LASER SUBEPITHELIAL KERATOMILEUSIS
Introduced by Massimo Camellin in 1999.
LASEK combines advantages and features of both PRK
It involves removal of an epithelial flap ( chemically
loosened with alcohol) before ablating the corneal stroma
with Excimer laser.
SURGICAL PARAMETERS AND TECHNIQUE
LASEK resembles PRK more than does LASIK, so
surgical considerations are similar, except following
Epithelium removal in LASEK is in form of hinged flap.
Trephining: an epithelial trephine (8.5-10.5mm in size) is
placed on the center of anaesthetized cornea.
By gentle pressure on the cornea the trephine cuts the
epithelium, sparing the underlying stroma and 4mm
SURGICAL PARAMETERS AND TECHNIQUE
Alcohol treatment: After epithelial trephining, a similar
sized alcohol well is centered on the cornea.
The well is filled with 20% ethyl alcohol and kept in
position for 60 secs.
The alcohol is then removed with a cellulose sponge and
the well is taken off the cornea, and epithelium is washed
Separation of epithelial flap: after waiting for a minute
(during which the alcohol treated epithelium is loosened
from the underlying bowman’s membrane), a microhole is
used to pick up the epithelium rom the edges of trephine
SURGICAL PARAMETERS AND TECHNIQUE
Corneal stromal ablation: is then carried out to correct
refractive error( as described in PRK)
Reposition of epithelial flap: after ablation the corneal
surface is washed thoroughly and scrapped to rid of the
debris and condensed plume.
Then the epithelial flap is carefully rolled back with the
help of an irrigating cannula.
Bandage contact lens: is then applied over the cornea for
LASEK WITH MITOMYCIN -C
Some surgeons use 0.02% Mitomycin C for 30 secs
after corneal ablation and through wash with BSS before
reposting the epithelial flap.
Mitomycin C is useful in curtailing the fibroblastic activity
and thereby reducing and delaying the chances of
corneal haze-more so when treating high myopia.
Post Operative Mx is similar to that in PRK and LASIK.
Advantages of LASEK over PRK:
Less postoperative pain.
Early recovery and less postoperative haze due to improved epithelial
ADVANTAGES OVER LASIK:
Corneal Ectasia is less likely as residual corneal bed thickness is more.
Flap related complications like button hole, partial flap, free caps, lost
flap, flap wrinkling and epithelial down growth are less known.
Additional correction of myopia upto 5 D more than LASIK is
possible, as another 90u of corneal stroma is available for ablation.
In thin cornea, LASEK is better option than LASIK
Increase in high order aberrations, noted with LASIK is excluded with
Postoperative dry eye chances are less as the corneal nerves are not
severed as with LASIK.
Large zone treatment is possible with LASEK. In LASIK the flap size is
a restricting factor to the size of the treatment zone.
LASEK VS LASIK : PRESENT STATUS
Presently LASEK is a good alternative to LASIK where
the latter is a handicap E.g in patients with myopia >8D
and in those with thin cornea.
However, LASEK is not preferred over LASIK because of
Postoperative pain is more
Delayed recovery, i.e vision remains blurred for 7-10 days
Corneal haze similar to PRK is definitely encountered on
long term follow up.
EPIPOLIS LASER IN SITU KERATOMILEUSIS (
Epi- Lasik is just like LASEK except that in it the epithelial
flap is created with the help of an ‘Epikeratome’ and thus
the epithelial cells are not damaged by chemical toxicity of
SURGICAL TECHNIQUES AND POSTOPERATIVE
Surgical technique and postoperative management of a
case of epi- LASIK is same as that of LASEK except the
technique of creation of epithelial flap which is described
Creation of epithelial flap: made with help of epikeratome.
Epikeratome travels across the eye more slowly than the
This gives better control over the separation.
Epikeratome: has a blunt blade or separator made of
either plastic or stainless steel which cleaves or pushes
away a much more smoother epithelial flap.
Advantages of epi-LASIK:
Advantages of epi- LASIK over PRK and LASIK : are same
as that of LASEK.
Advantages of epi-LASIK over LASEK:
The use of epikeratome eliminates the need for the alcohol
used in LASEK.
Since the alcohol is toxic to epithelial cells, avoiding
alcohol application in epi-LASIK results in:
Less corneal haze
C LASIK DEFINITION
Custom ablation is an ablation pattern that attempts to
optimize eye’s optical system using a variety of
spherical, cylindrical, aspherical & asymmetrical Rx based
on individual eye’s optic & anatomy as well as the pt needs.
The exact assessment of individual eye’s optic is made by
Corneal Topography & Aberrometry.
The customized ablation highlights that it selectively
corrects the inherent aberrations of each individual eye.
