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REFRACTIVE
SURGERIES
Dr. NEHA PATHAK
2 nd year PG Resident
Deptt. of
Ophthalmology
Govt. Medical College,
Kota
Eye’s refractive power determined by 3
variables - 1. Power of the cornea
2. Power of the lens
3. Length of the eye
EMMETROPIA
- Optically normal
eye
- Image of the object
being viewed is
focused on retina
- Resulting in clear &
sharp vision
AMMETROPIA – A condition of refractive
error
- Causes blurred vision as
image is
not focused on retina
1. Myopia
- Near-sightedness
Image is focused
in front of retina
2. Hyperopia
- Far-sightedness
- Image is focused
behind retina
3. Astigmatism – Refraction varies in different
meridia
- Rays of light entering eye
can’t converge to
a point focus but form focal
lines
4. Presbyopia – Eye sight of old age
- Physiological insufficiency of
accomodation
leading to progressive fall in near
vision
- Mechanism :
1. Senile lens hardening
PUPIL SIZE & CENTRATION OF
REFRACTIVE PROCEDURES






Rays of light from a point source are
refracted by the area of cornea overlying
the entrance pupil . This area is c/a the
corneal optical zone .
Entrance pupil - Virtual image of
anatomical pupil formed by magnifying
effect of the cornea – larger & closer to
cornea.
Optical zone in a keratorefractive procedure
: “The area of central cornea that bears the
refractive change caused by the surgery”.
FACTORS DETERMINING
CENTRATION OF
KERATOREFRACTIVE PROCEDURES

Foveal photoreceptors
orient themselves towards
centre of the pupil (StilesCrawford effect), even if
entrance pupil becomes
eccentric.
 Pupillary dilatation
under mesopic & scotopic
conditions, beyond the
edge of the optical zone
causes edge glare & haloes
=> Favour the centration of
KR procedures on the

CLASSIFICATION OF REFRACTIVE
PROCEDURES
REFRACTIVE SURGERIES

CORNEA BASED









R.K.
PRK
LASIK
EPILASIK
LASEK
Conductive
Keratoplasty
Corneal Inlays
and rings

LENTICULAR BASED






Clear Lens
extraction for
myopia
Phakic IOL
Prelex Clear
Lens
Extraction with
use of
Multifocal
IOL’s

COMBINED(BIOPTICS)

•

Combination
of the two
KERATOREFRACTIVE SURGICAL
PROCEDURES
LOCATION

ADDITION

SUBTRACTIO
N

RELAXATION COMPRES
SION

SUPERFICIAL

1.EPIKERATO
PHAKIA
2.SYNTHETIC
EPIKERATOP
HAKIA

1.PRK
2 LASEK
3.Epi-LASIK

----------

INTRASTOMAL

1.KERATOPHA
KIA
2.INTRACORN
EAL LENSES
3.PINHOLE
APERTURES

1.LASIK
2.WAVEFRONT
GUIDED LASIK
3.IntraLASIK
(IntraLase)

LAMELLAR
KERATOPLAST
Y

PERIPHERAL

INTRACORNE
AL STROMAL
RING

WEDGE
RESECTION

1.RADIAL
KERATOTOMY
2.ARCUATE
KERATOTOMY

CORNEAL
MOLDING

1.THERMOK
ERATOPLAS
TY.
2.COMPRES
SION
SUTURES
PREOPERATIVE EVALUATION
Involves 1)Screening,
 2)History taking,
 3)Preoperative examination &
 4)counselling



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,EhlerDanlos
-Keloids
 Systemic Infection-(HIV,TB)
 Drugs-Azathioprene,Steroids(Slow
wound healing)
-Antihypertensives,
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
OPHTHALMIC EXAMINATION









VISUAL ACUITY – Distance & Near : with &
without
correction
REFRACTION – Current spectacle correction
- Manifest refraction
- Cycloplegic refraction (1%
cyclopentolate )
EXTERNAL EXAMINATION – Ocular dominance
- Ocular
motility
- Gross external
examination
SLIT-LAMP EXAMINATION – Fluorescein & vital
stain
JONES’ BASAL TEAR SECRETION RATE
TOPOGRAPHIC ANALYSIS
1) Keratometry (measures
Videokeratography
central 3 mm corneal curvature)
early KC)

2) Computerized
(only way to uncover
PACHYMETRY
- measuring thickness of cornea
ULTRASONIC
PACHYMETRY
Recommendations
for minimum
bed thickness
(250µ) based
upon ultrasonic
devices
1)
2) ORBSCAN
DEVICE
- Optical device
- Advantage – can
provide thickness
measurements
throughout the
cornea
EPIKERATOPHAKIA






EPIKERATOPLASTY/ ONLAY LAMELLAR
KERATOPLASTY
Removal of epithelium from central cornea
 peripheral annular keratotomy 
lyophilized donor lenticule is reconstituted
& sewn into the annular keratotomy site
Adv. - simplicity & reversibility
Disadv – irregular astigmatism, delayed
visual recovery, prolonged epithelial
defects.
Abandoned procedure now.
Radial Keratotomy (RK)






Series of 4-8
deep, radial
corneal stromal
incisions
Weaken the
paracentral &
peripheral cornea
& flatten the
central cornea
I/C- keratoconus
astigmatism
LONG-TERM
COMPLICATION
S
- Bullous
keratopathy
secondary to
endothelial cell
loss
- Low stability of
refraction

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








No microkeratome
involved
No flap created
Ultimate visual
results similar to
LASIK
Longer recovery
period (> 2 weeks)
Complications
similar to LASIK;
Haze
LASIK (Laser-assisted in situ
keratomileusis)






Most commonly performed
refractive surgery
Combines lamellar corneal
surgery with accuracy of
the excimer laser
Excimer laser ablation of
corneal stroma beneath a
hinged corneal flap that
is created with a
mechanical femtosecond
laser microkeratome
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 1 st 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
Types of lasers used
Excimer

