Keratoconus and management

Disease
 Keratoconus is a degenerative non-inflammatory disease of the
cornea where the central or paracentral cornea undergoes
progressive thinning and steepening causing irregular
astigmatism.

Etiology
 Etiology is unknown.
 However, it is associated with atopy, Down’s Syndrome, Leber’s
congenital amaurosis, and Ehler’s Danlos/connective disorders.
 The hereditary pattern is neither prominent nor predictable, but
positive family histories have been reported.
 The most common presentation of keratoconus is as a sporadic
disorder, in which only a significant minority of patients exhibit a
family history with autosomal dominant or recessive transmission
 The incidence of keratoconus if often reported to be 1 in 2000
people.

Dr. Mohd Najmussadiq Khan 11/7/2012 2

Risk Factors
 Eye rubbing, associated with atopy
 Sleep apnea
 Floppy Lid Syndrome


 Based on severity of curvature
◦ Mild : less than 45.00D
◦ Moderate : 45.00 to 52.00D
◦ Advanced : 52.00 to 62.00D
◦ Severe : more than 62.00D

 Based on shape:
◦ Nipple cones (Small size 5mm )
◦ Oval cones (larger (5-6mm) ellipsoid)
◦ Globus cones (Largest >6mm ,may involve over 75%
of cornea. )


 Retinitis Pigmentosa
 Leber’s Congenital Amaurosis
 Microcornea
 Aniridia
 Corneal Degeneration
 Congenital Cataract
 Ectopia lentis
 Lenticonus
 Macular coloboma
 Retinal dysplasia
 Floppy eyelid syndrome


 Down’s syndrome
 Ehlers-Danlos syndrome
 Osteogenesis Imperfecta
 Mitral valve prolapsed


General Pathology --Keratoconus can show the
following pathologic findings
 Deposition of iron in the basal epithelial cells,
forming the Fleischer ring—a pigmented ring
that results from the accumulation of ferritin
particles in the cytoplasm of epithelial cells
and widened intercellular spaces.
 Breaks in Bowman's membrane, filled with cells,
collagen, and PAS-positive material.


 thinning of stroma and overlying epithelium
 abnormal keratocyte morphology, and
endothelial polymorphism
 folds or breaks in Descemet’s membrane
(Vogts striae)
 variable amounts of diffuse corneal scarring.


Pathophysiology
 Histopathology studies demonstrate breaks in or
complete absence of Bowman’s layer, collagen
disorganization, scarring and thinning.
 The etiology of these changes is not known,
though some suspect changes in enzymes that
lead to breakdown of collagen in the cornea.
 While a genetic predisposition to keratoconus is
suggested, a specific gene has not been
identified.


Biochemical abnormalities:--
 Studies in patients with keratoconus have
demonstrated an increased activity by
proteases that breakdown the collagen cross-
linkages in the corneal stroma.
 There is a simultaneous reduced expression
of protease inhibitors.
 The ratio of keratin sulfate to dermatan
sulfate is altered in the stromal matrix when
compared to normal corneas.
 Patients with keratoconus have also shown
enzymatic changes in the epithelium with
increased expression of lysosomal and
proteolytic enzymes.

Primary prevention
 No preventive strategy has been proven
effective to date.
 Some feel that eye rubbing or pressure (e.g.
sleeping with the hand against the eye) can
cause and/or lead to progression of
keratoconus, so patients should be informed
not to rub the eyes.
 In some patients, avoidance of allergens may
help decrease eye irritation and therefore
decrease eye rubbing.


Diagnosis
 Diagnosis can be made by slit-lamp examination
and observation of central or inferior corneal
thinning.
 Computerized videokeratography is also useful in
detecting early keratoconus and allows following its
progression.
 Ultrasound pachymetry can also be used to measure
the thinnest zone on the cornea.
 New algorithms using computerized
videokeratopgraphy have been devised which now
allow the detection of subclinical or suspected
keratoconus.
 These devices may allow better screening of
patients for prospective refractive surgery.


History
 The majority of cases of keratoconus are bilateral,
and often asymmetric.
 The less affected eye may show a high amount of
astigmatism or mild steepening.
 Onset is typically in early adolescence and
progresses into the mid-20’s and 30’s. However,
cases may begin much earlier or later in life.
 There is variable progression for each individual.
 There is often a history of frequent changes in eye
glasses which do not adequately correct vision.
 Another common progression is from soft
contact lenses, to Toric or astigmatism correcting
contact lens, to rigid gas permeable contact lenes.

