Excimer : for corneal stromal ablationablation

Non-Excimer solid state lasers : Non-Excimer solid state lasers : for flap creationfor flap creation

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EXCIMER LASERSEXCIMER LASERSExcited dimer of two atoms Excited dimer of two atoms

-an inert gas(Argon)-an inert gas(Argon)

-a Halide(Fluoride)-a Halide(Fluoride) releases ultraviolet energy releases ultraviolet energy

at193nm at193nm Reshapes corneal surface by removing Reshapes corneal surface by removing

anterior stromal tissueanterior stromal tissue Process – Non-thermalProcess – Non-thermal

AblativeAblative

PhotodecompositionPhotodecomposition

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Laser delivery patterns :Laser delivery patterns : 1) 1) Broad-beam lasersBroad-beam lasers- deliver a large - deliver a large diameter beam of laser – starts small & diameter beam of laser – starts small & expands as the laser is deliveredexpands as the laser is delivered ADV.ADV. Less operative time Less operative time DISADV.DISADV. Creation of central islands Creation of central islands ( difficulty to maintain( difficulty to maintain uniform consistency over a larger diameter uniform consistency over a larger diameter beam)beam)

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2) Scanning excimer lasers:2) Scanning excimer lasers:

- Scanning-slit laser- Scanning-slit laser

- Flying spot laser- Flying spot laser

Provide smoother ablation than the Provide smoother ablation than the old broad-beam lasersold broad-beam lasers

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

of corneal collagen—less thermal and of corneal collagen—less thermal and collateral damagecollateral damage

Better pulse to pulse stabilityBetter pulse to pulse stabilityNot absorbed by air,water,tear fluid-Not absorbed by air,water,tear fluid-

so less sensitive to humidity or room so less sensitive to humidity or room temperaturetemperature

No purging with inert gases required.No purging with inert gases required.

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Patient selectionPatient selection

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

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

stable for at least 1 year.stable for at least 1 year. Current FDA approval-Current FDA approval-

Myopia-upto -15DMyopia-upto -15D Hyperopia –upto +6DHyperopia –upto +6D Astigmatism-upto 6DAstigmatism-upto 6D

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

Extreme keratometric values ( flatter Extreme keratometric values ( flatter than 41.00 or steeper than 47.00) than 41.00 or steeper than 47.00) avoidedavoided

Videokeratoghic clues to a KC suspect:Videokeratoghic clues to a KC suspect: K value > 47.2 D, K value > 47.2 D, Inferior steepening of > 1.4 D,Inferior steepening of > 1.4 D, difference of > 1.9 between K values of difference of > 1.9 between K values of

both eyesboth eyes Contact lens free period before Contact lens free period before

examination :examination : 3-4 wks for rigid contact lens wearers3-4 wks for rigid contact lens wearers 2 wks for soft contact lens wearers2 wks for soft contact lens wearers

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BASIC MECHANISMBASIC MECHANISM Normal cornea – prolate shape Normal cornea – prolate shape

( greater curvature centrally )( greater curvature centrally ) Myopic correctionMyopic correction – create an oblate – create an oblate

shape by central corneal laser shape by central corneal laser ablationablation

HyperopiaHyperopia- Excimer laser ablation at - Excimer laser ablation at mid-peripherymid-periphery steepening of central steepening of central corneacornea

Mixed astigmatismMixed astigmatism – – 1)Bitoric LASIK technique – flattening 1)Bitoric LASIK technique – flattening

the steep meridian with paracentral the steep meridian with paracentral ablation over the flat meridianablation over the flat meridian

2)Cross-cylinder technique – dividing 2)Cross-cylinder technique – dividing cylinder power into 2 symmetrical cylinder power into 2 symmetrical parts – half of the correction is parts – half of the correction is treated on the positive meridian & treated on the positive meridian & half on the negative meridianhalf on the negative meridian

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MUNNERLYN EQUATIONMUNNERLYN EQUATION

Roughly defines the depth of ablation Roughly defines the depth of ablation required to achieve a specific amount of required to achieve a specific amount of correctioncorrection

For 1 D correction For 1 D correction depth of ablation depth of ablation required (in microns) one-third of the required (in microns) one-third of the square of diameter (in mm)square of diameter (in mm)

So So each spherical equivalent dioptereach spherical equivalent diopter of of myopic correction performed at a myopic correction performed at a 6mm 6mm optical zoneoptical zone will ablate will ablate 12 microns12 microns of of tissuetissue

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OPERATIVE PROCEDUREOPERATIVE PROCEDURE 5mg Diazepam 5-10 min before procedure5mg Diazepam 5-10 min before procedure Verification of entered computer data Verification of entered computer data

before starting procedurebefore starting procedure Topical anasthesia-Proparacaine 0.5%, Topical anasthesia-Proparacaine 0.5%,

