Dr.Subhadri Manna

PGT,CNMC&H

WHY OPT FOR REFRACTIVE

SURGERY??Surgery to correct refractive errors.

PREVIOUSLY

• vocation

• sport

• spex/C/L intolerance

NOW

• cosmesis

• frustration with use of spex and C/L

• Improved unaided VA

A. keratorefractive

procedures

1.Incisional refractive techniques

Radial keratotomy

Astigmatic keratotomy(AK)

Hexagonal keratotomy

Limbal relaxing incision(LRI)

Opposite clear corneal incision(OCCI)

2.Lamellar corneal refractive

procedures

Freeze keratomileusis

Epikeratophakia

Non freeze keratomileusis

keratomileusis in situ

Automated lamellar keratoplasty(ALK)

Small incision lenticule extraction

corneoplastique

3.Laser ablation corneal

procedures

PRK

Laser subepithelial

keratomileusis(Lasek)

LASIK

E-LASIK

C-LASIK

4.Corneal shrinkage refractive

procedure

Thermal laser keratoplasty(TLK)

Conductive keratoplasty(CK)

CLASSIFICATION OF REFRACTIVE

PROCEDURES

5.Corneal implants

Intracorneal contact lenses(ICL)

Intrastromal corneal ring

segments(Intacs)

6.Corneal tissue moulding

Orthokeratology

B. Lens-based

refractive proceduresPhakic refractive lenses(PRL)

Refractive lens exchange(RLE)

c. Combined lens and

corneal refractive

proceduresBioptics

Trioptics

PREOPERATIVE EVALUATION

Involves-

• Screening,

• History taking

• Preoperative examination & counselling

OPHTHALMIC EXAMINATION

• VISUAL ACUITY – Distance & Near : with & without correction

• REFRACTION – Current spectacle correction

- Manifest refraction

- Cycloplegic refraction (1% cyclopentolate )

• EXTERNAL EXAMINATION

- Ocular motility

- Gross external examination

• SLIT-LAMP EXAMINATION – Fluorescein & vital stain

• JONES’ BASAL TEAR SECRETION RATE

TOPOGRAPHIC ANALYSIS

• Keratometry (measures central 3 mm corneal curvature)

• Computerized Videokeratography (only way to uncover early KC)

PACHYMETRY

• measuring thickness of cornea.

ORBSCAN DEVICE

• Optical device

• Advantage – can provide thickness measurements throughout the

cornea.

Systemic Contraindications

• Diabetes mellitus ( if corneal sensation is not intact )

• Pregnancy/lactation

• Autoimmune / connective tissue

• disorders(RA,SLE,PAN etc)

• Immunodeficiency

• Abnormal wound healing-Marfans,Ehler-Danlos,Keloids

• Systemic Infection-(HIV,TB)

• Drugs-Azathioprene,Steroids(Slow wound healing)

• Antihypertensives

• Antipsychotics

OPHTHALMIC

CONTRAINDICATIONS• Disorders that may be exacerbated by PRK

- HZO (if active during last 6 months)

- Glaucoma

• Dry eye – Keratoconjunctivitis sicca,Exposure keratitis, Lid disorders

• Abnormal corneal shape

- Shape changes induced by contact lens

- High irregular astigmatism

- Corneal ectasias : Keratoconus,Keratoglobus, Pellucid marginal

degeneration

• Uveitis, Lenticular changes, Progressive retinal ds., myopic

degeneration, Diabetic retinopathy, RP, RD

Radial keratotomy

Svyatoslav Fyodorov, a Russian national, is accredited with the

development of modern radial keratotomy (RK).

Procedure

• Involves radial cuts on epithelial side of cornea to stroma with diamond knife.

• Pattern = spokes of a bicycle wheel

• Extra-pupillary region

• Principle : incisions => side of cornea to bulge => central corneal flattening => reduction in myopia

Procedure

• The length of the knife blade and the associated depth of the

incisions were set based on the corneal thickness, which was

usually measured with an ultrasonic pachymeter.

• The ideal depth of RK incisions was 85%-90% of the corneal

thickness.

Indications

• RK is suitable for patients with upto moderate myopia (-1D to

-4D).

• Treatment of higher degree of myopia often requires more than

8 incisions and longer incisions with smaller optical zones .

Complications

• Diurnal fluctuations: The cornea gradually steepens during the

waking hours.

• Under correction and overcorrection

• Increased astigmatism

• Instability of refractive correction with hyperopic shift

• Perforation of the cornea

• traumatic globe rupture

• bacterial keratitis

Complications

• Starburst pattern and glare:

Due to scattering of light from the radial incisions or scars. More

commonly in patients with smaller clear optical zones.