Physical examination
 A thorough and complete eye exam should be
performed on any patient suspected of having
keratoconus.

 The general health of the eye should be assessed
and appropriate ancillary tests should be done to
assess corneal curvature, astigmatism and
thickness.

 The best potential vision should also be evaluated.
Many of the potential exam components are listed
below:

 Proper history, including change in eye glass
prescription, decreased vision, history of eye
rubbing, medical problems, allergies, sleep patterns


 Assessment of relevant aspects of the patient’s mental and
physical status.

 Measurement of best corrected visual acuity with spectacles and
hard or gas permeaable contact lenses (with refraction when
indicated)

 Measurement of pinhole visual acuity

 External examination (lids, lashes, lacrimal apparatus, orbit)

 Examination of ocular alignment and motility
 Assessment of pupillary function

 Measurement of intraocular pressure (IOP)

 Slit-lamp biomicroscopy of the anterior segment

 Dilated examination of the lens, macula, peripheral retina, optic
nerve, and vitreous

 Keratomety/Computerized Topography//Ultrasound Pachymetry

Symptoms
 Progressively poor vision not easily corrected
with eye glasses.
Clinical diagnosis
 Diagnosis is made based on history of
changing refraction, poor best spectacle
corrected vision, abnormalities in
keratometry, corneal topography and corneal
thinning.


 Asymmetric refractive error with high or
progressive astigmatism
 Keratometry showing high astigmatism and
irregularity (axis that do not add to 180 degrees)
 Scissoring of the red reflex on ophthalmoscopy
or retinoscopy.
 Inferior steepening, skewed axis, or elevated
keratometry values on K reading and
computerized corneal topography


 Corneal thinning, especially in inferior cornea.
Maximum corneal thinning corresponds to the site of
maximum steepening or prominence.
 Rizutti’s sign or a conical reflection on nasal cornea
when a penlight is shone from the temporal side
 Fleischer ring, an iron deposit often present within
the epithelium around the base of the cone. It is
brown in color and best visualized with a cobalt blue
filter
 Vogt’s striae, fine, roughly vertically parallel striations
in the stroma. These generally disappear with firm
pressure applied over the eyeball and re-appear
when pressure is discontinued.


 Munson’s sign, a protrusion of the lower eyelid in
down gaze.
 Superficial scarring • Break’s in Bowman’s
membrane

 Acute hydrop’s, a condition where a break in
Descemet’s membrane allows aqueous into the
stoma causing severe corneal thickening,
decreased vision and pain.

 Stromal scarring after resolution of acute
hydrops, which paradoxically may improve vision
in some cases by changing corneal curvature and
reducing the irregular astigmatism.

 Differentiation is made between a “quiet” type
of keratoconus (“forme fruste”) and
progressive keratoconus.
 “Forme fruste” occurs 10 times more often
than progressive keratoconus.
 Normally it produces no symptoms and has
only to be observed.
 If the condition remains stable, there is no
need for treatment.


 Progressive keratoconus is aggressive and can
begin at a very early age.
 With progression of the disease, correction of
visual acuity with glasses becomes more difficult
because protrusion of the cornea develops
unevenly.
 Hard contact lenses are a good solution because
they put pressure on the cornea, thus correcting
irregularities.


Diagnostic procedures
 • Ophthalmic history, including family eye history,
heritable disease, history of allergies, etc

 • Slit-lamp examination

 • Hard or gas permeable contact lens trial because good
vision with lenses eliminates other sources of poor vision,
including amploypia

 • Measurement of K values

 • Ultrasound Pachymetry

 • Computerized corneal topography


Laboratory test--Assessment of heritable diseases
including
 • Down’s Syndrome
 • Leber’s congenital amaurosis
 • Ehlers Danlos/connective disorder.
 • Other medical conditions including sleep apnea

Differential diagnosis
 • Keratoconus
 . Pellucid marginal degeneration
 • Keratoglobus
 • Contact lens induced corneal warpage
 • Coneal Ectasia post excimer laser treatment


 In 1963, scientists found that the initial
changes of KC were related to degradation
(break down) of the cornea s basement
membrane.
 They found that over time, a cascade of events
occurred, leading to alterations in the layers of
the cornea and resulting in the thinning of the
stromal layer.
 This weakened the structural integrity of the
cornea and in turn resulted in a bulging, cone-
like distortion of the normally spherical cornea.


