1. KERATOREFRACTIVE
SURGERIES
DR. KISHORE KHADE
Moderated by DR. UGAM USGAONKAR

2. APPLIED ANATOMY OF CORNEA
• EPITEHLIUM: composed of non keratinized
startified squamous epithelium of 4 to 6 layers
thickness. BM (lamina densa & lamina lucida), wing
cells and flattened top cells having microvilli.
• BOWMAN’S LAYER: condensed superficial layer of
the stroma, consists of randomly dispersed collagen
fibrils.
• STROMA: 500m thick consists of collagen producing
fibroblasts keratocytes , matrix & collagen lamellae.

3. APPLIED ANATOMY OF CORNEA
• DESCEMETS MEMBRANE: strong well defined
sheet in between stroma & endothelium.
• ENDOTHELIUM: plays an major role in active
transport & maintenance of normal stroma.

4. HISTORY
• In 1978 bore,myers & cowden were first in
USA to perform radial keratotomy & report
there results.
• Lamellar surgery were evolving
simultaneously, Jose Barraquer was the first
to correct refractive error through lamellar
surgery.

5. CLASSIFICATION OF
KERATOREFRACTIVE Sx
LOCATION ADDITION SUBTRACTION RELAXATION COMPRESSION
SUPERFICIAL EPIKERATOPHA
KIA
1.PRK
2. LASEK
---------- CORNEAL
MOLDING
INTRASTOMAL 1.KERATOPHAK
IA
2.INTRACORNE
AL LENSES
3.PINHOLE
APERTURES
1.LASIK LAMELLAR
KERATOPLASTY
PERIPHERAL INTRACORNEAL
STROMAL RING
WEDGE
RESECTION
RADIAL
KERATOTOMY.
1.THERMOKER
ATOPLASTY.
2.COMPRESSIO
N SUTURES

6. INDICATIONSINDICATIONS
• MYOPIA : Photorefractive karatoplasty.
LASEK.
LASIK.
HYPERMETROPIA : PRK/ LASEK 2-3D
LASIK upto 4D
Conductive keratoplasty
Laser thermal keratoplasty

7. INDICATIONSINDICATIONS
• ASTIGMATISM : Limbal relaxation/ arcuate
PRK/LASEK upto 3D
LASIK upto 5D
Conductive keratoplasty
• PRESBYOPIA : Conductive keratoplasty

8. Preoperative evaluationPreoperative evaluation
• MOTIVATION
• CYCLOPLEGIC REFRACTION
• SLIT-LAMP BIOMICROSCOPY.
• PUPIL SIZE.
• CORNEAL TOPOGRAPHY
• PACHYMETRY
• WAVEFRONT

9. Clinical significance of cornealClinical significance of corneal
topographytopography
• Indispensable tool for refractive
surgeons
– Preoperative screening
– Surgical planning
– Assessment of surgical outcomes
– Detection and management of complications
– Refinement and development of surgical
techniques

10. Principles of Corneal TopographyPrinciples of Corneal Topography
• Placido disc system
• Non-Placido disc system
–Scanning slit
–Rasterstereography
–Laser Holographic interferometry

11. FIGURE 2-17 BASIC CHARACTERISTICS OF AN AXIAL MAP
Simulated
keratometer
and astigma-
tism indicator
Statistical
index
indicators
Pupil size
indicator
Dioptric power
and radius
indicators
Vertex and
pupil distance
and location
indicators
1mm x 1mm
grid indicators
Center of map
(vertex) and
center of pupil
markers
Pupil marker

13. KeratometryKeratometry
• Advantages
• Accessibility
• Ease of use
• Precision is good
• Low cost
• Adequate for most contact lens fitting
• Limitations
• Small area measured: periphery and apex not measured.
• Assumes that the cornea is a spherical surface: accuracy is
questionable
• Irregular topography not described specifically and sometimes
undetected

14. WAVEFRONT
• Discovered nearly 400 years ago by
christopher scheiner.
• He demonstrated a technique to measure the
refractive error of the eye using a device
known as Scheiner disc.
• Visual acuity measuring device takes into
consideration tear film, anterior corneal
surface, corneal stroma, posterior corneal
surface, anterior crystalline lens

15. • posterior crystalline lens surface, vitreous and
retina.
• Prior to the advent of wavefront-sensing
devices, clinical refraction consisted of three
data points for each eye: defocus (spherical
error, myopia, or hyperopia), astigmatism,
and axis.