Contraindication

Who have job of night driving (glare)

Sports persons & security personals (traumatic globe perforation)

Astigmatic Keratotomy (AK)

• For astigmatism only

• 1-2 tranverse relaxing mid-peripheral corneal incisions

• Arcuate or straight fashion

• Perpendicular to the steep meridian

• Localized ectasia of peripheral cornea & central flattening of the

incised meridian

• May be combined with

LASIK, PRK,LASEK,

Cataract extraction.

Laser used RS

• Excimer laser(ArF) - 193nm

• Solid state diode laser -680nm

• Femtosecond laser(Nd:glass) -1053nm

Excimer laser

• Acronym EXCIMER= “excited

dimer”

• Dimer of inert gas eg. Argon or

Xenon bound with a halogen eg.

Fluorine or Chloride

• combination=diatomic gas halide -

temporary excited state

• during decay => emits UV of 193nm

=> removal of controlled amts of

tissue with extreme precision

• Act s by photodisruption

• Use corneal ablation in RS

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.

Photoablation

Cornea extremely high absorption

coefficient at 193nm

Photon has sufficient energy to break carbon–carbon and carbon–

nitrogen bonds of peptide in corneal collagen molecule

Collagen polymer ruptures into small fragments and a discrete

volume of corneal tissue is removed

• ablation per pulse is dependent on the radiant exposure, typically

within the range of 0.1–0.5μm per pulse at a radiant exposure of

50–250mJ/cm2.14,15

The Femtosecond Laser

• Infra red wave (1053nm)

• Each pulse of focused laser light lasts approximately 10-15

seconds (500-800 femtoseconds).

• High power as pulse time very short

• Penetration power is more wave length more

PHOTOREFRACTIVE

KERATECTOMY

• First widely used procedure with the excimer laser

(1987)

PHOTOREFRACTIVE

KERATECTOMY

• Outer layer of cornea is removed then laser is applied

• vision improves as surface heals after 4 to 7 days

• discomfort present during healing

• can cause corneal scarring

Photorefractive keratectomy (PRK)

• Photorefractive keratectomy (PRK) is a procedure in which the

cornea is reshaped using an excimer laser.

• PRK involves epithelial removal and photoablation of

Bowman’s layer and anterior corneal stromal tissue

• surgical treatment of myopia, hyperopia, and astigmatism

Procedure

• Anesthesia

• Removal of corneal epithelium

• Pt. asked to fixed to aiming beam laser

• Laser(Nd-YAG or Excimer or Nd-YLF Pico second) apply to

ablate bowman and superficial stromal layer

• patching

• Mitomycin C (0.02%) some time applied for 90 secs

Post op. care

• 24 hrs patching

• Cycloplegic

• Steroid

• Topical steroid

• Tear drop

• BCL

Complications

• Pain

• Decentration of ablation zone

• Corneal haze

• Night glare and halo

• Delayed epithelial healing

• Central island

• Corneal ulser

• Diminished corneal sensation

• Increase IOP

• Sub retinal hemorrhage.

LASIK(Laser in situ Keratomileusis )

• LASIK or Laser in situ Keratomileusis reshapes the cornea using

laser beam.

• Introduced by Barraquer in 1949.

• Corrects vision by altering refractive power of the eye by

calculated change in the corneal curvature.

• Used to treat low to high refractive errors including astigmatism.

HISTORICAL REVIEW

• Barraquer first described lamellar refractive surgery in 1949

• Dr. Ruiz introduced microtome propelled by gears & keratomiluesis

in situ in early 1980s

• Dr. Leo Bores performed 1st keratomiluesis in situ in 1987 in the

US

• Burrato reported use of excimer laser in situ after a cap of corneal

tissue was removed

• Pallikaris – idea of combining precision of excimer laser with

lamellar corneal surgery

• LASIK was introduced & developed at the Univ. of Crete, Greece

• Wavefront-guided LASIK became available in the US in 2003

PATIENT SELECTION

• Above 18 years of age.

• Stable refractive error at least 1year.

• Healthy cornea.

• Contraindicated in inadequate corneal thickness (<450

μ), keratoconus, other corneal diseases, pregnancy,

lactation and certain medical conditions.

• Contact lens wearers to discontinue lenses for a few

days prior to examination and surgery.

EXAMINATION

• Visual acuity

• S/L examination

• IOP

• Measurement of pupil size(OZ>pupil size)

• Corneal topography.

• Corneal pachymetry ( corneal thickness 450-500μ)

• Cycloplegic refraction to assess the exact power.