: for corneal stromal

ablation
Non-Excimer solid state lasers : for
flap creation
EXCIMER LASERS
 Excited





dimer of two atoms
-an inert gas(Argon)
-a Halide(Fluoride)
 releases ultraviolet energy at193nm
Reshapes corneal surface by removing
anterior stromal tissue
Process – Non-thermal
Ablative
Photodecomposition
Laser delivery patterns :
1) Broad-beam lasers - deliver a large diameter
beam of laser – starts small & expands as the laser
is delivered
ADV. Less operative time
DISADV. Creation of central islands ( difficulty to
maintain
uniform consistency over a larger diameter beam)
2) Scanning excimer lasers:
- Scanning-slit laser
- Flying spot laser
Provide smoother ablation than the old
broad-beam lasers


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.
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 -15D
Hyperopia –upto +6D
Astigmatism-upto 6D







CCT such that minimum safe bed thickness
left(250-270µ).Post op Corneal thickness
should not be <410µ.
Extreme keratometric values ( flatter than
41.00 or steeper than 47.00) avoided
Videokeratoghic clues to a KC suspect:
K value > 47.2 D,
Inferior steepening of > 1.4 D,
difference of > 1.9 between K values of
both eyes
Contact lens free period before
examination :
3-4 wks for rigid contact lens wearers
2 wks for soft contact lens wearers
BASIC MECHANISM





Normal cornea – prolate shape ( greater
curvature centrally )
Myopic correction – create an oblate shape
by central corneal laser ablation
Hyperopia - Excimer laser ablation at midperiphery  steepening of central cornea
Mixed astigmatism –
1)Bitoric LASIK technique – flattening
the steep meridian with paracentral
ablation over the flat meridian
2)Cross-cylinder technique – dividing
cylinder power into 2 symmetrical parts –
half of the correction is treated on the
positive meridian & half on the negative
MUNNERLYN EQUATION






Roughly defines the depth of ablation
required to achieve a specific amount of
correction
For 1 D correction  depth of ablation
required (in microns) one-third of the
square of diameter (in mm)
So each spherical equivalent diopter of
myopic correction performed at a 6mm
optical zone will ablate 12 microns of
tissue
OPERATIVE PROCEDURE











5mg Diazepam 5-10 min before procedure
Verification of entered computer data before
starting procedure
Topical anasthesia-Proparacaine 0.5%,
Lignocaine 4%.
Surgical Painting and draping
Lid speculum with aspiration
Proper centration over pupil & maintenance
by the aid of Tracking systems & iris
registration
C/L eye taped shut to prevent cross-fixation
1 st step - Creation of flap





Corneal marking
with ink
Adequate placement
of suction ring
using bimanual
technique
Suction
engagement by foot
control
Adequate IOP (>65mmHg) which is
necessary for the microkeratome to
create a pass and resect the corneal
flap.
 verified by BARRAQUER
TONOMETER
 confirmed by patient – temporary
loss of visualization of fixation light

2nd step - Resection of corneal
flap

Artficial tear drops instilled


MICROKERATOMES

1) Steel 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.
2) Waterjet Keratome
-Less debris & collateral damage than blade
3) Laser Keratome (IntraLase)
-

Solid-state laser
1053 nm wavelength
3 µm spot size- high precision
Uses brief Femtosecond laser pulses to
cause disruption in a lamellar plane
- Needs lower vacuum & any hinge can be
made
- Can make flaps as thin as 100µ(Sub
Bowmans
Keratomileusis)
- Flap has vertical edges –so reduced
epithelial ingrowth.
- Steel Microkeratome flap thicker in
periphery and thinner in the centre. Not so
with Intralase(Planar).
3 rd Step-Delivery of Laser After

flap is lifted,assessment of
residual corneal bed thickness usin USG
pachymetry
 laser is applied to the stroma according
to the ablation profile calculated by the
machine.
 Excimer Laser beam is delivered by the
following ways depending on the
machineBeam Delivery

Broad Beam

Scanning Slit Beam

Flying Spot


Most machines employ a flying spot
to deliver laser with the help of
incorporated eye tracker or iris
registration.
4 th step-Reposition Of the Flap After

irrigating interface ,flap reposited
 Sweeping movements with a wet cellulose
sponge
 From the hinge towards the periphery of
flap
 Adhesion verified – stretching the flap
towards gutter
 Topical antibiotic, steroid & lubricant
instillation  transparent plastic
shields
WAVEFRONT-GUIDED
(CUSTOMIZED) EXCIMER LASER
REFRACTIVE SURGERY


To correct higher-order aberrations in addition to
lower- order sphero-cylinder corrections
- LOWER ORDER Nearsightedness
Farsightedness
Astigmatism
- HIGHER ORDER Spherical aberration
Chromatic aberration
Diffraction
Curvature of field
Coma
Trefoils
Quadrifoils


Higher order aberrations occur in
visually significant manner in 1015% of population



Cannot be corrected with
spherocylinder lens or conventional
laser refractive surgery



Correction – Hard contact lenses
- Wavefront-guided
customized
MEASUREMENT OF WAVEFRONT
ABERRATIONS (ABERROMETRY)
ABERROMETER

OUTGOING ABERROMETERS

Analyze outgoing light that emerges
From retina & passes through the
Optical system of eye
Hartmann-Shack Aberrometer
(most commonly used)

INGOING ABERROMETERS

Analyze ingoing light that forms an
image on the retina
Tscherning Aberrometer
Ray Tracing Aberrometer
Scanning Slit Refractometer
ANALYSIS & DECOMPOSITION OF
WAVEFRONT ABERRATIONS INTO
COMPONENTS

ANALYSIS OF ABERRATIONS

ZERNIKE POLYNOMIALS
(most commonly used)

FOURIER ANALYSIS
CUSTOMIZATION OF ABLATION
PROFILE
TYPES OF CUSTOMIZATION

TOPOGRAPHY-GUIDED ABLATION
(Conventional laser surgery)

WAVEFRONT-GUIDED ABLATION
(Customized laser surgery)


Conversion of wavefront measurement
data to an ablation profile 



Imported to an excimer laser 



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



Precise wavefront-guided ablation
during LASIK is achieved
CUSTOMIZED ABLATION
PLATFORMS
1) Nidek Advanced
Vision
EXcimer Laser
system