 Investigators found that the enzyme activities
of the KC corneas were increased compared to
normal corneas.
 In addition, there was a significant reduction of
inhibitors for these enzymes.
 The cornea is responsible for approximately
80% of the absorption of ultraviolet B (UVB)
light that enters the eye.
 UV light generates free oxygen radicals, high
energy molecules, which if unchecked, can
damage tissue.

Typically, the free radicals are removed from
the cornea via antioxidants (such as superoxide
dismutase, catalase and glutathione reductase).

Those that are not removed undergo reactions
that form aldehydes, which can be destructive
to the tissue


 Normally, the cornea protects itself from these
aldehydes with an enzyme called aldehyde
dehydrogenase (ALDH) which detoxifies these
aldehydes.
 ALDH is a major protein within the cornea.
(Approximately 78% of the ALDH within the eye
is found in the cornea.).
 In the KC cornea there is decreased activity of
ALDH enzyme.


These peroxynitrites are also harmful to tissues and can
be identified by using antibodies to nitrotyrosine.

KC corneas have an increased amount of nitroytrosine
staining compared to normal corneas

This increased staining in KC corneas suggests that they
have additional destructive substances in the tissue.


 Normally, the human cornea has very little
apoptosis occurring.
 Dr. Wilson demonstrated that KC corneas
have apoptosis occurring in the anterior
stroma and epithelium, especially in the areas
of breaks in Bowman's layer.


 KC corneas produce a unique enzyme that is not
found in normal corneas or corneas with other
diseases.
 This enzyme is called leukocyte common
antigen related protein (LAR).
 LAR in KC corneas also supports the notion of
apoptosis in KC corneas because other
investigators have shown in other systems that
LAR expression plays a role in apoptosis.


 The goal of future research studies is to
understand the biochemical and molecular
changes and possible genetic influences that
occur in KC corneas.
 Intervention at one of these steps might be
the key factor needed to block the
progression of keratoconus.


General treatment --The goal of treatment is
primarily to provide functional visual acutiy.
More recently attention has been directed to
halting changes in the corrneal shape.

 Initially, spcetacles or soft toric contact lenses in
mild cases can be used.


 Patients with very mild disease may initially
be corrected with glasses or soft contact
lenses.
 However the vast majority of patients need
rigid contact lenses for adequate vision
correction.
 The very latest contact lens for treating
keratoconus is the “synergize hybrid contact
lens” which is rigid in the middle and soft on
the edges.

 Needed in the majority of cases to neutralize the
irregular corneal astigmatism.
 It resurfaces the irregular cornea & the
intervening fluid and corrects the irregular
astigmatism to provide good quality of vision.
 However the disadvantage with these lenses is
that they have standard lens design with fixed
optical zones and do not give an ideal fit in
patients with keratoconus
 The majority of patients that can wear hard or
gas-permeable contact lenses have a dramatic
improvement in their vision.

 Many patients find their contact lenses
uncomfortable and can only tolerate their
contact lenses for a short period of time.
 The reason is that the cornea steepens and
rubs against the lens causing an abrasion and
light sensitivity . 
 Another reason is patients with keratoconus
often have very dry eye and as the eye dries
out there is no lubricating barrier between
the lens and the cornea contributing to the
patient being uncomfortable.

 RoseK-- The Rose-k lenses are made with
complex geometry to fit any type of cone. The
optical zone is reduced to snugly fit the cone &
the peripheral curve is computer designed to fit
the rest of the irregular cornea.


 piggy back lens-- they are known as piggy
back because a RGP Lens is fitted on top of a
soft contact lens. These lenses provide
excellent comfort and good vision.


 Scleral Contact Lenses: They are made of a
special polymer called Itaflurocon. They
characteristically vault over the cornea and
limbus and are supported entirely by the
sclera. The fluid lens smoothens the irregular
cornea and provides good vision. It also
prevents desiccation due to its very high
oxygen permeability. The small pores on the
lens provide adequate exchange of tears. The
disadvantage with these lenses is that they
are difficult to use. They are large lenses
which are cumbersome to the patients.