• Indirect Ophthalmoscopy for retinal examination

SURGICAL PROCEDURE• Anesthesia.

• Corneal marking

• Fixation of suction ring to raise IOP 65mm Hg.

• Cornea is moistened with BSS for smooth movement.

• Using a MICROKERATOME a thin flap(130-160μ) of corneal

tissue is raised.

• Suction pressure removed

• Flap moistened ,surface dried.

• Excimer laser reshapes the cornea by removing a pre-determined

precise amount of tissue.

• The corneal flap is repositioned nasally.

FLAP: Microkeratomes

• 1st generation

Linear cutting

• 2nd generation

Translational + rotational

• 3rd generation

Oscillatory/pendular

• 4th generation

Laser “bladeless”( hydrokeratome)

POST-OP

MANAGEMENT

• Antibiotics and corticosteroid therapy(4-6wk tapered course), tear

supplements

• Return 1 day, 1 wk., 3wks, 3 months, 6months

• Avoid water in eyes - no shower, hot tub or swimming- first 2wks

• Wear protective gear in any contact sports

• Avoid eye rubbing => dislocation of flap

• Enhancements / retreatment : 3-6 months later = adequate

stabilization of flap

COMPLICATIONSINTRAOPERATIVE COMPLICATIONS

1) Incomplete flap

• premature termination of microkeratome advancement

• inadequate globe exposure

• loss of suction during pass

• Never reverse microtome & then go forward, penetration to a deeper

level than initial pass.

2) Thin flap

• due to poor suction

• difficult to reposition & likely to wrinkle

3) Buttonholed flap

• If K > 50 D

• Ablation should not be performed, flap repositioned

4) Full thickness resection

5) Free cap –

• Flat/ small cornea, poor suction

• Small / decentered : procedure aborted

• Adequate size/ well centered : placed on conjunctiva with epithelial

side down & procedure completed

6) Epithelial defects – prevented by adequate lubrication

ABLATION COMPLICATIONS

1) Central islands – small central elevations

• Abnormal beam profile (broad beam lasers)

• particulate matter blocking subsequent laser pulses

2) Decentration – current lasres with incorporated eye-tracking & iris

registration systems

3) Under/ Over-correction

• excessive hydration : undercorrection

• desiccation : overcorrection & haze

POSTOPERATIVE

COMPLICATIONS1)Interface debris- mostly meibomian gland material

2) Flap displacement – first 24 hrs

lifted & repositioned

3)Night vision disturbances – haloes / glare

4)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

5)Punctate epithelial keratopathy

6)Diffuse lamellar keratitis (Sands of Sahara syn)

Advantage of LASIK over PRK

• No or minimal post op. pain

• Early recovery of vision

• Residual haze is unlikely

• High myopia(-6 to -30D) correction

Deep Lamellar Keratitis

• Grade I: This is a mild keratitis which is localized at the periphery with minimal to no symptoms.

T/T:Frequent topical steroids (prednisolone 1-2 hourly)

• Grade II: Moderate infiltrates extending to the central cornea causing decreased vision and photophobia occur.

T/T: Frequent topical steroids along with oral steroids to control the inflammation

• Grade III: Clumping of inflammatory cells which obscure the iris details and central infiltrates with a significant decrease in vision is seen.

T/T: Topical and oral steroids, lifting the flap to brush the stromal bed and the flap underface and irrigation to remove all the inflammatory cells and debris.

• Grade IV: Dense white central infiltrates maybe associated with corneal melting and loss of vision.

LASER SUBEPITHELIAL

KERATOMILEUSIS(LASEK)

• Introduced by Massimo Camellion in 1999

• Combined features PRK and LASIK

• Epithelial flap is removed by alcohol

Procedure

• Anaesthesia

• Trephining

• Alcohol(20%) treatment for 1 min

• Separation of epithelium

• Stromal ablation with excimer laser

• Reposition of epithelial flap

• BCL over flap

• Advantages over LASIK

• Disadvantages• More post op pain

• Post op. haze

• Delayed recovery

• Thin cornea

• Less corneal ectasia

• Flap related complications

less

• Myopic correction more

• Aberration less

• Post op. dry eye less

Epipolis Laser In Situ keratomileusis(Epi-

LASIK)

• Introduced by Pallikaris in 2003

• Same as LASEK except epithelial flap is created with

Epikeratome .

• Flap creation :-

Epikeratome move slowly over cornea(better control)

Plastic or stainless steel made separator pushes away the flap(

better separation)

Advantages over LASEK

• Use of epikeratome replace use of Alcohol(epithelio toxic)

• result:- Less pain

Faster healing

Less corneal haze

Wavefront-Guided (Customized) Excimer

Laser Refractive Surgery

• Definition: It is used to correct higher-order aberrations, in

addition to spherocylindrical correction.

