refractive surgery

1. Dr.Subhadri Manna
PGT,CNMC&H

2. 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

3. 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

4. 5.Corneal implants
Intracorneal contact lenses(ICL)
Intrastromal corneal ring
segments(Intacs)
6.Corneal tissue moulding
Orthokeratology
B. Lens-based
refractive procedures
Phakic refractive lenses(PRL)
Refractive lens exchange(RLE)
c. Combined lens and
corneal refractive
procedures
Bioptics
Trioptics

5. PREOPERATIVE EVALUATION
Involves-
• Screening,
• History taking
• Preoperative examination & counselling

6. 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

7. TOPOGRAPHIC ANALYSIS
• Keratometry (measures central 3 mm corneal curvature)
• Computerized Videokeratography (only way to uncover early KC)

8. PACHYMETRY
• measuring thickness of cornea.
ORBSCAN DEVICE
• Optical device
• Advantage – can provide thickness measurements throughout the
cornea.

9. 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

10. 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

11. Radial keratotomy
Svyatoslav Fyodorov, a Russian national, is accredited with the
development of modern radial keratotomy (RK).

12. 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

13. 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.

14. 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 .

15. 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

16. 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)

17. 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.

19. Laser used RS
• Excimer laser(ArF) - 193nm
• Solid state diode laser -680nm
• Femtosecond laser(Nd:glass) -1053nm

20. 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

21. 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.

22. 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

23. 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

26. PHOTOREFRACTIVE
KERATECTOMY
• First widely used procedure with the excimer laser
(1987)

27. 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

28. 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

29. 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

31. Post op. care
• 24 hrs patching
• Cycloplegic
• Steroid
• Topical steroid
• Tear drop
• BCL

32. 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.

33. 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.

34. 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

35. 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.

36. 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

37. 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.

39. FLAP: Microkeratomes
• 1st generation
Linear cutting
• 2nd generation
Translational + rotational
• 3rd generation
Oscillatory/pendular
• 4th generation
Laser “bladeless”( hydrokeratome)

41. 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

42. COMPLICATIONS
INTRAOPERATIVE 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

43. 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

44. 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

45. POSTOPERATIVE
COMPLICATIONS
1)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)

47. 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

48. 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.

49. LASER SUBEPITHELIAL
KERATOMILEUSIS(LASEK)
• Introduced by Massimo Camellion in 1999
• Combined features PRK and LASIK
• Epithelial flap is removed by alcohol

50. Procedure
• Anaesthesia
• Trephining
• Alcohol(20%) treatment for 1 min
• Separation of epithelium
• Stromal ablation with excimer laser
• Reposition of epithelial flap
• BCL over flap

51. • 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

52. 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)

53. Advantages over LASEK
• Use of epikeratome replace use of Alcohol(epithelio toxic)
• result:- Less pain
Faster healing
Less corneal haze

54. 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.

55. 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

57. Construction of Wavefront Aberration

59. Procedure of C-LASIC
• Measurement of optical aberration
• Linking of data to laser machine
• Laser ablation
C-LASIC systems
Consist of
• Corneal topography & Wave front aberrometry systems
• Flexible laser delivery systems
• Eye tracking systems

60. Commercially available systems
• Zyopticx system
Zywave
Orbscan
Zylink
Technolas 217 Excimer laser
• ORK corwave system
• Nidek NAVAX LASIK system

61. 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

62. 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

63. 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

64. INTRASTROMAL CORNEAL RINGS
• makes use of intrastromal corneal ring segments = “INTACS”
(PMMA)

65. INTACS
The ring segments flatten cornea similarly to the way .

67. 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

68. Intraocular RS
• Phakic Refractive lenses
• Refractive lens exchange(RLE)

69. 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

71. 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

72. Advantages
• Safe
• Predictable
• Reversible
• Inexpensive
• Excellent vision even in dim light
• LASIK can be done for residual error

73. 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

74. Multifocal IOL

75. Collagen Cross Linkage

76. 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

77. CONDUCTIVE KERATOPLASTY
• Non-laser refractive procedure
• Apply low energy Radiofrequency
wave
• Indicated in presbyopia & hyperopia
after 40 yrs. Of age

78. 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

79. 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

80. THANK YOU