 Boston Scleral Contact lenses (BSLP): BSLP
lenses are made of Flurosilicone Acrylate
Polmers with DK values of 87 and 130. Its
diameter ranges from15.5mm to 20mm. The
space created over the cornea is filled with
non-preserved, buffered sterile saline. The
limitation to the use of these lenses is that the
fitting process is skill intensive and time
consuming.


Those patients that become contact lens
intolerant or do not have acceptable vision,
typically from central scaring, can proceed to
surgical alternatives


Medical therapy—for acute corneal hydrops
involves
 a cycloplegic agent
 sodium chloride 5% ointment or eye drop
 Lubricating eye drop
 Steroid drops can be used if the eye is
congested
 a pressure patch
 After the pressure patch is removed patients
may still need to continue sodium chloride
drops or ointment for several weeks to months.
 Patients are advised to avoid vigorous eye
rubbing

 It takes 3 - 4 months for the corneal edema to
resolve, following which a standard full
thickness keratoplasty is required to restore
corneal clarity and visual improvement.
 It this situation lamellar surgery is not
recommended
 Thermokeratoplasty has been tried and
believed to shrinkage of the collagen with
resultant flattening of the hydrops which helps
in early healing of the ruptured DM.


 Patients are usually followed on a 6-month to
yearly basis to monitor the progression of the
corneal thinning, steepening, the resultant
visual changes, and to re-evaluate contact
lens fit and care.
 Patients with hydrops are seen more
frequently until it resolves.


 When patients become intolerant or no longer
benefit from contact lenses, surgery is the next
option. Surgical options can include: INTACS,
Anterior lamellar keratoplasty, penetrating
keratoplasty.
 Non- FDA approved treatments, which typically have
less evidence based information available on safety
and efficacy, include use of UV/riboflavin collagen
cross-linking of the cornea to stiffen the cornea and
possibly prevent progressive changes in shape. This
treatment has also be experimentally combined with
excimer laser treatment, conductive keratoplasty,
and/or INTACS.
 Some surgeons will use phakic IOLs to address high
myopia and some of the asitigmatism.


 The most promising technology for treating
Keratoconus called collagen crosslinking
(CXL) with UVA is currently being introduced
 It is undergoing Phase 1 FDA clinical trials in
the United States.
 It has been demonstrated to be safe and
effective if performed, with the epithelium
removed, and has the potential to stop the
progression of Keratoconus.


 This treatment is recommended for
individuals with progressive Keratoconus or
Ectasia following LASIK to stabilize the
cornea.
 It can be performed with our without INTACS.


CORNEAL COLLAGEN CROSS-LINKING (C3R/CXL):
 The basic problem in keratoconus is the weakness of
the cross links which act as anchors between the
collagen fibrils.
 UV-A irradiance of the cornea after sensitization with
riboflavin, augments these cross-links, and hence
recovers some of the corneal mechanical strength in
keratoconus.
 This treatment modality stabilizes the collagen scaffold
and increases the stiffness of the cornea against the
action of proteolytic enzymes.
 Riboflavin/UVA light causes increase in the corneal
stiffness of the anterior 200-250 μm.
 Deeper structures like the lens and endothelium do not
get damaged.
 The progression of keratoconus or keratectasia can be
stopped.

 This results in cross linking of the collagen
fibres of the cornea, thereby increasing
its physical strength by up to 300%.
 Thus further progression of keratoconus can
be arrested, and in 15 -20% cases regression
has also been noted.
 Longest follow-up duration following this
treatment is for 7 years.


 The top layer of the cornea is removed under local
anesthesia.
 Vitamin drops are soaked into the cornea until they
penetrate the entire corneal and evidence of
penetration into the anterior chamber of the eye is
demonstrated by slit-lamp evaluation.
 Once this is confirmed the patient’s eye is put under a
specialized lamp, which emits UV A light at a
predetermined wavelength for approximately 30
minutes.
 During this process the cross links, which link the
fibers of the cornea, are increased thereby stiffening
the whole cornea.
 A bandage contact lens is then put on the eye and
patients are given antibiotics and anti-inflammatory
drops and follow up on a regular basis with their
physicians for several months.