Lignocaine 4%.Lignocaine 4%. Surgical Painting and drapingSurgical Painting and draping Lid speculum with aspirationLid speculum with aspiration Proper centration over pupil & Proper centration over pupil &

maintenance by the aid of Tracking maintenance by the aid of Tracking systems & iris registrationsystems & iris registration

C/L eye taped shut to prevent cross-C/L eye taped shut to prevent cross-fixation & dryingfixation & drying

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Corneal marking Corneal marking with inkwith ink

Adequate Adequate placement of placement of suction ring suction ring using bimanual using bimanual techniquetechnique

Suction Suction engagement by engagement by foot controlfoot control

11stst step - Creation of flap step - Creation of flap

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Adequate IOP (>65mmHg) which is Adequate IOP (>65mmHg) which is necessary for the microkeratome to necessary for the microkeratome to create a pass and resect the create a pass and resect the corneal flap.corneal flap.

verified by BARRAQUER verified by BARRAQUER TONOMETERTONOMETER

confirmed by patient – temporary confirmed by patient – temporary loss of visualization of fixation lightloss of visualization of fixation light

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2nd step - Resection of 2nd step - Resection of corneal flapcorneal flap Artficial tear drops instilledArtficial tear drops instilled MICROKERATOMESMICROKERATOMES

1) Steel Microkeratome1) Steel Microkeratome-Uses Disposable blades-Uses Disposable blades-Blade Plate can be set at 120µ,140µ,160µ -Blade Plate can be set at 120µ,140µ,160µ

and180µ.and180µ.-Nasal or superiorly hinge flaps can be -Nasal or superiorly hinge flaps can be

created.created.-Eg.Hansatome,ACS,Carriazo Barraquer, Moria.-Eg.Hansatome,ACS,Carriazo Barraquer, Moria.

2) Waterjet Keratome2) Waterjet Keratome-Less debris & collateral damage than blade -Less debris & collateral damage than blade

keratomeskeratomes- Raised IOP not needed to create flap- Raised IOP not needed to create flap

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3) Laser Keratome (IntraLase)3) Laser Keratome (IntraLase)

- Solid-state laser- Solid-state laser - 1053 nm wavelength- 1053 nm wavelength - 3 µm spot size- high precision- 3 µm spot size- high precision - Uses brief - Uses brief Femtosecond laserFemtosecond laser pulses to pulses to

cause disruption in a lamellar planecause disruption in a lamellar plane - Needs lower vacuum & any hinge can be - Needs lower vacuum & any hinge can be

mademade - Can make flaps as thin as 100µ(Sub - Can make flaps as thin as 100µ(Sub

BowmansBowmans Keratomileusis)Keratomileusis)

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- Flap has vertical edges –so reduced - Flap has vertical edges –so reduced epithelial ingrowth.epithelial ingrowth.

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

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33rdrd Step-Delivery of Laser- Step-Delivery of Laser-After flap is lifted,assessment of residual corneal After flap is lifted,assessment of residual corneal

bed thickness usin USG pachymetrybed thickness usin USG pachymetry laser is applied to the stroma according to the laser is applied to the stroma according to the

ablation profile calculated by the machine.ablation profile calculated by the machine.Excimer Laser beam is delivered by the following Excimer Laser beam is delivered by the following

ways depending on the machine-ways depending on the machine-

Beam Delivery

Broad Beam Scanning Slit Beam Flying Spot

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

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44thth step-Reposition Of the step-Reposition Of the Flap-Flap-

After irrigating interface ,flap repositedAfter irrigating interface ,flap repositedSweeping movements with a wet cellulose Sweeping movements with a wet cellulose

sponge sponge From the hinge towards the periphery of From the hinge towards the periphery of

flapflapAdhesion verified – stretching the flap Adhesion verified – stretching the flap

towards gutter towards gutter Topical antibiotic, steroid & lubricant Topical antibiotic, steroid & lubricant

instillation instillation transparent plastic shields transparent plastic shields

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WAVEFRONT-GUIDED WAVEFRONT-GUIDED (CUSTOMIZED) EXCIMER LASER (CUSTOMIZED) EXCIMER LASER REFRACTIVE SURGERYREFRACTIVE SURGERY To correct higher-order aberrations in To correct higher-order aberrations in

addition to lower- order sphero-cylinder addition to lower- order sphero-cylinder correctionscorrections

- - LOWER ORDER LOWER ORDER NearsightednessNearsightedness FarsightednessFarsightedness AstigmatismAstigmatism -- HIGHER ORDER HIGHER ORDER Spherical aberration Spherical aberration Chromatic aberrationChromatic aberration DiffractionDiffraction Curvature of fieldCurvature of field ComaComa TrefoilsTrefoils QuadrifoilsQuadrifoils

