The effectiveness of soft lenses is limited because the soft lens often takes the same shape of the irregular surface of the cornea. One option is a thicker soft lens which retain more of a rigid shape. There are soft contact lens designs being used for keratoconus, and they can be helpful in mild to moderate cases.
Rigid Gas Permeable (RGP or GP) contact lenses do a better job of correcting the underlying irregular cornea than soft contact lenses because they don't bend or change shape. "Rigid" defines the type of lens. "Gas Permeable" describes the lens material. There are many different RGP lens designs.
The lenses are designed using complex computer models and manufactured on special computerized lathes. The complex geometry of Rose K lenses takes into account the conical shape of the cornea in all stages of the condition.Lenses can be customised to suit each eye and can correct the myopia and astigmatism associated with the condition. Rose K lenses allow the cornea to 'breathe' oxygen directly through the lens material providing excellent health to the eye. The lenses are easy to insert, remove and clean.
This is a two lens combination which requires an RGP lens to be worn on top of a soft lens. The RGP lens provides clear vision and the soft lens provides a more comfortable feel.
For some, this unique single lens design combines the vision benefits of an RGP lens with the comfort of a soft lens. The hybrid lens has an RGP center surrounded by a soft peripheral "skirt".
These lenses have a large diameter that covers the white part of the eye (called the sclera). Scleral lenses have many advantages because of their size. Two major benefits are that they do not fall out and dust or dirt particles cannot get under them during wear. They are also surprisingly comfortable to wear because the edges of the lens rests above and below the eye lid margins so they're hardly noticeable when blinking.
effective in patients intolerent to contact lenses without significant central corneal scarring.Optical out comes are poor with (residual astigmatism and anisometropia) necessitating contact lens corrction for best visual acuity
Ectasia: Dilatation or distension or expansion.
Corneal ectasia: Bulging of cornea.
Irregular conical shape of cornea, secondary to stromal
thinning and protrusion.
Variable rate of progression
-Role of heredity not clearly defined , most without +ve
family history.Only 10%- AD transmission.
Association with systemic conditions
Systemic associations: Down, Turner, Ehlers danlos, Marfan
syndromes, atopy, osteogenesis imperfecta, mitral valve
prolapse and mental retardation.
Ocular assosiations: VKC, blue sclera, aniridia, ectopia lentis,
leber congenital amaurosis, RP, Eye rubbing.
Hormonal changes (proteases,protease inhibitors)
Rigid contact lens wear.
During puberty it’s unilateral, due to progressive myopia and
astigmatism which subsequently becomes irregular.
Due to asymmetrical nature- fellow eye is usually normal
with negligible astigmatism at presentation.
50% of normal fellow eyes progress to keratoconus within
16yrs.Greatest risk- first 6yrs of onset.
-Eye rubbing associated with atopy
-Floppy lid syndrome
Based on severity of curvature:
- Mild <48D
- Moderate 48-54D
- Severe >54D
Based on morphology of the cone:
1) Nipple cones: Small size (5mm)
Apex is central or paracentral &
On slit lamp
Deep stromal stress
Generally vertical, but
they can be oblique
Disappear on pressure
scarring may occur
because of ruptures in
Thickening of the
corneal nerves makes
them more visible.
Yellow brown ring of
Due to deposition of
haemosiderin in the
Which may or may not
the base of the cone
(50% of all cases)
Visualised best with
cobalt blue filter
Corneal scarring occurs
in the advanced the
astigmatism and is
most sensitive method
to detect early
keratoconus and for
thinning - up to 1/5th
cornea thickness can
be seen in the
Sudden loss of vision.
Descements membrane rupture leads to aqueous flow into
Heals within 6-10 weeks and the corneal edema clears
leading to variable amount of stromal scarring.
Tx- for initial stages of acute episodes
-Hypertonic(5%) saline ointment
-Patching or a soft bandage contact lens
Healing (scarring and flattening of cornea)results in
Vediokeratography: by using
1)Placido based system
2) Elevation based system: Uses different
-Optical slit scan
-Side band interferometry
- Restersterography or
Orbscan topography system in one of popular eqipment in this
elevation based system which uses slit scan technology.
Spectacles: In early cases.
Contact lenses: No one lens is best suited for every type of keratoconus.
The needs of each individual are carefully weighed to find the lens that
offers the best combination of visual acuity, comfort and corneal health.
Soft contact lenses
Epikeratoplasty: Patients without corneal scarring.
Keratoplasy: Penetrating or DALK in patients with advanced
disease, especially with significant corneal scarring.
Optical outcomes are poor,
Peripheral corneal thinning disorder in a
crescentic manner, typically involving inferior
Considerably underestimated often
misdiagnosed as keratoconus.
o Equal gender distribution
o Age 20-40yrs at the time of clinical presentation
o Occasionally it may co-exist with keratoconus
-Uncorrected visual acuity is often severely reduced
-Progressive deterioration in uncorrected and
spectacle corrected visual acuity
-Refraction and keratometry show against-the-rule
-Bilateral, slowly progressive crescentic (1-2mm)
band of inferior corneal thinning.
-Extending from 4-8 o’ clock between limbus and
1-2 mm of normal cornea between the limbus and the
area of thinning.
-Acute hydrops are less compared to keratoconus
-Corneal ectasia is most marked just central to the
band of thinning.