 During the post-operative period flurometholone
and artificial tears are applied for a period of one
month.
 In the pilot study done on 23 eyes and followed up
to 4 years Wollensak et al found a mean reduction
in steepening of 2.01 D.
 Other investigators such as caporossi et al and
Krumeich et al reported a similar result.
 The improvement in vision after cross-linking is
caused by a decrease in astigmatism and corneal
curvature as well as topographical homogenization
of the cornea as a result of the increased rigidity in
the cross- linked cornea.
 In addition tolerance to contact lenses improved.
 Cross-linking is a practical outpatient treatment,
which is minimally invasive and cost-effective.


 A method for flattening the cornea that is too
steep and making a patient more contact lens
tolerant is the insertion of INTACS into the
cornea.
 This procedure is good for patients who are
contact lens intolerant and who want to avoid
a corneal transplant and whose K readings
are not in excess of 58 Diopters.
 (INTACS ) have been approved for the
treatment of mild to moderate keratoconus in
patients who are contact lens intolerant.


 In these cases, patients must have a clear central
cornea and a corneal thickness of > 450 microns
where the segments are inserted, approximately
at 7 mm optical zone.
 Intrastromal corneal ring segments (Intacs
Addition Technology Inc) have crescent shaped
two 150-degree PMMA segments that are
surgically placed in the peripheral cornea at two-
thirds corneal depth.
 Intacs comes in thickness ranging from 0.25 to
0.45 mm in 0.05 mm increments.
 Intacs correct the myopia and irregular
astigmatism by producing a mechanical flattening
of the central cone.

 The advantage of INTACS is that they require no
removal of corneal tissue, no intraocular
incision, and leave the central cornea
untouched.
 Most patients will need spectacles and/or
contact lenses post-operatively for best vision,
but will have flatter corneas and easier use of
lenses.
 If a patient does not gain the expected results,
the INTACS can be removed and then other
surgical options can be considered


 Femtosecond laser technology allows
realization with very high accuracy of
individualized shape and size of corneal tunnel
depending on the surgical need.
 Intrastromal cuts from the inner to the outer
parts of the cornea can be performed easily.
 During surgery, stress to the cornea is
minimal, because only moderate pressure is
exerted on the eye.
 The risk of infection is significantly reduced.


 Kera rings are tiny plastic semicircular rings
surgically implanted into the cornea to flatten
the corneal surface and improve vision.
 Inserts can improve contact lens wear in most
patients.
 They are not suitable for all patients with
keratoconus.
 Implantation does not affect the central optic
zone, does not involve the removal of any
tissue, and can be reversed if vision changes.


Imagine your cornea as
a tent with a curved top.
If you push out the sides
of the tent, the top
flattens.
Similarly, when Kera
rings are placed in the
sides of the cornea, they
flatten it.


Combined KERARINGS insertion and CXL can be performed safely in one or
two sessions. However, the same-session procedure appears to be more
effective regarding the improvement in the corneal shape. Br J Ophthalmol.
2011 Jan;95(1):37-41. Epub 2010 Jun 28.


 Laser may now be used to treat keratoconus.
 The technique is similar to the Lasek laser done for
short sight etc, but uses a cornea topographer to
guide the laser.
 The laser reduces the keratoconic protrusion,
significantly improving vision.
 When controlled by a topographer only a few microns
of cornea need be removed, greatly enhancing safety.
 The technique is effective for mild-to-moderate
keratoconus.
 To stabilize the cornea after laser, collagen cross
linking is done.
 Only the most sophisticated lasers, such as the Alcon
Wave light EX500 excimer laser can be used

 It is the newest procedure under investigation for the
treatment of keratoconus.
 It is non-incisional and reshapes the cornea without
removing any tissue.
 It is currently under clinical investigation in Europe for
treating myopia and keratoconus.
 It involves the delivery of a single low energy
microwave pulse lasting less than one second to the
cornea.
 Energy is applied to the cornea using a dielectrically
shielded microwave emitter which contacts the
epithelial surface.
 Through capacitive coupling, the single pulse raises the
temperature of the selected region of corneal stroma to
approximately 65°C, forming a doughnut-shaped area
of collagen shrinkage in the upper 150 microns of the
stroma.

 The lesion created during Keraflex is intended
to flatten the central cornea both to decrease
the cone in keratoconus and to achieve myopic
correction.
 In order to improve the stability of the cornea
with Keraflex, Keraflex KXL includes focal
corneal collagen crosslinking.
 After the actual Keraflex procedure, riboflavin
drops are administered over the treatment
area, a mask is applied to protect the central
and peripheral areas of the cornea, and
ultraviolet light is admistered to crosslink the
collagen.