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Higher order aberrations occur in Higher order aberrations occur in visually significant manner in 10-15% visually significant manner in 10-15% of populationof population

Cannot be corrected with Cannot be corrected with spherocylinder lens or conventional spherocylinder lens or conventional laser refractive surgerylaser refractive surgery

Correction – Hard contact lensesCorrection – Hard contact lenses

- Wavefront-guided - Wavefront-guided customizedcustomized

laser refractive surgerylaser refractive surgery

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MEASUREMENT OF WAVEFRONT MEASUREMENT OF WAVEFRONT ABERRATIONS (ABERROMETRY)ABERRATIONS (ABERROMETRY)

ABERROMETERABERROMETER

OUTGOING ABERROMETERSOUTGOING ABERROMETERS INGOING ABERROMETERSINGOING ABERROMETERS

Analyze outgoing light that emerges Analyze Analyze outgoing light that emerges Analyze ingoing light that forms aningoing light that forms an

From retina & passes through the image on From retina & passes through the image on the retinathe retina

Optical system of eye Optical system of eye Tscherning AberrometerTscherning Aberrometer

Hartmann-Shack Aberrometer Ray Hartmann-Shack Aberrometer Ray Tracing AberrometerTracing Aberrometer

(most commonly used) (most commonly used) Scanning Scanning Slit RefractometerSlit Refractometer

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ANALYSIS & DECOMPOSITION OF ANALYSIS & DECOMPOSITION OF WAVEFRONT ABERRATIONS INTO WAVEFRONT ABERRATIONS INTO

COMPONENTSCOMPONENTS

ANALYSIS OF ABERRATIONS

ZERNIKE POLYNOMIALS(most commonly used)

FOURIER ANALYSIS

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CUSTOMIZATION OF ABLATION CUSTOMIZATION OF ABLATION PROFILEPROFILE

TYPES OF CUSTOMIZATION

TOPOGRAPHY-GUIDED ABLATION(Conventional laser surgery)

WAVEFRONT-GUIDED ABLATION(Customized laser surgery)

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Conversion of wavefront Conversion of wavefront measurement data to an ablation measurement data to an ablation profile profile

Imported to an excimer laser Imported to an excimer laser

Precise registration of these Precise registration of these patterns on cornea by patterns on cornea by eye trcking eye trcking & iris registration technology& iris registration technology

Precise wavefront-guided ablation Precise wavefront-guided ablation during LASIK is achievedduring LASIK is achieved

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CUSTOMIZED ABLATION CUSTOMIZED ABLATION PLATFORMSPLATFORMS1) Nidek Advanced 1) Nidek Advanced

VisionVision EXcimer Laser EXcimer Laser

systemsystem OPD-Scan optical path OPD-Scan optical path

difference scanning difference scanning system (combines system (combines measurement of measurement of corneal topography & corneal topography & aberrometry)aberrometry)

Develops customized Develops customized ablation profileablation profile

EC-5000CX II excimer EC-5000CX II excimer laser delivers ttlaser delivers tt

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2) VISX S4 2) VISX S4 CustomVue CustomVue Platform (Santa Platform (Santa Clara, CA)Clara, CA)

Wavescan Wavescan wavefront system wavefront system – Hartmann-Shack – Hartmann-Shack wavefront sensorwavefront sensor

STAR S4 excimer STAR S4 excimer laser sytem laser sytem delivers delivers customized laser customized laser ablationablation

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3) Alcon Customized Cornea Platform

LADARWave wavefront sensor ( a Hartmann-Shack eberrometer)

LADARVision system to deliver customized laser ablation

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4)Bausch and Lomb 4)Bausch and Lomb Zyoptix SystemZyoptix System

Diagnostic part :Diagnostic part :

- Zywave aberrometer - Zywave aberrometer – a Hartmann-Shack – a Hartmann-Shack sensorsensor

- ORBSCAN – 3D - ORBSCAN – 3D information about information about corneacornea

Truncated Gaussian Truncated Gaussian beam laser – 2 sizes –beam laser – 2 sizes –

2mm – corrects 2mm – corrects majority of refractive majority of refractive error in short timeerror in short time

1mm – more specific 1mm – more specific ablation pattern on ablation pattern on transition zonestransition zones

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5) Allegretto 5) Allegretto Wavefront-Guided Wavefront-Guided AblationAblation

Allegretto wave Allegretto wave analyzer – analyzer – Tscherning Tscherning AberrometerAberrometer

Allegretto excimer Allegretto excimer laser system – high laser system – high repetition rate spot repetition rate spot laser (200Hz) with a laser (200Hz) with a small Gaussian small Gaussian beam sizebeam size