• Zernike polynomials and Fourier transforms are used to analyse

the ocular wavefront.

• Wavefront-guided customized ablation produced better results in

terms of visual acuity and contrast sensitivity.

• Optical properties and image quality.

Types customized ablation

• Corneal topography guided ablation

• Wave front guided ablation

• C –LASIC based on both

Corneal topography

• Orbscan (placidodisc and

S/L imaging)

• Pentacam

Wave front aberrometry

Measure the distortion of light

wave in optics of eye by 3

principles.

• Hartman shack(charged-

coupled device (CCD) camera)

• Tscherning

• Ray tracing

Construction of Wavefront Aberration

Procedure of C-LASIC• Measurement of optical aberration

• Linking of data to laser machine

• Laser ablation

C-LASIC systemsConsist of

• Corneal topography & Wave front aberrometry systems

• Flexible laser delivery systems

• Eye tracking systems

Commercially available systems

• Zyopticx system

Zywave

Orbscan

Zylink

Technolas 217 Excimer laser

• ORK corwave system

• Nidek NAVAX LASIK system

Advantages of C-LASIC

• High quality vision (free of night glares , halo, improved

contrased sensitivity)

• Super vision (6/4) (d/2 reduced diffraction & higher order

aberration )

• Less invasive

• Correct irregular astigmatism

Orthokeratology• Nonsurgical reversible method of mouldingthe cornea with

overnight wear of unique rigid gas permeable contact lenses to

correct myopia.

• Initially 8 hrs./day(overnight)

• After desire correction achieved 3hrs/day

Indications

• Any age <-4Dsph or < -1.5Dcyl error

• <18yrs of age

• Unstable refractive

• Sports person

Disadvantages

• Longer result time

• Not a permanent solution

• Cost high

• Only for myopia

INTRASTROMAL CORNEAL RINGS

• makes use of intrastromal corneal ring segments = “INTACS”

(PMMA)

INTACS

The ring segments flatten cornea similarly to the way .

INTACS cont.• Initially indicated for low myopia (1-3D) and min astig < 1.00D

• Now=> Advocated for keratoconics

• C/I :- systemic diseases , pregnant& nursing mother, corneal

dystrophy

• complications -White cell reaction: responds to steroids

-Vascularization

Intraocular RS

• Phakic Refractive lenses

• Refractive lens exchange(RLE)

Phakic Refractive lenses • Implanted between the cornea and the lens

• Angle supported AC lens:-Fixated in the angle

• Iris claw lens:- catch the mid-peripheral iris with a claw

• PC lens:-Placed in the posterior chamber

Selection of patients for phakic IOLs

• Moderate to high myopes (>-9.00D) & hyperopes (> 4.5 D)

• where LASIK is contraindicated such as

Corneas thinner than 500 microns

Steep or flat corneas

Topographic change suggestive of keratoconus

• Endothelial cell density at least 2250-2500mm2.

• Anterior chamber depth (excluding corneal thickness) at least

2.8mm

• Angle width at least 30 degrees

• No eye pathology except refractive error

Advantages

• Safe

• Predictable

• Reversible

• Inexpensive

• Excellent vision even in dim light

• LASIK can be done for residual error

Refractive lens exchange(RLE)

• Fucala’s operation (Extraction of clear lens)

• Refractive cataract surgery

• Phacoemulsification & IOL implantation (-16D to -30D)

Indications

• Presbiopic age with Ref.

error and cataract

• High myopia(>10D) or

hyperopia(>5D)

C/I:-

• Retinal diseases

• Occupational night driver

Multifocal IOL

Collagen Cross Linkage

Anesthesia

8-9mm corneal epithelium scraped

out

Riboflavin 1% applied every 2 min.

for 30 mints

UV ray focused on stroma for 30

mins

Saline wash given

BCL applied

CONDUCTIVE KERATOPLASTY

• Non-laser refractive procedure

• Apply low energy Radiofrequency

wave

• Indicated in presbyopia & hyperopia

after 40 yrs. Of age

Radiofrequency energy

gentle heat in stroma

shrink collagen tissue

tight band formation

steepens cornea

correct presbyopia and hyperopia

• 8-32 spots apply in peripheral corneal stroma

Presbyopic bifocal LASIK

Multifocal LASIK With PARM technique – 8.5 to 9mm Flap

First perform hyperopic LASIK in 5 mm optic Zone making cornea Prolate

Followed by myopic LASIK in 4mm optic zone

THANK YOU