OPD-Scan optical path
difference scanning
system (combines
measurement of
corneal topography &
aberrometry)
Develops customized
ablation profile
EC-5000CX II excimer
2) VISX S4
CustomVue
Platform (Santa
Clara, CA)


Wavescan
wavefront system –
Hartmann-Shack
wavefront sensor



STAR S4 excimer
laser sytem
delivers customized
laser ablation
3) Alcon
Customized
Cornea
Platform
 LADARWave
wavefront
sensor ( a
HartmannShack
eberrometer)
 LADARVision
system to
deliver
customized
4)Bausch and Lomb
Zyoptix System
 Diagnostic part :
- Zywave aberrometer –
a Hartmann-Shack
sensor
- ORBSCAN – 3D
information about
cornea
 Truncated Gaussian
beam laser – 2 sizes –
 2mm – corrects
majority of refractive
error in short time
 1mm – more specific
ablation pattern on
5) Allegretto
Wavefront-Guided
Ablation


Allegretto wave
analyzer –
Tscherning
Aberrometer



Allegretto excimer
laser system – high
repetition rate spot
laser (200Hz) with
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
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
a) abnormal beam profile (broad beam lasers)
b) particulate matter blocking subsequent laser
pulses
c) increased hydration
2) Decentration – current lasres with incorporated
eye-tracking & iris registration systems
3) Under/ Over-correction
- excessive hydration : undercorrection
- desiccation : overcorrection & haze
POSTOPERATIVE
COMPLICATIONS meibomian gland
1) Interface debris – mostly

material – cleaning of interface with BSS

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 – pre-existing dry
eye / blepharitis
- tt frequent lubrication , punctal plugs
6) Diffuse lamellar
keratitis (Sands of
Sahara syn)
- non-infective interface
inflammation
- 1 st week after LASIK
- fine granular sand-like
infiltrate in the interface
periphery
- if not treated  corneal
scarring
 Grade

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

 Grade

II –
Diffuse involvement
– Normal V/A.
- Rx-Add systemic
steroids.
 Grade

III –
Diffuse confluent
granular deposits
- Reduced V/A.No AC
reaction.
- Rx-Same as
above+Antibiotics

 Grade

IV –
Diffuse confluent
granular deposits
+intense central striae.
- Marked Reduced V/A
- Rx-Interface
irrigation + above
 Causes -Proposed

Theory
 Bacterial cell wall endotoxin
 Cleaning solution toxicity
 Talc from gloves
 Miebomian secretions
7) Flap striae & microstriae
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
Microstriae -Flap in
position but fine
wrinkles seen
superficially
-Due to large myopic
ablation
-Rx- Observe.They
resolve
spontaneously
8) Epithelial ingrowth
 Presents 1-3 months
after LASIK.
 Causes-Epithelial cells
trapped under flap
 Risk factors
-Peripheral epithelial
defect
-Poor flap adhesion
-Buttonholed flaps
-Repeat LASIK
 Classification GRADE

1-Faint white line <2mm
from flap edge
 GRADE 2-Opaque cells <2mm from
flap edge with rolled flap edge
 GRADE 3-Grey to white fine opaque
line extending >2mm from flap edge.
 GRADE 4-If ingrowth >2mm from
edge with documented progression
Rx flap lifted  epithelium scraped at
stroma & under flap  repositioned.
Mitomycin-C can be used
9) Infectious keratitis – vision threatening
- M/C organisms – Atypical mycobacteria,
Staphylococci
- Prevention – prophylactic antibiotics
- Pre-treatment of meibomian
gl. disease
- sterile instruments &
techniques
- suction lid specula
10) Keractasia
- Ablation beyond 250 µm of posterior
corneal stroma
- LASIK performed on unrecognized KC
suspects
- tt – RGP lenses, corneal transplant
11) Post op Glaucoma(Pseudo DLK) -Steroid
induced.
12) Vitreoretinal Complications Increased risk of RD due to alteration of
anterior vitreous by suction ring-Risk
0.08%.
LASEK & Epi-LASIK
Corneal surface ablative refractive
procedures
 Anterior stroma of cornea (ant. 1/3
rd)
has stronger interlamellar
connections than post. 2/3 rd .
So surface ablation preserves the
structural integrity better than
LASIK especially in the correction of

LASEK
Creating an epithelial flap with
dilute alcohol (18%) applied for 25-35
seconds & repositioning this flap
after laser ablation
 Plane of cleavage Hemidesmosomal
attachments in the most superficial
part of lamina lucida of BM

Epi-LASIK
Use of a motorized epithelial
separator with oscillating blade, to
mechanically separate a 60-80µ
corneal epithelial flap from stroma &
repositioning this flap after laser
ablation
 Plane of cleavage Not within but
underneath the Basement Membrane

HISTORY
1 st LASEK 1996 by Dr. Azar
 Cimberle & Camellin independently
coined the term LASEK
 Epi-LASIK a recent development in
refractive surgery technology

ADVANTAGES OVER PRK
Greater post-operative comfort
 Faster visual recovery  allows
bilateral simultaneous surgery
 Reduced risk of corneal haze

ADVANTAGES OVER LASIK
Flap related complications are
eliminated in LASEK
 If microkeratome related
complications occur during EpiLASIK, procedure can be easily
converted to PRK & completed
 Absence of corneal lamellar flap in
both procedures, reduces risk of
keractasia

COMPLICATIONS
INTRAOPERATIVE
LASEK related
1) Alcohol leakage
problems:
during surgery
2) Incomplete
flap
epithelial detachment
(insufficient alcohol
exposure)

Epi-LASIK related
Flap-related
- free flap
- incomplete
- buttonholing
EARLY POST-OP COMPLICATIONS
Delayed epithelial healing (3-5 days)
 Pain – resolution of pain accompanies
epithelial closure
 Infiltrates & Infection
- Sterile infiltrates: alcoholpredisposing factor
 Dry eye
 Corneal haze – with increased
ablation depths

Laser Thermo-Keratoplasty
(LTK)







FDA approval Jan 2000
Ho:YAG (Holmium:yttrium-aluminiumgarnet) laser – deliver laser energy to
periphery of cornea
For Hyperopia (0.75 to 2.5 D)
Takes months to stabilize
In time, the effect wears off in a
substantial number of cases
Laser Thermal Keratoplasty
(LTK)
CONDUCTIVE
KERATOPLASTY