16. Wavefront Technology
Diagnostic devices :
1. higher-order aberrations :
field curvature, distortion, diffraction,
spherical aberration, chromatic aberration,
coma
2.refraction vs. wavefront refraction (refractive
map)
cf. keratometry vs. topographic map
Wavefront-guided refractive surgery

17. Types of aberrometer
• Hartmann shack system outgoing reflection
aberrometry)
• Tscherring system
• Ray tracing system.
• Ingoing adjustable refractometry.
• Double pass aberrometry.

18. Note the loss of dots centrally in a “moth-eaten” appearance and the overall
irregularity
of horizontal and vertical alignment of the spots of this eye with significant aberration.

19. EPIKERATOPHAKIA
• Is an form of refractive surgery on the cornea for the
correction of keratoconus, aphakia & high myopes.
• Gasset and kauffman in 1968 tried with plastic lens,
glued over the cornea. Unfortunately glue made the
corneaq opaque.
• Werblin and kauffman later devised using lathe cut
donor corneal lenticule mainly in peadiatric aphakic
patients.
• With planopower lenticule was developed to treat
keratoconus like onlay lammellar keratoplasty.

20. EPIKERATOPHAKIA
• Corenal epithelium is thoroughly denuded by
rubbing with cellulose sponge.
• 7mm to 7.5mm trephine is used to incise the
patient’s cornea partially to the depth of 0.2
to 0.3mm.
• Rehydrated epikeartophakia lenticule is
sutured into the host cornea.
*

21. ALLOPLASTIC REFRACTIVE
KERATOPLASTY
• This technique involves intrastromal implantation of
hydrogel materials with specific curvature.
• Alloplastic material like polysulphone is placed
between epikeratophakia graft & BM alters the
refractive power by changing the refractive index of
stroma.
• Shape of lenticule is concave or convex depends on
refractive status of eye ie: myope/ hypermetrope

22. KERATOPHAKIA
Lenticule with predetermined power is made
from the donor cornea.
This lenticule is placed over the host prepared stroma
with convex surface anteriorly.
The previously removed stromal disk is sutured over
the lenticule.
Corneal decompensation may lead to postop
opacification, perforation & flattening of Ac may
occur. PK may require for the complication.

24. EXCIMER
• Trokel, srinivasan & barren first suggested the
use of excimer for corneal surgery.
• Excimer derived from term excited dimer of
inert gases.
Leads to emission of high energy photon of UV
light having 6.4eV.
various excimer lasers are: argon fluoride
193nm,kypt cl 222nm, kypt fl 249, xenon cl
308, xenon fl 351.

25. Corneal tissue interaction
• Carbon- nitrogen bonds which forms the
peptide in proteins is broken by the highly
excited state of an inertgases.
• The photon induced molecular decomposition
results in abalative photo decomposition.
• The above mentioned process if precisely
controlled, restricted, gives optically smooth,
with minimal scarring with appro depth
abalation.

26. Photo refractive keratoplasty
• Patients selections;
motivation
age >18years
refraction stability
Ocular pathology
systemic condition
ocular
Keratoconus
Advanced keratitis sicca
Lagophthalmos
Corneal vascularisation
Pathological changes in retina & lens
Herpes
depressed Corneal scar
Progressive myopia.
Systemic
Collagen vascular disease
Immunodeficiency
Keloid formation
Dm
Pregnancy & lactation

27. PREOPERATIVE EVALUATION
• Visual acuity with cycloplegic refraction
• Complete ophthalmic & medical history.
• Keratometry / topography / pachymetry
• Pupil size and diameter in dim light.
• Applation tonometry
• Test for dry eye & lacrimal examination