TYPES OF CUSTOMIZED ABLATION
guided ablation: takes
care of ocular aberration
detected by corneal
topography & treats the
irregularities as an
integrated part of laser
ablation: treats the
aberrations of the entire
human optical system
that are measured by a
variety of wavefront
Although the human eye is an optical marvel, yet it suffers many
deviations from being an ideal optical system.
All forms of deviations (refractive errors) are basically
Aberrations can be grouped as:
1. LOWER ORDER ABERRATIONS: include
myopia, hypermetropia and regular astigmatism.
2. HIGHER ORDER ABERRATIONS: are subtle deviations from
ideal optical system.
These include spherical aberrations, chromatic
aberrations, coma, decentering, oblique aberration and centering.
The higher order aberrations do not lend themselves to easy
Thus, the higher order aberrations limit the potential visual
acquity of the eye.
CUSTOM LASER IN SITU KERATOMILEUSIS
LASIK corrects only low order aberrations such as
spherical and cylindrical refractive errors.
The high order aberrations which effect the quality of
vision but not significantly the Snellen visual acuity are not
corrected by standard LASIK procedure.
Rather, the conventional laser Rx on the cornea increases
high order aberrations, especially at night when the pupil
The aberrations are increased because the normal cornea
is prolate in shape( steeper in the centre), but it becomes
oblate ( steeper in the periphery) after conventional
CUSTOM LASER IN SITU KERATOMILEUSIS
These aberrations are probably the reason for
deterioration of visual performance in some eyes after
conventional photorefractive procedures.
Besides this, there are cases with irregular astigmatism
following eg. Penetrating corneal grafts, penetrating
injuries or peripheral corneal scar, which are not amenable
to conventional ablation procedures.
Custom LASIK tackle the above listed problems.
C LASIK PROCEDURE
1. MEASUREENT OF THE OPTICAL ABERRATION OF
Corneal topography and wavefront aberrometry: systems
have been developed to measure all the optical
aberrations of the eye.
These measuring devices have the ability to measure
refraction to submicron level of about 0.01 D.
A wave print of the eye is created.
This information is used to prepare a customized laser
C LASIK PROCEDURE CONTD..
2. LINKING THE MEASURED OPTICAL ABERRATION TO
THE LASER MACHINE:
The software is available that combines all the measured
data which is then downloaded into a floppy disk and
inserted into the laser machine computer.
3. LASER ABLATION:
Customized ablation requires a flexible laser system that
can deliver a small spot( less than 1.0-2.0mm) or use an
erodible mask customized to a very subtle level, and an
excellent eye tracking system or an eye immobilizing
1. High quality vision: C- LASIK provides a high quality
vision which is comparatively free from night
glares, halos and has improved contrast sensitivity.
2. Supervision: human eye has much better potential
visual acuity of about 6/2 to 6/1.5
This is greatly reduced by diffraction of light and the high
order aberration of the eye.
There fore, by customized ablation, which takes care of
the aberrations of the eye, it is possible to achieve
supervision to the tune of 6/4 or 6/3.
3. Less invasive technique:
Lesser amount of tissue ablation is require to achieve
the given effects.
4. Can correct irregular astigmatism
Commercially available systems for customized ablation
Nidek NAVEX LASIK system with optical path
The IntraLase ultrafast femtosecond laser is the first
bladeless laser technology for performing LASIK.
Step One: Corneal flap creation by means of
The laser uses an infrared beam of light to precisely
separate tissue through a process called Photodisruption.
In this process, the focused laser pulses divide material at
the molecular level without the transfer of heat or impact
to the surrounding tissue.
IntraLase creates the flap from below the surface of the
cornea, using an "inside-out" process.
The silent beam of laser light is focused to a precise point
within the stroma (central layer of the cornea) where each
pulse of the laser creates a tiny 2- to 3-micron bubble of
carbon dioxide and water vapor.
Thousands of these microscopic bubbles are precisely
positioned to define the flap's dimensions, as well as the
location of the hinge.
Bubbles are then stacked along the edge of the flap up to the
corneal surface to complete the flap.
The process from start to finish takes approximately 22
In Step Two:
Flap is opened, so that an excimer laser can be used
Flap is then returned to its original position where it seals
IntraLase spares more of the sensory nerves in the cornea
responsible for reflex tearing than the manual
keratome, beneficial in dry eye pt as compared to LASIK.
IntraLase also places less pressure on your eye than the
Aside from comfort considerations, this creates greater
safety for patients who are glaucoma suspects.
IntraLase can also allow some of those who were not
previously considered candidates due to thinner
corneas, the ability to have the procedure.