Application of low-energy, high
frequency radiofrequency current to
heat & shrink peripheral & paracentral
stromal collagen  resulting in
steepening of central cornea
 Used for hyperopia (1 – 2.25D),
hyperopic astigmatism and
presbyopia
 FDA approved 2002
 Provides better stability than the
previously used procedure Laser



CORNEAL RESPONSE TO HEAT
55 – 58 ˚C  collagen shrinkage
(disruption of
H bonds of tertiary collagen
structure)
65 – 78 ˚C  collagen relaxation
> 78 ˚C  collagen necrosis




Hyperopia
Lower corrections : 8 spots at 6mm optical
zone
& 8 spots at 7mm
optical zone
Greater corrections : 24 spots applied ( 8
additional
(+2 to +2.50D )
spots at 8mm optical
zone)
Even greater corrections : 32 spots
Hyperopic astigmatism
Peripheral heat spots along a single
(flatter) meridian
Conductive Keratoplasty
(CK)
SCLERAL EXPANSION
BANDS






Designed to treat
presbyopia
Not FDA approved
Theory: Presbyopia
is due to
slackening of
fibers attached to
the lens.
Figure : Implanted scleral
expansion band (full circular
band model)
Intrastromal Corneal Ring
Segments
(Intacs)

PMMA arcuate segments placed
within peripheral cornea to correct
myopia
 FDA Approved 1999
 < 3.0 D myopia , < 1.0D
Astigmatism
 Emerging role as an adjunct for
keratoconus & corneal ectasia



1 st generation ICRS : 360˚ ICRS
Current design: 2 PMMA
segments,150˚ arc length



Hexagonal cross section



Fixed inner diam. 6.8 mm
Fixed outer diam. 8.1 mm
Refractive effect directly related to
thickness
INTACS THICKNESS
(mm)
0.25

RECOMMENDED PRESCRIBING RANGE (D)

0.30

-1.75 to -2.25

0.35

-2.38 to -3.00

-1.00 to -1.63
SURGICAL TECHNIQUE
ICRS channel
formation at 2/3 rd
corneal depth,
outside central
optical zone
 Insertion of
segment
 Suturing of entry
site
 Adv
 Reversibility
 Hyperacuitty

PHAKIC INTRAOCULAR
LENSES


Artificial lenses implanted in the anterior
or posterior chamber in the presence of the
natural crystalline lens to correct
refractive errors



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

3 types
Anterior chamber-angle supported PIOL
AC iris-fixated
Posterior chamber PIOL



Early models – PMMA
Newer models – foldable (more safe &
efficacious)


AC angle-supported AC iris-fixated
NuVita (Bausch &
Lomb)
Vivarte (Ciba vision)
Kelman Duet
I-CARE
Acrysof AC

Verisyse/ Artisan
(AMO/Ophtec)
Artiflex/ Veriflex

PC sulcus-supported
Implantable Contact
Lens (ICL)
Phakic Refractive Lens
(PRL)
Sticklens
GENERAL CRITERIA FOR
IMPLANTING PHAKIC IOLs








Age above 18 years
Stable refraction (< 0.5D change for 6 months)
Ammetropia not suitable for Excimer laser
surgery (high powers or thin cornea)
AC depth >= 3.2mm for iris-claw lens
>= 2.5mm for pc PIOLs
Minimum endothelial cell density
> 3500 cells/mm² at 21 yrs age
> 2800 cells/mm² at 31 yrs age
> 2200 cells/mm² at 41 yrs age
> 2000 cells/mm² at 45 yrs age
No other ocular pathology (corneal disorders,
glaucoma, uveitis, cataract)
Indications


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



High Hyperopia
Upto +3.0 D
Ancillary tests

IOL power calculation
AC PIOL
- Power calculation is independent of axial
length of eye
- Depends on : 1)Central corneal curvaturekeratometry (k)
2) ACD
3) Preoperative spherical
equivalent
PC PIOL
- Corneal thickness & axial length also taken
into consideration
AC DIMENSIONS & SIZING OF
PIOL
Most of the complications arise due to
inaccurate sizin of PIOLs
 External measurement from limbus-tolimbus( white-to-white dist.)
 Gives approx estimation of AC diameter
- Measured b/w 3 & 9 o’clock meridians with
calipers
- ORBSCAN
- Videokeratoscopes
- High frequency UBM

Diam of lens = w-w dist + 0.5 to 1.0
mm
(For both angle & sulcus-supported
PIOLs)
AC angle-supported PIOLs
NuVita
Vivarte
AC iris-fixated PIOLs
Artisan/ Verisyse

Most commonly used phakic IOL
Artiflex/ Veriflex
PC sulcus-supported PIOL

Implantable Contact Lens (ICL)
ADVANTAGES
Most stable & predictable refractive
method
 Newer designs – improved safety &
efficacy
 Reversible
 Significant gain of postoperative
BCVA in myopia – reduction in
image minification
 No loss of contrast sensitivity (as
seen in LASIK)

COMPLICATIONS
Haloes & glare
 Pupillary ovalization
( Angle supported PIOLs)
 Endothelial damage
 Elevation of IOP
 Uveits (iris trauma during surgery)
 Cataract (mostly nuclear)

COMPLICATIONS
Anterior chamber inflammation/
pigment dispersion – repeated
traumatic attempts at iris
enclavation (Iris-fixated PIOLs)
 Iris atrophy & IOL dislocation (Irisfixated PIOLs)
 Hyphaema (Iris-fixated PIOLs)
 Decentration / Dislocation into
vitreous cavity (PC PIOLs)