28. PRK
• Laser caliberation & prechecks
• Ppd & topical anesthesia
• Determination of optical centre.
• Removal of epithelium
• Stromal ablation
• Postop medication
• Placement of soft contact lens
• ***

29. COMPLICATIONS
• Intra OP: Error in laser programming.
Incompelete epithelial removal
Decentered ablation.
Post OP :
Early
Delayed wound
healing
Infection
NSAIDS infiltrates
AB precipitates
CORNEAL melts
INTERMED 2wk-6 mnth
Over/under corr
Regression
Streep corneal islands
Scars
Steriod induced
complicationss
LATE >6 months
Steriods induced
Scars
Halos/ glares
Visual fluctuations
Corneal haze

30. LASEK
• Laser subepithelial keratomileusis (LASEK) is a
relatively new refractive surgical technique that
purportedly combines the advantages of laser in-situ
keratomileusis (LASIK) and photorefractive
keratectomy (PRK).
• In 1996, Azar [8•] performed the first LASEK
procedure, which he called “alcohol-assisted flap
PRK.” Later it was renamed LASEK by Camellin, who
popularized his own version

31. LASEK
• LASEK is in essence a hybrid of PRK and LASIK that
may provide relatively quick visual recovery, while
eliminating virtually all flap-related complications.
• The LASEK procedure is based on chemically reducing
the corneal epithelial adhesion to the underlying
Bowman’s layer by the application of dilute ethanol.
• 8.0-mm diameter circular marker with an 80μm deep
cutting edge, designed to create a 270° superficial
punch cut in the epithelium.

32. LASEK
• The denuded corneal surface is then ablated with the
excimer laser as in standard PRK.
• flap is gently repositioned over the central cornea
with a blunt instrument, such as a Barraquer iris
sweep.
• A therapeutic soft contact lens is placed onto the
cornea.

33. LASIK
• Initially described by Pallikaris in1990.
• Preoperative consideration;
Patient selection.
Stability of refraction.
Fundus
Corneal thickness/ conus
Patients anxiety/ sedation.

34. LASIK procedure
• Anesthesia : topical with 1% proparacaine or
4% xylocaine.
• Corneal marking: ensure proper realignment.
• Suction ring: placed on the eye & centerd over
the limbus. IOP rises over 60mm hg.
• Microkeratome: when adequate pressure is
obtained surface is lubricated with anesthesia
not saline.

35. Microkeratome is slide over surface to raise the
epithelial flap.
• Excimer laser reshapes the cornea by
removing a pre-determined precise amount of
tissue.
• The corneal flap is repositioned iris sweep –
no stitch required.
• Fluence test.
• ***

36. CORNEAL BIOMECHANICS
• Layered corneal is permanently severed following
surgery.
• This reduces the tension in the remaining peripheral
segments allowing expansion of peripheral layers.
• Peripheral expansion results in higher order
aberrations.
• Topography allows to visualise actual change in
shape that occured following the ablation.
• Wavefront helps in to fully characterised shape
changes & resultant functional response.

37. Customized Refractive Surgery
Functional customization based on
patient’s need
Anatomical customization
Optical customization

38. Customized Refractive Surgery
Functional customization based on pt’s need
1. age
2. presbyopia
3. occupational and recreational needs
4. refraction
5. psychological tolerance

39. Customized Refractive Surgery
Anatomical customization
1. corneal diameter and thickness
2. pupil size
3. anterior chamber depth
4. anterior and posterior lens shape
5. axial length

40. Customized Refractive Surgery
Optical customization
1. customization based on corneal topography
2. customization based on wavefront
measurement

41. Customized refractive surgery
1}SCANNING SPOT: spot size of 1mm or lesser to treat
4th
order aberrations with optical zone diameter of
6mm.
2}SCANNING SPOT SHAPE:
(a) Gaussian beam shape: it allows very smooth
overlape creation of ablation zone.
(b)Top HAT: gives rise to spikes & valleys in the
ablation profile.
3}SCANNING SPOT RATE: small spots utilise 200Hz
energy.