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COMPLICATIONSCOMPLICATIONSINTRAOPERATIVE INTRAOPERATIVE

COMPLICATIONSCOMPLICATIONS

1) 1) Incomplete flap Incomplete flap – – premature termination of microkeratome premature termination of microkeratome

advancementadvancement - inadequate globe exposure- inadequate globe exposure - loss of suction during pass- loss of suction during pass Never reverse microtome & then go Never reverse microtome & then go

forwardforwardpenetration to a deeper level than initial penetration to a deeper level than initial

passpass

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2) 2) Thin flapThin flap

- due to poor suction- due to poor suction

- difficult to - difficult to reposition & likely reposition & likely to wrinkleto wrinkle

3) 3) Buttonholed flapButtonholed flap

- If K > 50 D- If K > 50 D

- Ablation should not - Ablation should not be performed, flap be performed, flap repositionedrepositioned

4) 4) Full thickness Full thickness resectionresection

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5) 5) Free capFree cap – flat/ – flat/ small cornea, poor small cornea, poor suctionsuction

- Small / decentered : - Small / decentered : procedure abortedprocedure aborted

- Adequate size/ well - Adequate size/ well centered : placed on centered : placed on conjunctiva with conjunctiva with epithelial side down epithelial side down & procedure & procedure completedcompleted

6) 6) Epithelial defectsEpithelial defects – – prevented by prevented by adequate lubricationadequate lubrication

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ABLATION COMPLICATIONSABLATION COMPLICATIONS1) 1) Central islandsCentral islands – small central elevations – small central elevations

a) abnormal beam profile (broad beam lasers)a) abnormal beam profile (broad beam lasers)

b) particulate matter blocking subsequent b) particulate matter blocking subsequent laser pulseslaser pulses

c) increased hydrationc) increased hydration

2) 2) DecentrationDecentration – current lasres with – current lasres with incorporated eye-tracking & iris registration incorporated eye-tracking & iris registration systemssystems

3)3) Under/ Over-correction Under/ Over-correction

- excessive hydration : undercorrection- excessive hydration : undercorrection

- desiccation : overcorrection & haze- desiccation : overcorrection & haze

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POSTOPERATIVE POSTOPERATIVE COMPLICATIONSCOMPLICATIONS1)1) Interface debris Interface debris – mostly meibomian gland – mostly meibomian gland

material – cleaning of interface with BSSmaterial – cleaning of interface with BSS

2) 2) Flap displacementFlap displacement – first 24 hrs – first 24 hrs - lifted & repositioned- lifted & repositioned

3) 3) Night vision disturbancesNight vision disturbances – haloes / glare – haloes / glare

4)4)Post Lasik Dry eyePost Lasik Dry eye-- Fluctuating vision,SPKFluctuating vision,SPK Temporary neuropathic corneaTemporary neuropathic cornea Confocal microscopy-90% reduction in Confocal microscopy-90% reduction in

corneal nerve fibres-regeneration by 1 corneal nerve fibres-regeneration by 1 year.year.

Rx-Preservative Free lubricantsRx-Preservative Free lubricants

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6) 6) Diffuse lamellar Diffuse lamellar keratitis (Sands of keratitis (Sands of Sahara syn)Sahara syn)

- non-infective - non-infective interface interface inflammationinflammation

- 1- 1stst week after LASIK week after LASIK

- fine granular sand-like - fine granular sand-like infiltrate in the infiltrate in the interface peripheryinterface periphery

- if not treated- if not treated corneal scarringcorneal scarring

- tt topical steroids- tt topical steroids

5)5)Punctate epithelial keratopathyPunctate epithelial keratopathy – pre- – pre-existing dry eye / blepharitisexisting dry eye / blepharitis

- tt frequent lubrication , punctal plugs- tt frequent lubrication , punctal plugs

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Grade 1-Grade 1-

Focal involvement Focal involvement

- Normal V/A.- Normal V/A.

- Rx Intensive topical - Rx Intensive topical steroids.steroids.

Grade IIGrade II – –

Diffuse involvement Diffuse involvement

– – Normal V/A.Normal V/A.

- Rx-Add systemic - Rx-Add systemic steroids.steroids.

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Grade IIIGrade III – – Diffuse confluent Diffuse confluent

granular depositsgranular deposits - Reduced V/A.No AC - Reduced V/A.No AC

reaction.reaction. - Rx-Same as - Rx-Same as

above+Antibioticsabove+Antibiotics

Grade IVGrade IV – – Diffuse confluent Diffuse confluent

granular deposits granular deposits +intense central +intense central striae.striae.