BIOPTICS
Concept of first implanting a phakic
IOL to reduce the amount of myopia,
then fine tuning the residual
correction with LASIK
 I/Cs –extremely high myopia
- high astigmatism
- lens power not available
 Combination has expanded the limits
of refractive surgery

refractive surgeries

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refractive surgeries

  • 1. REFRACTIVE SURGERIES Dr. NEHA PATHAK 2 nd year PG Resident Deptt. of Ophthalmology Govt. Medical College, Kota
  • 2. Eye’s refractive power determined by 3 variables - 1. Power of the cornea 2. Power of the lens 3. Length of the eye EMMETROPIA - Optically normal eye - Image of the object being viewed is focused on retina - Resulting in clear & sharp vision
  • 3. AMMETROPIA – A condition of refractive error - Causes blurred vision as image is not focused on retina 1. Myopia - Near-sightedness Image is focused in front of retina 2. Hyperopia - Far-sightedness - Image is focused behind retina
  • 4. 3. Astigmatism – Refraction varies in different meridia - Rays of light entering eye can’t converge to a point focus but form focal lines 4. Presbyopia – Eye sight of old age - Physiological insufficiency of accomodation leading to progressive fall in near vision - Mechanism : 1. Senile lens hardening
  • 5. PUPIL SIZE & CENTRATION OF REFRACTIVE PROCEDURES    Rays of light from a point source are refracted by the area of cornea overlying the entrance pupil . This area is c/a the corneal optical zone . Entrance pupil - Virtual image of anatomical pupil formed by magnifying effect of the cornea – larger & closer to cornea. Optical zone in a keratorefractive procedure : “The area of central cornea that bears the refractive change caused by the surgery”.
  • 6. FACTORS DETERMINING CENTRATION OF KERATOREFRACTIVE PROCEDURES Foveal photoreceptors orient themselves towards centre of the pupil (StilesCrawford effect), even if entrance pupil becomes eccentric.  Pupillary dilatation under mesopic & scotopic conditions, beyond the edge of the optical zone causes edge glare & haloes => Favour the centration of KR procedures on the 
  • 7. CLASSIFICATION OF REFRACTIVE PROCEDURES REFRACTIVE SURGERIES CORNEA BASED        R.K. PRK LASIK EPILASIK LASEK Conductive Keratoplasty Corneal Inlays and rings LENTICULAR BASED    Clear Lens extraction for myopia Phakic IOL Prelex Clear Lens Extraction with use of Multifocal IOL’s COMBINED(BIOPTICS) • Combination of the two
  • 8. KERATOREFRACTIVE SURGICAL PROCEDURES LOCATION ADDITION SUBTRACTIO N RELAXATION COMPRES SION SUPERFICIAL 1.EPIKERATO PHAKIA 2.SYNTHETIC EPIKERATOP HAKIA 1.PRK 2 LASEK 3.Epi-LASIK ---------- INTRASTOMAL 1.KERATOPHA KIA 2.INTRACORN EAL LENSES 3.PINHOLE APERTURES 1.LASIK 2.WAVEFRONT GUIDED LASIK 3.IntraLASIK (IntraLase) LAMELLAR KERATOPLAST Y PERIPHERAL INTRACORNE AL STROMAL RING WEDGE RESECTION 1.RADIAL KERATOTOMY 2.ARCUATE KERATOTOMY CORNEAL MOLDING 1.THERMOK ERATOPLAS TY. 2.COMPRES SION SUTURES
  • 9. PREOPERATIVE EVALUATION Involves 1)Screening,  2)History taking,  3)Preoperative examination &  4)counselling 
  • 10.  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,EhlerDanlos -Keloids  Systemic Infection-(HIV,TB)  Drugs-Azathioprene,Steroids(Slow wound healing) -Antihypertensives,
  • 11. 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
  • 12. OPHTHALMIC EXAMINATION      VISUAL ACUITY – Distance & Near : with & without correction REFRACTION – Current spectacle correction - Manifest refraction - Cycloplegic refraction (1% cyclopentolate ) EXTERNAL EXAMINATION – Ocular dominance - Ocular motility - Gross external examination SLIT-LAMP EXAMINATION – Fluorescein & vital stain JONES’ BASAL TEAR SECRETION RATE
  • 13. TOPOGRAPHIC ANALYSIS 1) Keratometry (measures Videokeratography central 3 mm corneal curvature) early KC) 2) Computerized (only way to uncover
  • 14. PACHYMETRY - measuring thickness of cornea ULTRASONIC PACHYMETRY Recommendations for minimum bed thickness (250µ) based upon ultrasonic devices 1)
  • 15. 2) ORBSCAN DEVICE - Optical device - Advantage – can provide thickness measurements throughout the cornea
  • 16. EPIKERATOPHAKIA     EPIKERATOPLASTY/ ONLAY LAMELLAR KERATOPLASTY Removal of epithelium from central cornea  peripheral annular keratotomy  lyophilized donor lenticule is reconstituted & sewn into the annular keratotomy site Adv. - simplicity & reversibility Disadv – irregular astigmatism, delayed visual recovery, prolonged epithelial defects. Abandoned procedure now.
  • 17. Radial Keratotomy (RK)    Series of 4-8 deep, radial corneal stromal incisions Weaken the paracentral & peripheral cornea & flatten the central cornea I/C- keratoconus astigmatism
  • 18. LONG-TERM COMPLICATION S - Bullous keratopathy secondary to endothelial cell loss - Low stability of refraction 
  • 19. 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 
  • 20. May be combined with LASIK, PRK, LASEK, Cataract extraction.
  • 21.
  • 22. Cataract surgery - Limbal Relaxing Incisions have gained popularity- more comfortable for patient than arcuate or transverse mid-peripheral incisions
  • 23. PHOTOREFRACTIVE KERATECTOMY First widely used procedure with the excimer laser (1987)
  • 24. 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 
  • 26.      No microkeratome involved No flap created Ultimate visual results similar to LASIK Longer recovery period (> 2 weeks) Complications similar to LASIK; Haze
  • 27. LASIK (Laser-assisted in situ keratomileusis)    Most commonly performed refractive surgery Combines lamellar corneal surgery with accuracy of the excimer laser Excimer laser ablation of corneal stroma beneath a hinged corneal flap that is created with a mechanical femtosecond laser microkeratome
  • 28. 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 1 st 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