42. 4} SPOT PLACEMENT: spot is best when it is non-
sequential such that one spot is not placed
next to the precedding spot.
EYE TRACKING:
1) SAMPLING RATE.
2)LATENCY.
3) TRACKER TYPE.
4) CLOSE-LOOP VERSUS OPEN LOOP TRACKING.

43. Wavefront-Guided Refractive
Surgery
“ Super Vision ” ( 20 / 10 )
Eliminating surgically induced aberrations is the
first step to super vision.
Seiler T : increase in higher-order aberrations
after standard LASIK : 144 %
after wavefront-guided LASIK :
40 %
Adding wavefront informations is helpful in cases
within 0.25 D of the intended correction.

45. FEMTOSECOND LASER
• The femtosecond laser is a mode-locked, diode
pump,neodynium-glass laser. It operates in the
infrared wavelength range, at 1053 nm. It uses a spot
size of less than 3 μm and produces tissue disruption
(Photodisruption) at a specified and precise level
within the corneal stroma. The laser produces
cavitation bubbles consisting of water and carbon
dioxide which are ultimately absorbed through the
corneal endothelium.

46. FEMTOSECOND LASER
• A unique feature of the femtosecond laser is its
ability to produce tissue disruption at very low
energy settings. This is due to the very short pulse
width, or pulse duration, associated with the laser
(600 to 800 fs), and to the very rapid pulse
repetition, or speed, of the laser (15,000 to 60,000
pulses per second).

47. FEMTOSECOND LASIK
• Femto laser has been devised to raise LASIK
flaps
MECHANICAL FEMTOLASER
Mechanism Cut from side to side with
globe pressure
Creates an interface cut
at predetermined depth
Flap Meniscus flap Planar flaps
Flap thickness Depends on suction ring
thickness,corneal
diameter & curvature
Independent of any such
parameters
Size & shape Makes an D shape flap Well centered flap is
created
Complications Free flap, button hole are
common
Light sensitivity,
photophobia common
but self limiting

48. FEMTOSECOND DISADVANTAGES
• Longer suction time
• More flap manipulation
• Opaque bubble layer may interfere with excimer
ablation
• Bubbles in the anterior chamber may interfere with
tracking and registration
• Increased overall treatment time

49. FEMTOSECOND DISADVANTAGES
• Difficulty lifting flap >6 months
• Increased risk of diffuse lamellar keratitis
• Increased cost
• Need to acquire new skills
• Delayed photosensitivity or good acuity plus
• photosensitivity (GAPP), which may require
• prolonged topical corticosteroid therapy

50. Contraindications of LASIK
• Pre existent anamolies- keratoconus.
• Inappropriate parameters; power/
pachymetry/ pupil size.
• Degenrative eye conditions: lupus/glaucoma/DR/
RA.
• Infections.
• Severe dry eye.
• RD
• Pregnancy/ lactating.
• AGE and change in refraction.

51. COMPLICATIONS OF LASIK
• Overcorrection: Myopic or hyperopic surface
ablation typically undergoes some degree of
regression for at least 3- 6 months.
• Undercorrection: Undercorrection occurs much
more commonly at higher degrees of ametropia
because ofdecreased predictability due to the
greater frequency and severity of regression.
• Central Islands: A central island appears on
computerized corneal topography as an area of
central corneal steepening

52. • Optical Aberrations :Some patients report optical
aberrations after surface ablat ion and LASIK,
including glare, ghost images, and halos
• Decentered Ablation
• Corticosteroid-Induced Complications
• Dry Eye and Corneal Sensation
• Infectious Keratitis
• Persistent Epithelial Defects
• Sterile Infiltrates

53. • Corneal Haze
• Epithelial Sloughing or Defects
• Striae
• Traumatic Flap Dislocation
• Diffuse Lamellar Keratitis