- Marked Reduced V/A- Marked Reduced V/A - Rx-Interface - Rx-Interface

irrigation + aboveirrigation + above

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CausesCauses-Proposed Theory-Proposed Theory Bacterial cell wall endotoxinBacterial cell wall endotoxin Cleaning solution toxicity Cleaning solution toxicity Talc from glovesTalc from gloves Miebomian secretionsMiebomian secretions

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7) 7) Flap striae & microstriaeFlap striae & microstriaeFlap undulationsFlap undulationsMacrostriaeMacrostriae-Linear-Linearlines in lines in

clusters,seenclusters,seenon retroillumination on retroillumination Causes-IncorrectCauses-Incorrectposition of flap position of flap

-Movement of -Movement of flap after LASIKflap after LASIK

Rx-Lift flapRx-Lift flap-Rehydrate and -Rehydrate and

float it backfloat it back -Check for flap -Check for flap

adhesionadhesion

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MicrostriaeMicrostriae-Flap in -Flap in position but fine position but fine wrinkles seen wrinkles seen superficiallysuperficially

-Due to large -Due to large myopic ablationmyopic ablation

-Rx- Observe.They -Rx- Observe.They resolve resolve spontaneouslyspontaneously

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8) 8) Epithelial ingrowthEpithelial ingrowth Presents 1-3 Presents 1-3

months after LASIK.months after LASIK. Causes-Epithelial Causes-Epithelial

cells trapped under cells trapped under flapflap

Risk factorsRisk factors -Peripheral -Peripheral

epithelial defectepithelial defect -Poor flap adhesion-Poor flap adhesion -Buttonholed flaps-Buttonholed flaps -Repeat LASIK-Repeat LASIK

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

GRADE 2-Opaque cells <2mm from flap GRADE 2-Opaque cells <2mm from flap edge with rolled flap edgeedge with rolled flap edge

GRADE 3-Grey to white fine opaque line GRADE 3-Grey to white fine opaque line extending >2mm from flap edge.extending >2mm from flap edge.

GRADE 4-If ingrowth >2mm from edge GRADE 4-If ingrowth >2mm from edge with documented progressionwith documented progression

RxRx flap lifted flap lifted epithelium scraped at epithelium scraped at stroma & under flapstroma & under flap repositioned. repositioned. Mitomycin-C can be usedMitomycin-C can be used

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9) 9) Infectious keratitisInfectious keratitis – vision – vision threateningthreatening

- M/C organisms – Atypical - M/C organisms – Atypical mycobacteria, Staphylococcimycobacteria, Staphylococci

- Prevention – prophylactic antibiotics- Prevention – prophylactic antibiotics

- Pre-treatment of - Pre-treatment of meibomian gl. diseasemeibomian gl. disease

- sterile instruments & - sterile instruments & techniquestechniques

- suction lid specula- suction lid specula

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10) 10) KeractasiaKeractasia - Ablation beyond 250 µm of posterior corneal - Ablation beyond 250 µm of posterior corneal

stromastroma - LASIK performed on unrecognized KC - LASIK performed on unrecognized KC

suspectssuspects - tt – RGP lenses, corneal transplant- tt – RGP lenses, corneal transplant

11)11) Post op Glaucoma(Pseudo DLK) Post op Glaucoma(Pseudo DLK)-Steroid -Steroid induced.induced.

12)12) Vitreoretinal Complications- Vitreoretinal Complications- Increased risk of RD due to alteration of Increased risk of RD due to alteration of

anterior vitreous by suction ring-Risk anterior vitreous by suction ring-Risk 0.08%.0.08%.

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

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LASEK & Epi-LASIKLASEK & Epi-LASIK

Corneal surface ablative refractive Corneal surface ablative refractive proceduresprocedures

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

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

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

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LASEKLASEK

Creating an epithelial flap with Creating an epithelial flap with dilute alcohol (18%) applied for dilute alcohol (18%) applied for 25-35 seconds & repositioning 25-35 seconds & repositioning this flap after laser ablationthis flap after laser ablation

Plane of cleavage Plane of cleavage Hemidesmosomal attachments in Hemidesmosomal attachments in the most superficial part of the most superficial part of lamina lucida of BMlamina lucida of BM

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Epi-LASIKEpi-LASIK

Use of a motorized epithelial Use of a motorized epithelial separator with oscillating blade, to separator with oscillating blade, to mechanically separate a 60-80µ mechanically separate a 60-80µ corneal epithelial flap from stroma & corneal epithelial flap from stroma & repositioning this flap after laser repositioning this flap after laser ablationablation

Plane of cleavage Plane of cleavage Not within but Not within but underneath the Basement Membraneunderneath the Basement Membrane

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HISTORYHISTORY

11stst LASEK 1996 by Dr. Azar LASEK 1996 by Dr. Azar Cimberle & Camellin Cimberle & Camellin

independently coined the term independently coined the term LASEKLASEK

Epi-LASIK a recent development Epi-LASIK a recent development in refractive surgery technology in refractive surgery technology

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ADVANTAGES OVER PRKADVANTAGES OVER PRK