 Corneal Transplants are the only option for
patients who have scarring in the center of
the cornea or who are contact lens intolerant
because their corneas are too steep.
 The results of corneal transplants are
excellent in keratoconus patients with an over
97% success rate.
 Patients can have LASIK or PRK on their
transplants and become relatively
independent of glasses or contact lenses.
 Recently the Femtosecond Laser was
approved for performing Corneal Transplants


 It involves replacement of the central anterior
cornea, leaving the patient’s endothelium
intact.
 The advantages are that the risk of endothelial
graft rejection is eliminated, and there is less
risk of traumatic rupture of the globe in the
incision, since the endothelium and
Descemet’s and some stroma are left intact,
and faster visual rehabilitation.


 There are several techniques utilized including,
deep anterior lamellar keratoplasty (DALK) and
big bubble keratoplasty(BBK) to remove the
anterior stroma, while leaving Descemet’s layer
and endothelium untouched.
 However, the procedures can be technically
challenging requiring conversion to a penetrating
keratoplasty
 Post-operatively there is the possibility of
interface haze leading to a decrease in BCVA
 It is not clear if astigmatism is better treated with
anterior vs penetrating keratoplasty.


 In DALK the bottom layer of the cornea is
spared this results in less chance of rejection.
 It should be remembered however that in
some instances the separation of the bottom
layers of the cornea and the upper parts might
be uneven which would result in poorer visual
outcomes.


Descemets exposed

DALK(deepanteriorlamellarkeratoplasty


 It has a high success rate and is the standard
surgical treatment with a long track record of
safety and efficacy.
 Risks of this procedure include infection and
cornea rejection and risk of traumatic rupture at
wound margin.
 Many patients after PK may still need hard or gas-
permeable contact lenses due to residual irregular
astigmatism
 Any type of refractive procedure is considered a
contraindication in keratoconic patients due to the
unpredictability of the outcome and risk of leading
to increased and unstable irregular astigmatism.


10

 Following any corneal surgical procedure,
patients need to be followed to complete visual
rehabilitation.
 Most patients still require vision correction with
spectacles or contact lenses, and often hard or
gas permeable lenses are required if high levels
of astigmatism are present.
 All surgical patients need to be followed to
ensure wound healing, evaluation for infection,
suture removal and other routine eye care, such
as testing for glaucoma, cataracts and retinal
disease.
 Graft rejection can occur after penetrating
keratoplasty, requiring prompt diagnosis and
treatment to ensure graft survival.
10

Complications
 Infection
 poor wound healing
 cornea transplant rejection
 corneal neovascularization
 Glare
 irregular astigmatism
 high refractive error

10

Prognosis
 The prognosis for penetrating keratoplasty in a
keratoconic patient is excellent, with most patients
able to return to an active lifestyle and the pursuit
of personal goals.
 Intrastromal corneal ring segments (such as Intacs)
can provide long-term success for patients with
keratoconus, but this is typically in conjunction with
contact lens use, and some may ultimately require
corneal transplant to reach their goals of visual
rehabilitation. "Progression" of keratoconus, even
after corneal surgery, has been reported, but it is
not clear how common or to what extent this can
occur
10

 The donor stromal lenticule was created
using the femtosecond laser (Intralase).
 The diameter of the lamellar cut was 9 mm.
 The laser parameters were set to cut the first
lamellar interface at a depth of 400 μm
posterior to the epithelial surface.
 A side cut was then performed creating a
tapered edge to the lenticule.
 Then, a second superficial lamellar cut was
made at a depth of 150 μm posterior to the
epithelial surface.
 This produced a 250-μm donor corneal
lamellar disc. 10

 Next, a stromal pocket was formed in the host
cornea at a depth of 250 μm using the Intralase.
 The diameter of the pocket was 9.5 mm, with a
3.0-mm exit incision at the 12 o’clock position
 The patient was then taken to the operating
room where prepared with povidone-iodine 10%
solution
 The donor lamellar lenticule was folded and
inserted into the host stromal pocket through the
anterior incision.
 The donor lenticule was centered and smoothed
with a cyclodialysis spatula.
 The wound was closed with a single 10-0 nylon
suture.
10

Keratoconus and management

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Keratoconus and management