54. LASIK
1 Faster visual recovery –
1 day
2 No Post operative pain
3 Good for low and high
myopes
4 Predictable and stable
5 Not good for contact
sports
LASEK/PRK
1 Visual recovery – 1
week
2 Mild to Moderate post
op pain
3 Low myopia, thin
corneas
4 Less predictable,
modulation
5 Contact sports, military

55. EPI-LASIK
• Surface ablation in which a viable epithelial flap is
raised.
• The flap is raised at the level of the LAMINA DENSA,
the whole basement membrane remains attached to
the epithelium, increased survival of basal cells.
• Alcohol assited seperation occurs at the level of
lamina lucida and reduces survival of the epithelial
cells.
• ****

57. CORNEAL RINGSCORNEAL RINGS
• In cases like keratoconus structural
integrity is increased by :
INTACS
C3R

58. INTACSINTACS
• Intacs are small semicircular plastics rings of various
thickness inserted in the corneal stroma.
• They are used for the corrections of 1-3D.
• They work by flatting of central portion of the cornea
there by correcting myopic refractive error.
• They smoothen out corneal irregularities
which improves the quality of visison.

59. CORNEAL COLLAGEN CROSSCORNEAL COLLAGEN CROSS
LINKING with RIBOFLAVINLINKING with RIBOFLAVIN
• C3R is a procedure which uses RIBOFLAVIN as the
photosensitiser with UV rays of 365nm.
• UV light increases the number of collagencross
linking fibres which are the anchors within the
corneal stroma.
• RIBOFLAVIN drops are placed every 2 mins, 30 mins
prior to UV-A radiation.
• After the procedure bandage contact lens is used.

60. C3RC3R
• ADVTG: increase intigrity & progression
reduce astigmatism & myopia
enhance contact lens fitting
C/I : keratometry >60D
pachymetry < 400 m
infection/ corneal opacity (central)
<12 yrs or >40 yrs

61. Laser thermal keratoplasty
• Thermal tissue necrosis gives rise to enhanced
corneal remodelling, thereby limiting effect &
causing regression.
• Ho: YAG laser uses wavelength of 2.13mm ,pulse
duration of 200-300ms laser is used to create
paracentral corneal coagulation & shrinkage in the
controlled manner

62. • Contact mode : fibr-optic probe to deliver
laser pulses to premarked points on the
cornea.
• NON- Contact mode: A slit lamp delivery
system is used to deliver pulses in an
octagonal pattern on the cornea
simultaneously.
Laser thermal keratoplasty

63. CONDUCTIVE KERATOPLASTYCONDUCTIVE KERATOPLASTY
• Utilises radiofrequency energy placed in the
periphery of the cornea to cause collagen shrinkage
& steepen the central cornea.
• 450 x 90 mm2 dimension tip radiofrequency is
delivered in the cornea causing thermal effect.
• +0.75 – +3.25D correction of cycloplegic refraction
with less then -0.75D of astigmatism.
• Age >40 yrs

64. RADIAL KERATOTOMY
• Radial incisions were made to modify the surface of
the cornea by Sato & his associates in 1894.
• To correct myopia, astigmatism & keratoconus.
• Radial incisions were made from periphery to the
paracentral area .
• However it was associted to many complications like
posterior extension leading to posterior keratotomy,
bullous keratopathy due to several of these
complications this procedure is rarely done now

65. RADIAL KERATOTOMY

66. Limbal Relaxing Incisions
• Limbal Relaxing Incisions (LRI) are a refractive
surgical procedure to correct minor astigmatism in
the eye.
• Incisions are made at the opposite edges of
the cornea, following the curve of the iris, causing a
slight flattening in that direction.
• They are simpler and less expensive than laser
surgery such as LASIK or photorefractive
keratectomy.

67. Over view
EPIKERATOPHAKIA
RADIAL KERATOTOMY
Limbal Relaxing Incisions
THERMOKERATOPLASTY
INTRACORNEAL STROMAL RING
PRK
LASEK
LASIK

68. THANKYOUTHANKYOU