  • 29. Types of lasers used Excimer : for corneal stromal ablation Non-Excimer solid state lasers : for flap creation
  • 30. EXCIMER LASERS  Excited   dimer of two atoms -an inert gas(Argon) -a Halide(Fluoride)  releases ultraviolet energy at193nm Reshapes corneal surface by removing anterior stromal tissue Process – Non-thermal Ablative Photodecomposition
  • 31. Laser delivery patterns : 1) Broad-beam lasers - deliver a large diameter beam of laser – starts small & expands as the laser is delivered ADV. Less operative time DISADV. Creation of central islands ( difficulty to maintain uniform consistency over a larger diameter beam)
  • 32. 2) Scanning excimer lasers: - Scanning-slit laser - Flying spot laser Provide smoother ablation than the old broad-beam lasers
  • 33.  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.
  • 34. 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 -15D Hyperopia –upto +6D Astigmatism-upto 6D
  • 35.     CCT such that minimum safe bed thickness left(250-270µ).Post op Corneal thickness should not be <410µ. Extreme keratometric values ( flatter than 41.00 or steeper than 47.00) avoided Videokeratoghic clues to a KC suspect: K value > 47.2 D, Inferior steepening of > 1.4 D, difference of > 1.9 between K values of both eyes Contact lens free period before examination : 3-4 wks for rigid contact lens wearers 2 wks for soft contact lens wearers
  • 36. BASIC MECHANISM     Normal cornea – prolate shape ( greater curvature centrally ) Myopic correction – create an oblate shape by central corneal laser ablation Hyperopia - Excimer laser ablation at midperiphery  steepening of central cornea Mixed astigmatism – 1)Bitoric LASIK technique – flattening the steep meridian with paracentral ablation over the flat meridian 2)Cross-cylinder technique – dividing cylinder power into 2 symmetrical parts – half of the correction is treated on the positive meridian & half on the negative
  • 37. MUNNERLYN EQUATION    Roughly defines the depth of ablation required to achieve a specific amount of correction For 1 D correction  depth of ablation required (in microns) one-third of the square of diameter (in mm) So each spherical equivalent diopter of myopic correction performed at a 6mm optical zone will ablate 12 microns of tissue
  • 38. OPERATIVE PROCEDURE        5mg Diazepam 5-10 min before procedure Verification of entered computer data before starting procedure Topical anasthesia-Proparacaine 0.5%, Lignocaine 4%. Surgical Painting and draping Lid speculum with aspiration Proper centration over pupil & maintenance by the aid of Tracking systems & iris registration C/L eye taped shut to prevent cross-fixation
  • 39. 1 st step - Creation of flap    Corneal marking with ink Adequate placement of suction ring using bimanual technique Suction engagement by foot control
  • 40. Adequate IOP (>65mmHg) which is necessary for the microkeratome to create a pass and resect the corneal flap.  verified by BARRAQUER TONOMETER  confirmed by patient – temporary loss of visualization of fixation light 
  • 41. 2nd step - Resection of corneal flap  Artficial tear drops instilled  MICROKERATOMES 1) Steel 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. 2) Waterjet Keratome -Less debris & collateral damage than blade
  • 42. 3) Laser Keratome (IntraLase) - Solid-state laser 1053 nm wavelength 3 µm spot size- high precision Uses brief Femtosecond laser pulses to cause disruption in a lamellar plane - Needs lower vacuum & any hinge can be made - Can make flaps as thin as 100µ(Sub Bowmans Keratomileusis)
  • 43. - Flap has vertical edges –so reduced epithelial ingrowth. - Steel Microkeratome flap thicker in periphery and thinner in the centre. Not so with Intralase(Planar).
  • 44. 3 rd Step-Delivery of Laser After flap is lifted,assessment of residual corneal bed thickness usin USG pachymetry  laser is applied to the stroma according to the ablation profile calculated by the machine.  Excimer Laser beam is delivered by the following ways depending on the machineBeam Delivery Broad Beam Scanning Slit Beam Flying Spot
  • 45.  Most machines employ a flying spot to deliver laser with the help of incorporated eye tracker or iris registration.
  • 46. 4 th step-Reposition Of the Flap After irrigating interface ,flap reposited  Sweeping movements with a wet cellulose sponge  From the hinge towards the periphery of flap  Adhesion verified – stretching the flap towards gutter  Topical antibiotic, steroid & lubricant instillation  transparent plastic shields
  • 47. WAVEFRONT-GUIDED (CUSTOMIZED) EXCIMER LASER REFRACTIVE SURGERY  To correct higher-order aberrations in addition to lower- order sphero-cylinder corrections - LOWER ORDER Nearsightedness Farsightedness Astigmatism - HIGHER ORDER Spherical aberration Chromatic aberration Diffraction Curvature of field Coma Trefoils Quadrifoils
  • 48.  Higher order aberrations occur in visually significant manner in 1015% of population  Cannot be corrected with spherocylinder lens or conventional laser refractive surgery  Correction – Hard contact lenses - Wavefront-guided customized
  • 49. MEASUREMENT OF WAVEFRONT ABERRATIONS (ABERROMETRY) ABERROMETER OUTGOING ABERROMETERS Analyze outgoing light that emerges From retina & passes through the Optical system of eye Hartmann-Shack Aberrometer (most commonly used) INGOING ABERROMETERS Analyze ingoing light that forms an image on the retina Tscherning Aberrometer Ray Tracing Aberrometer Scanning Slit Refractometer
  • 50. ANALYSIS & DECOMPOSITION OF WAVEFRONT ABERRATIONS INTO COMPONENTS ANALYSIS OF ABERRATIONS ZERNIKE POLYNOMIALS (most commonly used) FOURIER ANALYSIS
  • 51. CUSTOMIZATION OF ABLATION PROFILE TYPES OF CUSTOMIZATION TOPOGRAPHY-GUIDED ABLATION (Conventional laser surgery) WAVEFRONT-GUIDED ABLATION (Customized laser surgery)