100% blade-free – combines all the latest all-laser
100% customised – tailored to the unique
characteristics of your eyes.
Incredibly safe – one of the safest medical procedures
in the world.
Highly effective – the majority of patients experience
20/20 vision or better.
Fast & virtually painless – it only takes a few seconds to
correct each eye.
Suitable for almost everyone – more people treated
than ever before
RELEX AND SMILE
Traditional laser surgery involves cutting a flap off the front
of the cornea or pushing the outer cells of the eye to one
side and using a laser to change the shape of the cornea.
With ReLEx there is no flap cut.
Possible only with the VisuMax Laser from Carl Zeiss
FLEx -Femtosecond Lenticule Extraction
SMILE -Small Incision Lenticule Extraction
THE RELEX PROCEDURE: HOW IT WORKS
ReLEx mainly consists in the creating micropulses
beneath the surface of the cornea, or lamella, a disc-
shaped piece of corneal tissue.
This represents a considerable difference between ReLEx
In fact, the lenticule incision, performed with the
femtosecond laser, is conducted at the same time of the
creation of a corneal flap from which the surgeon is able to
take the lenticule.
Finally, after the lenticule is removed from the surface of
the cornea, the flap is repositioned
RELEX AND SMILE
“Several great advances come from not having to create
a flap or disturb the front of the cornea; the level of
correction can be much higher without weakening the
People who are contact lens intolerant can now be
candidates as there is little or no dry eye after ReLEx.
CORNEAL RESHAPING WITHOUT ABLATION
Excimer laser performs photoablation.
The photo ablation rate increases linearly with fluence [flux]
(defined as the total number of particles that intersect a unit
area in a specific time interval of interest, and has units of m–2
), beyond a certain threshold.
Excimer Laser fluence and photoablation rate gets influenced
by various factors:
corneal hydration levels, humidity levels, the presence of
organic vapour's, the depth of ablation
This results in a scatter, especially for the treatment of high
REFLEX AND SMILE
A refractive lenticule is created in the intact cornea and
removed through a small incision. No need for point-by-
point ablation as with an excimer laser. No flap.
Reflex uses cutting instead of ablation
A binary process instead of linear.
Much less influence of any external factors reflected in
the tremendous accuracy achieved.
Results are especially interesting for high myopia, a
group in which excimer lasers don’t fare as well
INDUCTION OF ABERRATIONS
Excimer lasers suffer from peripheral fluence loss
Fresnel reflection losses at a high angle of incidence
Increase in spot size in the periphery
Leads to an increase in spherical aberrations
Minimized by newer ablation profiles
However, with ReLEx, this problem is essentially not there.
Should lead to less induction of spherical aberration
SO WHEN IS AN EXCIMER NEEDED
Wavefront Guided Procedures (< 5% of a normal
Retreatments (< 1% in ReLEx procedures)
Hyperopia (Latest results of ReLEx for Hyperopiaare quite
BENEFITS OF REFLEX OVER OTHER REF SX
No risk of flap displacements (There is a cap. There is no
With no flap displacement even after trauma, this is a better
option for those involved in close- contact sports or jobs with
chances of injuries.
Small Incision results in minimal cutting of corneal nerves.
Less dry eyes, smaller reduction in corneal sensitivity.
Less discomfort for the patient for a smaller period
Possible better biomechanical stability relative to Femto-
ReLEx is faster to perform than LASIK as only one laser is
ReLEx may be potentially reversible, while LASIK is
An 80% lesser cut means that the chances of complications like
infections, ingrowth of the epithelium, etc. are drastically
BENEFITS OF REFLEX OVER OTHER REF SX…
Suction applied during surgery is restricted to the cornea. This
ensures that side effects seen commonly with other techniques
like sub-conjunctival hemorrhage (bleeding under the
conjunctiva) is significantly lesser.
The FBS experienced by patients at the time of corneal healing
after the operation is reduced to 2-3 hours as compared to 4-5
hours in LASIK and 2-3 days in PRK.
It does not produce the smell of burnt tissue as seen with an
excimer laser and there is no blackout of vision during the
procedure as there is no occlusion of the central artery.
D. MISCELLANEOUS CORNEAL REFRACTIVE
PROCEDURES FOR MYOPIA
Miscellaneous corneal refractive procedures
Intacorneal contact lenses
Intrastromal corneal ring segments (INTACS)
Gel injectable adjustable keratoplasty
Is an non surgical reversible method of moulding
the cornea with over night wear of unique rigid gas
permeable contact lenses to correct myopia.
1. Meticulous refraction: to ascertain the exact amount of
spherical and cylindrical lens to correct the myopia.
2. Corneal topography: to map the shape of anterior
surface of cornea.