Greater post-operative comfortGreater post-operative comfort Faster visual recoveryFaster visual recovery allows allows

bilateral simultaneous surgerybilateral simultaneous surgery Reduced risk of corneal hazeReduced risk of corneal haze

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ADVANTAGES OVER LASIKADVANTAGES OVER LASIK

Flap related complications are Flap related complications are eliminated in LASEKeliminated in LASEK

If microkeratome related If microkeratome related complications occur during Epi-complications occur during Epi-LASIK, procedure can be easily LASIK, procedure can be easily converted to PRK & completedconverted to PRK & completed

Absence of corneal Absence of corneal lamellar lamellar flap flap in both procedures, reduces risk in both procedures, reduces risk of keractasiaof keractasia

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COMPLICATIONSCOMPLICATIONS

INTRAOPERATIVEINTRAOPERATIVE

LASEK relatedLASEK related Epi-LASIK relatedEpi-LASIK related

1) Alcohol leakage Flap-related 1) Alcohol leakage Flap-related problems:problems:

during surgery - free flapduring surgery - free flap

2) Incomplete - incomplete 2) Incomplete - incomplete flapflap

epithelial detachment - buttonholingepithelial detachment - buttonholing

(insufficient alcohol(insufficient alcohol

exposure)exposure)

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EARLY POST-OP COMPLICATIONSEARLY POST-OP COMPLICATIONS

Delayed epithelial healing (3-5 days)Delayed epithelial healing (3-5 days) Pain – resolution of pain Pain – resolution of pain

accompanies epithelial closureaccompanies epithelial closure Infiltrates & InfectionInfiltrates & Infection

- Sterile infiltrates: alcohol- - Sterile infiltrates: alcohol- predisposing factorpredisposing factor

Dry eyeDry eye Corneal haze – with increased Corneal haze – with increased

ablation depthsablation depths

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Laser Thermo-Laser Thermo-Keratoplasty (LTK)Keratoplasty (LTK) FDA approval Jan 2000FDA approval Jan 2000 Ho:YAG (Holmium:yttrium-aluminium-Ho:YAG (Holmium:yttrium-aluminium-

garnet) laser – deliver laser energy to garnet) laser – deliver laser energy to periphery of corneaperiphery of cornea

For Hyperopia (0.75 to 2.5 D)For Hyperopia (0.75 to 2.5 D) Takes months to stabilizeTakes months to stabilize In time, the effect wears off in a In time, the effect wears off in a

substantial number of casessubstantial number of cases

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Laser Thermal Keratoplasty Laser Thermal Keratoplasty (LTK)(LTK)

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CONDUCTIVE CONDUCTIVE KERATOPLASTYKERATOPLASTY Application of low-energy, high Application of low-energy, high

frequency radiofrequency current to frequency radiofrequency current to heat & shrink peripheral & paracentral heat & shrink peripheral & paracentral stromal collagenstromal collagen resulting in resulting in steepening of central corneasteepening of central cornea

Used for hyperopia (1 – 2.25D), Used for hyperopia (1 – 2.25D), hyperopic astigmatism and presbyopiahyperopic astigmatism and presbyopia

FDA approved 2002FDA approved 2002 Provides better stability than the Provides better stability than the

previously used procedure Laser previously used procedure Laser Thermal Keratoplasty (LTK)Thermal Keratoplasty (LTK)

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CORNEAL RESPONSE TO HEATCORNEAL RESPONSE TO HEAT

55 – 58 ˚C 55 – 58 ˚C collagen shrinkage collagen shrinkage (disruption of (disruption of

H bonds of tertiary H bonds of tertiary collagen structure)collagen structure)

65 – 78 ˚C65 – 78 ˚C collagen relaxation collagen relaxation

> 78 ˚C > 78 ˚C collagen necrosis collagen necrosis

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HyperopiaHyperopia

Lower corrections : 8 spots at 6mm optical Lower corrections : 8 spots at 6mm optical zonezone

& 8 spots at 7mm optical & 8 spots at 7mm optical zonezone

Greater corrections : 24 spots applied ( 8 Greater corrections : 24 spots applied ( 8 additionaladditional

(+2 to +2.50D ) spots at 8mm optical (+2 to +2.50D ) spots at 8mm optical zone)zone)

Even greater corrections : 32 spotsEven greater corrections : 32 spots Hyperopic astigmatismHyperopic astigmatism

Peripheral heat spots along a single Peripheral heat spots along a single (flatter) meridian(flatter) meridian

Effect decreases with time : production of Effect decreases with time : production of new collagen by corneal fibroblastsnew collagen by corneal fibroblasts

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Conductive Keratoplasty Conductive Keratoplasty (CK)(CK)

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SCLERAL EXPANSION SCLERAL EXPANSION BANDSBANDS Designed to treat Designed to treat

presbyopiapresbyopia Not FDA approvedNot FDA approved Theory: Theory:

Presbyopia is due Presbyopia is due to slackening of to slackening of fibers attached to fibers attached to the lens.the lens.