  • 52.  Conversion of wavefront measurement data to an ablation profile   Imported to an excimer laser   Precise registration of these patterns on cornea by eye trcking & iris registration technology   Precise wavefront-guided ablation during LASIK is achieved
  • 53. CUSTOMIZED ABLATION PLATFORMS 1) Nidek Advanced Vision EXcimer Laser system    OPD-Scan optical path difference scanning system (combines measurement of corneal topography & aberrometry) Develops customized ablation profile EC-5000CX II excimer
  • 54. 2) VISX S4 CustomVue Platform (Santa Clara, CA)  Wavescan wavefront system – Hartmann-Shack wavefront sensor  STAR S4 excimer laser sytem delivers customized laser ablation
  • 55. 3) Alcon Customized Cornea Platform  LADARWave wavefront sensor ( a HartmannShack eberrometer)  LADARVision system to deliver customized
  • 56. 4)Bausch and Lomb Zyoptix System  Diagnostic part : - Zywave aberrometer – a Hartmann-Shack sensor - ORBSCAN – 3D information about cornea  Truncated Gaussian beam laser – 2 sizes –  2mm – corrects majority of refractive error in short time  1mm – more specific ablation pattern on
  • 57. 5) Allegretto Wavefront-Guided Ablation  Allegretto wave analyzer – Tscherning Aberrometer  Allegretto excimer laser system – high repetition rate spot laser (200Hz) with
  • 58. 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
  • 59. 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
  • 60. 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
  • 61. ABLATION COMPLICATIONS 1) Central islands – small central elevations a) abnormal beam profile (broad beam lasers) b) particulate matter blocking subsequent laser pulses c) increased hydration 2) Decentration – current lasres with incorporated eye-tracking & iris registration systems 3) Under/ Over-correction - excessive hydration : undercorrection - desiccation : overcorrection & haze
  • 62. POSTOPERATIVE COMPLICATIONS meibomian gland 1) Interface debris – mostly material – cleaning of interface with BSS 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
  • 63. 5) Punctate epithelial keratopathy – pre-existing dry eye / blepharitis - tt frequent lubrication , punctal plugs 6) Diffuse lamellar keratitis (Sands of Sahara syn) - non-infective interface inflammation - 1 st week after LASIK - fine granular sand-like infiltrate in the interface periphery - if not treated  corneal scarring
  • 64.  Grade 1Focal involvement - Normal V/A. - Rx Intensive topical steroids.  Grade II – Diffuse involvement – Normal V/A. - Rx-Add systemic steroids.
  • 65.  Grade III – Diffuse confluent granular deposits - Reduced V/A.No AC reaction. - Rx-Same as above+Antibiotics  Grade IV – Diffuse confluent granular deposits +intense central striae. - Marked Reduced V/A - Rx-Interface irrigation + above
  • 66.  Causes -Proposed Theory  Bacterial cell wall endotoxin  Cleaning solution toxicity  Talc from gloves  Miebomian secretions
  • 67. 7) Flap striae & microstriae 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
  • 68. Microstriae -Flap in position but fine wrinkles seen superficially -Due to large myopic ablation -Rx- Observe.They resolve spontaneously
  • 69. 8) Epithelial ingrowth  Presents 1-3 months after LASIK.  Causes-Epithelial cells trapped under flap  Risk factors -Peripheral epithelial defect -Poor flap adhesion -Buttonholed flaps -Repeat LASIK
  • 70.  Classification GRADE 1-Faint white line <2mm from flap edge  GRADE 2-Opaque cells <2mm from flap edge with rolled flap edge  GRADE 3-Grey to white fine opaque line extending >2mm from flap edge.  GRADE 4-If ingrowth >2mm from edge with documented progression Rx flap lifted  epithelium scraped at stroma & under flap  repositioned. Mitomycin-C can be used
  • 71. 9) Infectious keratitis – vision threatening - M/C organisms – Atypical mycobacteria, Staphylococci - Prevention – prophylactic antibiotics - Pre-treatment of meibomian gl. disease - sterile instruments & techniques - suction lid specula
  • 72. 10) Keractasia - Ablation beyond 250 µm of posterior corneal stroma - LASIK performed on unrecognized KC suspects - tt – RGP lenses, corneal transplant 11) Post op Glaucoma(Pseudo DLK) -Steroid induced. 12) Vitreoretinal Complications Increased risk of RD due to alteration of anterior vitreous by suction ring-Risk 0.08%.
  • 73. LASEK & Epi-LASIK Corneal surface ablative refractive procedures  Anterior stroma of cornea (ant. 1/3 rd) has stronger interlamellar connections than post. 2/3 rd . So surface ablation preserves the structural integrity better than LASIK especially in the correction of 
  • 74. LASEK Creating an epithelial flap with dilute alcohol (18%) applied for 25-35 seconds & repositioning this flap after laser ablation  Plane of cleavage Hemidesmosomal attachments in the most superficial part of lamina lucida of BM 
  • 75. Epi-LASIK Use of a motorized epithelial separator with oscillating blade, to mechanically separate a 60-80µ corneal epithelial flap from stroma & repositioning this flap after laser ablation  Plane of cleavage Not within but underneath the Basement Membrane 
  • 76. HISTORY 1 st LASEK 1996 by Dr. Azar  Cimberle & Camellin independently coined the term LASEK  Epi-LASIK a recent development in refractive surgery technology 
  • 77. ADVANTAGES OVER PRK Greater post-operative comfort  Faster visual recovery  allows bilateral simultaneous surgery  Reduced risk of corneal haze 
  • 78. ADVANTAGES OVER LASIK Flap related complications are eliminated in LASEK  If microkeratome related complications occur during EpiLASIK, procedure can be easily converted to PRK & completed  Absence of corneal lamellar flap in both procedures, reduces risk of keractasia 
  • 79. COMPLICATIONS INTRAOPERATIVE LASEK related 1) Alcohol leakage problems: during surgery 2) Incomplete flap epithelial detachment (insufficient alcohol exposure) Epi-LASIK related Flap-related - free flap - incomplete - buttonholing
