Transcript 49-REFRACTIVE-SURGERIES-(2)

REFRACTIVE SURGERIES
Dr.Jyoti Shetty
Medical Director,
Bangalore West Lions
Superspeciality Eye Hospital
CLASSIFICATION
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
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

Types of lasers usedExcimer-Excited dimer of two atoms
-an inert gas(Argon)
-Halide(Fluoride)
which releases ultraviolet energy at193nm
for corneal ablation


Non-Excimer solid state lasers

210nm Q switched diode pumped laser (laser
off)
213 nm Q switched diode pumped
laser(Pulsar)

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 -12D
Hyperopia –upto +6D
Astigmatism-upto 7D


CCT such that minimum safe bed
thickness left(250-270µ).Post op
Corneal thickness should not be
<410µ.
Cornea not too flat or steep.<36D
or>49D(Poor Optics).
CONTRAINDICATIONS

Systemic factors







Poorly controlled IDDM
Pregnancy/lactation
Autoimmune / connective tissue disorders(RA,SLE,PAN
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)
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)
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

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.



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


Pachymetry -For CCT
(Ultrasound/Optical)
Contrast Sensitivity testing for preoperative baseline.
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
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.

2nd step-Resection of corneal flap
Microkeratome
Femtosecond Laser
(Intralase)

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.

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)


Flap has vertical edges –so reduced
epithelial ingrowth.
Microkeratome flap thicker in periphery
and thinner in the centre.Not so with
Intralase(Planar).

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 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.

4th step-Reposition Of the Flap

After irrigating interface ,flap reposited
Adhesion test-Striae test
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
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.
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
-Don’t violatecorneal topography
diagnosis of forme-fruste keratoconus
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
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)
COMPLICATIONS OF LASIK

Flap
Complications

Button Hole-If
K>50D,due to
central corneal
buckling.
.


Irregular thin flapInadequate
suction/old blade
Short Flap-Hinge
encroaches on
visual axis-Due to
jamming of
microkeratome with
hair/FB
SHORT FLAP

Free Cap-Due to
flat pre –op
K(<38D).

.Flap undulationsMacrostriae-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

Microstriae-Flap in
position but fine
wrinkles seen
superficially
-Due to large
myopic ablation
-RxObserve.They
resolve
spontaneously
MICROSTRIAE

Bleeding during flap cutting due to
corneal neovascularization in contact
lens users

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
Grade 1Focal involvement Normal V/A.
Rx Intensive
topical steroids.


II – Diffuse
involvement –
Normal V/A.
Rx-Add
systemic steroids.


III – Diffuse confluent
granular depositsReduced V/A.No AC
reaction.
Rx-Same as
above+Antibiotics
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

Infection-Potential complication as any
surgical procedure

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

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—Lift flap and
remove the sheets of epithelium.Can use
MMC.
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.


LASEK-Camellins Technique

20% absolute alcohol used for 20-35s. To
raise epithelial flap.
Flap reposited after ablation


EPILASIK- Epithelial keratome used to
lift epithelial flap of about 60-80µ thick.
Epithelial keratomes use
- PMMA blades
-Metal Epithelial Separator
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.
5mm
6
7

Drawbacks


Regression and retreatment in 100%
cases after 6 months.
Induced cylinder >1D reported in many
cases.
Usually done in one eye—Many have
intolerance to monovision.
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.
AcuSof Corneal inlay
Phakic IOLs


An intra-ocular lens is placed inside the
eye in front of the patient’s natural lens.
These are available in three types
1.
2.
3.
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).
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 >2000cells/cumm
No other ocular pathology
Contraindications









Myopia other than axial myopia
Corneal dystrophy/ Endothelial cell count
<2000cells/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
Angle supported anterior chamber phakic IOLs – Rigid lenses
IOL
NuVita MA20
ZSAL-4
Phakic6
Bausch & Lomb
Morcher
M&C
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
12 -13.5mm
12.0/13.5mm
12 – 14mm
- 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
Company
Prev. model
Haptic + optic
Diopters (D)
________
??
Angle supported anterior chamber phakic IOLs – Foldable
IOls
IOL
Vivarte
I CARE
Kelman Duet
The Vision
Membrane
Company
Ciba vision
Corneal
(france)
Material
Hydrophillic
acrylic (RI =
1.47)
HEMA 26%
Optic- Silicone Silicone
Haptic PMMA
Optic
5.5 mm
5.75 mm
5.5 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 -8.0 to -20.0 D
injectable lens
Vision
membrane
technologies
7.0 mm
Anterior Chamber Phakic IOL
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 patient’s refraction changes.
Iris fixated phakic IOL – Verisyse
Phakic IOL


Most commonly used phakic IOL
One-piece design
Verisyse Phakic IOL
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
Veriflex (artiflex)

Foldable iris claw lens. It is a
modification of Verisyse (Artisan)
phakic IOl.
Posterior chamber lenses

These phakic IOLs are placed in the
posterior chamber between the iris &
the crystalline lens. These are
1.
2.
Starr ICL
Cibavision PRL
STAAR ICL

The STAAR Collamer ICL and the TORIC
ICL are posterior chamber phakic intraocular
lenses. Made of Collamer, STARR’s
proprietary collagen copolymer
(colagen/HEMA), the lens rests behind the
iris in the ciliary sulcus.
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.
Complications




ICL decentration
Pupillary block
Pigment dispersion
Subcapsular cataract
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.
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.