Figure : Implanted scleral expansion band (full circular band model)

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Intrastromal Corneal Ring Intrastromal Corneal Ring SegmentsSegments(Intacs) (Intacs) PMMA arcuate segments placed PMMA arcuate segments placed

within peripheral cornea to correct within peripheral cornea to correct myopiamyopia

FDA Approved 1999FDA Approved 1999 << 3.0 D myopia , 3.0 D myopia , << 1.0D 1.0D

AstigmatismAstigmatism Emerging role as an adjunct for Emerging role as an adjunct for

keratoconus & corneal ectasiakeratoconus & corneal ectasia

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11stst generation ICRS : 360˚ ICRS generation ICRS : 360˚ ICRS

Current design: 2 PMMA Current design: 2 PMMA segments,150˚ arc lengthsegments,150˚ arc length

Hexagonal cross sectionHexagonal cross section

Fixed inner diam. 6.8 mmFixed inner diam. 6.8 mm

Fixed outer diam. 8.1 mmFixed outer diam. 8.1 mm

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Refractive effect directly Refractive effect directly related to thicknessrelated to thickness

INTACS INTACS THICKNESS THICKNESS (mm)(mm)

RECOMMENDED RECOMMENDED PRESCRIBING RANGE (D)PRESCRIBING RANGE (D)

0.25 -1.00 to -1.63

0.30 -1.75 to -2.25

0.35 -2.38 to -3.00

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SURGICAL TECHNIQUESURGICAL TECHNIQUE ICRS channel ICRS channel

formation at 2/3formation at 2/3rdrd corneal depth, corneal depth, outside central outside central optical zoneoptical zone

Insertion of segmentInsertion of segment Suturing of entry Suturing of entry

sitesite AdvAdv ReversibilityReversibility HyperacuittyHyperacuitty Maintenance of Maintenance of

corneal asphericitycorneal asphericity

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PHAKIC INTRAOCULAR PHAKIC INTRAOCULAR LENSESLENSES Artificial lenses implanted in the Artificial lenses implanted in the

anterior or posterior chamber in the anterior or posterior chamber in the presence of the natural crystalline presence of the natural crystalline lens to correct refractive errorslens to correct refractive errors

Intraoperative iridectomy or Intraoperative iridectomy or preoperative Nd:YAG laser preoperative Nd:YAG laser iridotomies – necessary to avoid post-iridotomies – necessary to avoid post-op pupillary block glaucomaop pupillary block glaucoma

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3 types3 types

Anterior chamber-angle supported PIOLAnterior chamber-angle supported PIOL

AC iris-fixatedAC iris-fixated

Posterior chamber PIOLPosterior chamber PIOL

Early models – PMMAEarly models – PMMA Newer models – foldable (more safe & Newer models – foldable (more safe &

efficacious)efficacious)

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AC angle-AC angle-supportedsupported

AC iris-AC iris-fixatedfixated

PC sulcus-PC sulcus-supportedsupported

NuVita NuVita (Bausch & (Bausch &

Lomb)Lomb)

Verisyse/ Verisyse/ Artisan Artisan

(AMO/Op(AMO/Ophtec)htec)

Implantable Implantable Contact Lens Contact Lens

(ICL)(ICL)

Vivarte (Ciba Vivarte (Ciba vision)vision)

Artiflex/ Artiflex/ VeriflexVeriflex

Phakic Phakic Refractive Refractive Lens (PRL)Lens (PRL)

Kelman DuetKelman Duet SticklensSticklens

I-CAREI-CARE

Acrysof ACAcrysof AC

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GENERAL CRITERIA FOR GENERAL CRITERIA FOR IMPLANTING PHAKIC IOLsIMPLANTING PHAKIC IOLs Age above 18 yearsAge above 18 years Stable refraction (< 0.5D change for 6 Stable refraction (< 0.5D change for 6

months)months) Ammetropia not suitable for Excimer laser Ammetropia not suitable for Excimer laser

surgery (high powers or thin cornea)surgery (high powers or thin cornea) AC depth >= 3.2mm for iris-claw lensAC depth >= 3.2mm for iris-claw lens >= 2.5mm for pc PIOLs>= 2.5mm for pc PIOLs Minimum endothelial cell density Minimum endothelial cell density > 3500 cells/mm² at 21 yrs age> 3500 cells/mm² at 21 yrs age > 2800 cells/mm² at 31 yrs age > 2800 cells/mm² at 31 yrs age > 2200 cells/mm² at 41 yrs age> 2200 cells/mm² at 41 yrs age > 2000 cells/mm² at 45 yrs age> 2000 cells/mm² at 45 yrs age No other ocular pathology (corneal No other ocular pathology (corneal

disorders, glaucoma, uveitis, cataract)disorders, glaucoma, uveitis, cataract)