  • 80. EARLY POST-OP COMPLICATIONS Delayed epithelial healing (3-5 days)  Pain – resolution of pain accompanies epithelial closure  Infiltrates & Infection - Sterile infiltrates: alcoholpredisposing factor  Dry eye  Corneal haze – with increased ablation depths 
  • 81. Laser Thermo-Keratoplasty (LTK)      FDA approval Jan 2000 Ho:YAG (Holmium:yttrium-aluminiumgarnet) laser – deliver laser energy to periphery of cornea For Hyperopia (0.75 to 2.5 D) Takes months to stabilize In time, the effect wears off in a substantial number of cases
  • 83. CONDUCTIVE KERATOPLASTY Application of low-energy, high frequency radiofrequency current to heat & shrink peripheral & paracentral stromal collagen  resulting in steepening of central cornea  Used for hyperopia (1 – 2.25D), hyperopic astigmatism and presbyopia  FDA approved 2002  Provides better stability than the previously used procedure Laser 
  • 84.  CORNEAL RESPONSE TO HEAT 55 – 58 ˚C  collagen shrinkage (disruption of H bonds of tertiary collagen structure) 65 – 78 ˚C  collagen relaxation > 78 ˚C  collagen necrosis
  • 85.   Hyperopia Lower corrections : 8 spots at 6mm optical zone & 8 spots at 7mm optical zone Greater corrections : 24 spots applied ( 8 additional (+2 to +2.50D ) spots at 8mm optical zone) Even greater corrections : 32 spots Hyperopic astigmatism Peripheral heat spots along a single (flatter) meridian
  • 87. SCLERAL EXPANSION BANDS     Designed to treat presbyopia Not FDA approved Theory: Presbyopia is due to slackening of fibers attached to the lens. Figure : Implanted scleral expansion band (full circular band model)
  • 88. Intrastromal Corneal Ring Segments (Intacs) PMMA arcuate segments placed within peripheral cornea to correct myopia  FDA Approved 1999  < 3.0 D myopia , < 1.0D Astigmatism  Emerging role as an adjunct for keratoconus & corneal ectasia 
  • 89.  1 st generation ICRS : 360˚ ICRS Current design: 2 PMMA segments,150˚ arc length  Hexagonal cross section  Fixed inner diam. 6.8 mm Fixed outer diam. 8.1 mm
  • 90. Refractive effect directly related to thickness INTACS THICKNESS (mm) 0.25 RECOMMENDED PRESCRIBING RANGE (D) 0.30 -1.75 to -2.25 0.35 -2.38 to -3.00 -1.00 to -1.63
  • 91.
  • 92. SURGICAL TECHNIQUE ICRS channel formation at 2/3 rd corneal depth, outside central optical zone  Insertion of segment  Suturing of entry site  Adv  Reversibility  Hyperacuitty 
  • 93. PHAKIC INTRAOCULAR LENSES  Artificial lenses implanted in the anterior or posterior chamber in the presence of the natural crystalline lens to correct refractive errors  Intraoperative iridectomy or preoperative Nd:YAG laser iridotomies – necessary to avoid post-op pupillary block glaucoma
  • 94.  3 types Anterior chamber-angle supported PIOL AC iris-fixated Posterior chamber PIOL  Early models – PMMA Newer models – foldable (more safe & efficacious) 
  • 95. AC angle-supported AC iris-fixated NuVita (Bausch & Lomb) Vivarte (Ciba vision) Kelman Duet I-CARE Acrysof AC Verisyse/ Artisan (AMO/Ophtec) Artiflex/ Veriflex PC sulcus-supported Implantable Contact Lens (ICL) Phakic Refractive Lens (PRL) Sticklens
  • 96. GENERAL CRITERIA FOR IMPLANTING PHAKIC IOLs       Age above 18 years Stable refraction (< 0.5D change for 6 months) Ammetropia not suitable for Excimer laser surgery (high powers or thin cornea) AC depth >= 3.2mm for iris-claw lens >= 2.5mm for pc PIOLs Minimum endothelial cell density > 3500 cells/mm² at 21 yrs age > 2800 cells/mm² at 31 yrs age > 2200 cells/mm² at 41 yrs age > 2000 cells/mm² at 45 yrs age No other ocular pathology (corneal disorders, glaucoma, uveitis, cataract)
  • 97. Indications  High Myopia December 2004, FDA approved 1 st PIOL : Verisyse/ Artisan ‘iris-claw’ lens Myopia -5 to -20 D Astigmatism upto 2.5 D December 2005, FDA approved a 2 nd PIOL : Visian ICL(Implantable Contact Lens) Myopia -3 to -20 D Astigmatism upto 2.5 D  High Hyperopia Upto +3.0 D
  • 98. Ancillary tests IOL power calculation AC PIOL - Power calculation is independent of axial length of eye - Depends on : 1)Central corneal curvaturekeratometry (k) 2) ACD 3) Preoperative spherical equivalent PC PIOL - Corneal thickness & axial length also taken into consideration
  • 99. AC DIMENSIONS & SIZING OF PIOL Most of the complications arise due to inaccurate sizin of PIOLs  External measurement from limbus-tolimbus( white-to-white dist.)  Gives approx estimation of AC diameter - Measured b/w 3 & 9 o’clock meridians with calipers - ORBSCAN - Videokeratoscopes - High frequency UBM 
  • 100. Diam of lens = w-w dist + 0.5 to 1.0 mm (For both angle & sulcus-supported PIOLs)
  • 103. AC iris-fixated PIOLs Artisan/ Verisyse Most commonly used phakic IOL
  • 106. ADVANTAGES Most stable & predictable refractive method  Newer designs – improved safety & efficacy  Reversible  Significant gain of postoperative BCVA in myopia – reduction in image minification  No loss of contrast sensitivity (as seen in LASIK) 
  • 107. COMPLICATIONS Haloes & glare  Pupillary ovalization ( Angle supported PIOLs)  Endothelial damage  Elevation of IOP  Uveits (iris trauma during surgery)  Cataract (mostly nuclear) 
  • 108. COMPLICATIONS Anterior chamber inflammation/ pigment dispersion – repeated traumatic attempts at iris enclavation (Iris-fixated PIOLs)  Iris atrophy & IOL dislocation (Irisfixated PIOLs)  Hyphaema (Iris-fixated PIOLs)  Decentration / Dislocation into vitreous cavity (PC PIOLs) 
  • 109. BIOPTICS Concept of first implanting a phakic IOL to reduce the amount of myopia, then fine tuning the residual correction with LASIK  I/Cs –extremely high myopia - high astigmatism - lens power not available  Combination has expanded the limits of refractive surgery 

Editor's Notes

  1. Due to iris trauma during surgery