3. Calculations of parameter of corrective contact lenses:
are then made from the observation of corneal topograph
and exact amount of refractive error to be reserved.
4. Manufacturing of special contact lenses: which produce
the desired effect for reshaping of the patient’s cornea is
5. Wearing schedule: after desired correction s made, the
lenses may only be needed to be worn a few hours a day
for about 3 days a week to keep the cornea in shape
necessary to see clearly without glasses and without CL.
Is useful at any age with spherical prescription less
than -4 D and astigmatism less than -1.5 d.
This a great alternative for:
Those who are too young to consider LASIK of any
age below 18 yrs.
Refractive error has not been stabilized.
Those youngsters and teenagers who are involved
in sports where wearing contact lenses or glasses
might be limiting their sports activity
1. Non surgical method
2. Available for most people, even younger
3. Freedom from constant corrective lens wear
4. Better vision improvement
5. Reversible method
1. Longer result time
2. Not a permanent solution
3. Higher startup cost than regular contact lenses or
4. Currently only for myopia
Are implanted into the peripheral cornea, producing a
vaulting effect that flattens the central cornea and
corrects myopia of upto 3 D
Features of Intracorneal rings include:
Made of PMMA
Outer dia 8.1mm
Inner dia 6.7 mm
Arc length 150º
Positioning hole dia 0.28mm
Rings cross section – hexagonal
Each package consists contains two rings- right and left
Thickness – available in five different thickness inserts
0.25, 0.30, 0.35,0.4 and 0.45mm
INDICATIONS OF INTACS
Myopia: pt with low degree myopia -1.O –3.5 D who
are willing to get rid of glasses.
Other indications: keratoconus, pellucid marginal
degeration, and post LASIK corneal ectasia.
Collagen vascular ds
Autoimmune or immunodeficiency ds
Pregnant or nursing women
Presence of ocular conditions such as recurrent
corneal erosion syndrome
Corneal dystrophy that may predispose the pt to
Marking of geometric centre of cornea is done with help
of 11mm zone marker.
Corneal thickness is measured at the site of the planned
An incision, 1.2mm in length , is made with a sharp
diamond blade at 12 o’ clock position.
Corneal tunnels(pockets) are then created at
approximately 2/3rd stromal depth using pocketing hook.
Insertion of Intacs: is then done maintaing a space of
2mm between their ends at 6 o clock and space of 1.5mm
btwn their ends and the edge of the incision at 12o clock
Intracorneal ring. After a peripheral circular lamellar dissection, two polymethyl
methacrylate ring segments of predetermined diameter and thickness are inserted. The
midperipheral anterior lamellae are lifted focally by the ring segments, which results in a
compensatory flattening of the central anterior lamellae and hence a decrease in the
refractive power of the cornea.
Antibiotic/steroid combination: QID *2-3 wks
Lubricating artificial tear: QID* 4 wks
Advantages of Intacs over LASIK include:
Maintain normal positive aspherity.
Preserve corneal stroma
Rapid visual recovery
Safety and cost effective
Disadvantage of Intacs:
Non effective in myopia >4 D
Complications like under/ over
correction, neovascularization, extrusion and visual side
INTRACORNEAL CONTACT LENSES
Have also been tried but never became popular
GEL INJECTABLE ADJUSTABLE KERATOPLASTY
Is being tried in pt with -1 to -4 D myopia.
A non-toxic semisolid gel is injected in paracentral
stroma after making a tunnel as described in Intacs
Potential advantages include ease of manipulation
, adjustability and reversibility
INTRAOCULAR REFRACTIVE SURGERIES FOR
A. Refractive lens exchange (extraction of clear
Extraction of clear lens had been advocated for
myopia -16 t0 -18D, especially in U/L cases.
Zero power IOL is better than no IOL , since it not only
retards PCO but also minimizes the incidence of RD.
Refractive errors with associated lens opacities
, specially in presbyopic age.
High refractive error, myopia of >10 D and hyperopia of >
5 D are ideal for RLE.
Retinal ds that are potentially vision imparing.
Occupational night drivers.
INTRAOCULAR REFRACTIVE SURGERIES FOR
B. Phakic refractive lenses:
IOL of appropriate power is implanted inside the
eye, without touching the normal crystalline lens, thus
without disturbing the accommodation.
Safe & predictable
LASIK can be performed for residual refractive error
Low to moderate myopia: -1 to 10 D
LASIK/ C-LASIK: -1 TO -10D
Epi-LASIK : Thin cornea & -6 TO -10 D
INTACS: -1 TO -3 D
ORTHOKERATOLOGY: -1 TO -3 D below 18 yrs of
High myopia:-7 to -10 D
RLE (preferred after 40 yrs of age)