REFRACTIVE SURGERIES

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REFRACTIVE SURGERIES

• Dr.Jyoti Shetty
• Medical Director,
• Bangalore West Lions Superspeciality Eye Hospital

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CLASSIFICATION
-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 IOLs
Combination of the two
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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

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• Types of lasers used-
• Excimer-Excited dimer of two atoms
• -an inert gas(Argon)
• -Halide(Fluoride)
• which releases ultraviolet energy at193nm for
  corneal ablation

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• Non-Excimer solid state lasers-
• 210nm Q switched diode pumped laser (laser off)
• 213 nm Q switched diode pumped laser(Pulsar)

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

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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

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• CCT such that minimum safe bed thickness
  left(250-270µ).Post op Corneal thickness should
  not be lt410µ.
• Cornea not too flat or steep.lt36D orgt49D(Poor
  Optics).

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CONTRAINDICATIONS

• Systemic factors-
• Poorly controlled IDDM
• Pregnancy/lactation
• Autoimmune / connective tissue disorders(RA,SLE,PA
  N 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)

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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)

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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
  

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• 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.

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• 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

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• Pachymetry -For CCT (Ultrasound/Optical)
• Contrast Sensitivity testing for pre-operative
  baseline.

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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

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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.

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• 2nd step-Resection of corneal flap

Microkeratome
Femtosecond Laser (Intralase)
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• 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.

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• 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)

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• Flap has vertical edges so reduced epithelial
  ingrowth.
• Microkeratome flap thicker in periphery and
  thinner in the centre.Not so with
  Intralase(Planar).

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• 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-

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

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

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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

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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.

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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
• -Dont violatecorneal
  topography diagnosis of forme-fruste keratoconus

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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

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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)

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COMPLICATIONS OF LASIK

• Flap Complications-
• Button Hole-If Kgt50D,due to central corneal
  buckling.
• .

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• Irregular thin flap-Inadequate suction/old blade
• Short Flap-Hinge encroaches on visual axis-Due to
  jamming of microkeratome with hair/FB

SHORT FLAP
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• Free Cap-Due to flat pre op K(lt38D).

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• .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
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• Microstriae-Flap in position but fine wrinkles
  seen superficially
• -Due to large myopic ablation
• -Rx- Observe.They resolve
  spontaneously

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

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• 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

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• Grade 1-
• Focal involvement - Normal V/A.
• Rx Intensive topical steroids.

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• II Diffuse involvement Normal V/A.
• Rx-Add systemic steroids.

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• III Diffuse confluent granular deposits-
• Reduced V/A.No AC reaction.
• Rx-Same as aboveAntibiotics
• IV - Diffuse confluent granular deposits intense
  central striae.
• Marked Reduced V/A
• Rx-Interface irrigation above

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

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• Infection-Potential complication as any surgical
  procedure

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• 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

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• Classification-
• GRADE 1-Faint white line lt2mm from flap edge
• GRADE 2-Opaque cells lt2mm from flap edge with
  rolled flap edge
• GRADE 3-Grey to white fine opaque line extending
  gt2mm from flap edge.
• GRADE 4-If ingrowth gt2mm from edge with
  documented progressionLift flap and remove the
  sheets of epithelium.Can use MMC.

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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.

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• LASEK-Camellins Technique-
• 20 absolute alcohol used for 20-35s. To raise
  epithelial flap.
• Flap reposited after ablation

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• EPILASIK- Epithelial keratome used to lift
  epithelial flap of about 60-80µ thick.
• Epithelial keratomes use
• - PMMA blades
• -Metal Epithelial Separator

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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.

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7
6
5mm
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• Drawbacks-
• Regression and retreatment in 100 cases after 6
  months.
• Induced cylinder gt1D reported in many cases.
• Usually done in one eyeMany have intolerance to
  monovision.

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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.

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AcuSof Corneal inlay
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Phakic IOLs

• An intra-ocular lens is placed inside the eye in
  front of the patients natural lens.
• These are available in three types
• Anterior chamber angle fixated IOL Nuvita
  (Bausch Lomb), Kelman duet, I care (corneal),
  Vivarte (Ciba vision)
• Iris supported phakic IOL Verisyse/ Artisan
  (AMO/Ophtec)
• Plate lens that fits between the iris the
  crystalline lens Starr implantable contact lens
  (ICL), PRL (Ciba).

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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 gt2000cells/cumm
• No other ocular pathology

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Contraindications

• Myopia other than axial myopia
• Corneal dystrophy/ Endothelial cell count
  lt2000cells/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

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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
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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
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Anterior Chamber Phakic IOL
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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 patients refraction changes.

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Iris fixated phakic IOL Verisyse Phakic IOL

• Most commonly used phakic IOL
• One-piece design

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Verisyse Phakic IOL
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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

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Veriflex (artiflex)

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

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Posterior chamber lenses

• These phakic IOLs are placed in the posterior
  chamber between the iris the crystalline lens.
  These are
• Starr ICL
• Cibavision PRL

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STAAR ICL

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

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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.

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Complications

• ICL decentration
• Pupillary block
• Pigment dispersion
• Subcapsular cataract

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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.

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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.

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