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IndicationsIndications High MyopiaHigh Myopia December 2004, FDA approved 1December 2004, FDA approved 1stst PIOL : PIOL : Verisyse/ Artisan ‘iris-claw’ lensVerisyse/ Artisan ‘iris-claw’ lens Myopia -5 to -20 DMyopia -5 to -20 D Astigmatism upto 2.5 DAstigmatism upto 2.5 D December 2005, FDA approved a 2December 2005, FDA approved a 2ndnd PIOL : PIOL : Visian ICL(Implantable Contact Lens)Visian ICL(Implantable Contact Lens) Myopia -3 to -20 DMyopia -3 to -20 D Astigmatism upto 2.5 DAstigmatism upto 2.5 D

High HyperopiaHigh Hyperopia Upto +3.0 DUpto +3.0 D

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IOL power calculationIOL power calculationAC PIOL AC PIOL - Power calculation is independent of Power calculation is independent of

axial length of eyeaxial length of eye- Depends on : 1)Central corneal Depends on : 1)Central corneal

curvature-curvature- keratometry (k)keratometry (k) 2) ACD2) ACD 3) Preoperative spherical 3) Preoperative spherical

equivalentequivalent

PC PIOLPC PIOL- Corneal thickness & axial length also - Corneal thickness & axial length also

taken into considerationtaken into consideration

Ancillary testsAncillary tests

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AC DIMENSIONS & SIZING OF AC DIMENSIONS & SIZING OF PIOLPIOL Most of the complications arise due to Most of the complications arise due to

inaccurate sizin of PIOLsinaccurate sizin of PIOLs External measurement from limbus-to-External measurement from limbus-to-

limbus( white-to-white dist.)limbus( white-to-white dist.) Gives approx estimation of AC Gives approx estimation of AC

diameterdiameter

- Measured b/w 3 & 9 o’clock meridians - Measured b/w 3 & 9 o’clock meridians with caliperswith calipers

- ORBSCAN- ORBSCAN

- Videokeratoscopes- Videokeratoscopes

- High frequency UBM- High frequency UBM

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Diam of lens = w-w dist + 0.5 to Diam of lens = w-w dist + 0.5 to 1.0 mm1.0 mm (For both angle & sulcus- (For both angle & sulcus-supported PIOLs)supported PIOLs)

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AC angle-supported AC angle-supported PIOLsPIOLs

NuVitaNuVita

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VivarteVivarte

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AC iris-fixated PIOLsAC iris-fixated PIOLsArtisan/ VerisyseArtisan/ Verisyse

Most commonly used phakic IOLMost commonly used phakic IOL

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Artiflex/ VeriflexArtiflex/ Veriflex

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PC sulcus-supported PC sulcus-supported PIOLPIOL

Implantable Contact Lens (ICL)Implantable Contact Lens (ICL)

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ADVANTAGESADVANTAGES

Most stable & predictable refractive Most stable & predictable refractive methodmethod

Newer designs – improved safety & Newer designs – improved safety & efficacyefficacy

ReversibleReversible Significant gain of postoperative BCVA in Significant gain of postoperative BCVA in

myopia – reduction in image minificationmyopia – reduction in image minification No loss of contrast sensitivity (as seen in No loss of contrast sensitivity (as seen in

LASIK)LASIK)

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COMPLICATIONSCOMPLICATIONS

Haloes & glare Pupillary ovalization ( Angle supported PIOLs) Endothelial damage Elevation of IOP Uveits (iris trauma during surgery) Cataract (mostly nuclear)

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COMPLICATIONSCOMPLICATIONS

Anterior chamber inflammation/ Anterior chamber inflammation/ pigment dispersion – repeated pigment dispersion – repeated traumatic attempts at iris traumatic attempts at iris enclavation (Iris-fixated PIOLs)enclavation (Iris-fixated PIOLs)

Iris atrophy & IOL dislocation Iris atrophy & IOL dislocation (Iris-fixated PIOLs)(Iris-fixated PIOLs)

Hyphaema (Iris-fixated PIOLs)Hyphaema (Iris-fixated PIOLs) Decentration / Dislocation into Decentration / Dislocation into

vitreous cavity (PC PIOLs)vitreous cavity (PC PIOLs)

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BIOPTICSBIOPTICS Concept of first implanting a phakic Concept of first implanting a phakic

IOL to reduce the amount of IOL to reduce the amount of myopia, then fine tuning the myopia, then fine tuning the residual correction with LASIKresidual correction with LASIK

I/Cs –extremely high myopiaI/Cs –extremely high myopia

- high astigmatism- high astigmatism

- lens power not available- lens power not available Combination has expanded the Combination has expanded the

limits of refractive surgerylimits of refractive surgery

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