-The central cornea is usually of normal thickness
-The degree of thinning is usually severe, resulting
in upto 80% stromal tissue loss.
-The corneal protrusion is more marked- superior
to the area of thinning.
Corneal topography- Shows butterfly pattern, with severe astigmatism
and diffuse steepening of the inferior cornea.
Fail early due to increase in irregular astigmatism.
Early- soft toric
Advanced cases- RGP’s
- Large eccentric penetrating keratoplasty
-Crescentic lamellar keratoplasty
- Wedge resection of diseased tissue
- Intra corneal ring implantation (Intacs)
Thinning and protrusion of the entire corneal
surface (generalised thinning and protrusion)
Non progressive or minimally progressive
-genetically related to keratoconus
-Leber congenital amaurosis
o Onset- At birth
- In contrast to keratoconus cornea develops globular
rather than conical ectasia.
Corneal thinning is generalized.
Cornea is usually transparent.
Corneal diameter is normal.
Acute hydrops are less compared to pellucid
marginal degeneration and keratoconus.
Cornea is more prone to rupture on relatively mild
-Shows generalized steepening
-Congenital glaucoma (Oedematous cornea),
Megalocornea (Not thinned)
-Surgical results are poor, though large diameter
grafting can be attempted
Unilateral thinning of the posterior cornea.
Least common of all ectasias
Developmental, usually non-progressive.
Mild to moderate decrease in visual acuity
Less astigmatism as compared to anterior
- No treatment if abnormality is outside visual
-Glasses can correct refractive error
-Penetrating keratoplasty can be considered in
patients with poor vision.
Ectasia cicatrix (keratectasia):
Ectasia= Bulge forward
Cicatrix= Fibrous scar
There is marked thinning at the site of ulcer.
It bulges forwards even in prescence of
There is no adhesion of iris to cornea.
The cicatrix may become consolidated and
flater later on.
Post-refractive surgery ectasia is a loss of
corneal integrity leading to corneal warpage
that often resembles keratoconus.
It is more likely to occur following LASIK,
radial keratotomy (RK), or astigmatic
keratotomy (AK) surgery.
These types of refractive surgeries are more
likely to cause ectasia because of how they
disrupt the cornea.
Ectatic changes can occur as early as 1 week after LASIK, or
they can be delayed up to several years after the initial
procedure. In many cases, [corneal transplant] is eventually
performed to manage this complication... The continuously
growing popularity of refractive surgery procedures, namely
LASIK, has caused increased concern regarding the serious
complication of keratectasia."
Keratectasia is one of the most feared and dreaded
complications of LASIK. The rate of ectasia after LASIK is
estimated to be about one in 2,000, but this number could
be an underestimate due to underreporting and lack of
long-term followup after LASIK.
Pressure inside the eye called intraocular pressure (IOP),
which pushes on the back surface of the cornea. A normal
healthy cornea easily withstands this force. But after
LASIK, the thinner, weaker cornea may begin to give way
to this pressure, leading to steepening or bulging of the
front surface of the cornea with associated increase in
myopia and irregular astigmatism
Major Risk factors
▪ Keratoconus (KCN)
▪ Forme fruste keratoconus
▪ Pellucid marginal degeneration
Residual stromal bed thickness:
▪ No magic number but most surgeons consider 250 or
300 microns as the minimum
▪ Note: many eyes do fine below these levels and eyes have
developed ectasia above these levels
▪ Measure the stromal bed after the flap is cut
Minor risk factors:
Treatment is the same as keratoconus
Rigid contact lenses
Keratoplasty: DALK or PKP
ECTASIA REGISTRY: A registry for reporting cases of ectasia after
LASIK had its debut recently. The purpose of the registry “is to
identify risk factors that are not currently known and to serve as a
basis for clinical trials in the future,” said Dr. Stulting, who is
directing the project.
There are two anticipated phases to the project. The first phase
will establish a database for submission of information on patients
who developed ectasia after LASIK. These cases will be evaluated
against a control group of LASIK patients who did not develop
ectasia, in an effort to validate known risk factors and discover
new ones. Phase two will include prospective clinical trials of
LASIK in cases involving unproven risk factors.
Ophthalmologists who care for patients with ectasia are
encouraged to participate in the online registry by entering data
on their patients at www.ectasiaregistry.com.
Gina M. Rogers, MD and Kenneth M. Goins, MD
November 11, 2012
Chief Complaint: Decreasing vision after laserassisted in-situ keratomileusis (LASIK)
History of Present Illness: 56-year-old woman.
presentation: post bilateral LASIK for myopia at an
After LASIK- vision in her left eye was great and had
She felt that the vision in her right eye
initially was decent, but never as good as the left eye.
Underwent an enhancement in her right eye
approximately one year after her initial
She felt that the vision did not improve
Over the past three years, the vision in the
right eye had become progressively more
blurred, and could not be improved despite
multiple changes to her eyeglasses
Past Medical History: unremarkable
Past Surgical History: Microkeratome LASIK of both eyes
(OU) in 2001, enhancement in right eye 2002
Right Eye (OD):20/200uncorrected
20/70 with -7.00 + 6.00 x 163
20/30 with scleral contact lens
Left Eye (OS):20/25uncorrected
20/20 with -0.50 sphere
Intraocular Pressure: 14 mm Hg OD and 15 mm Hg OS
Pupils: Symmetric at 4 mm, briskly reactive, no relative
afferent pupillary defect
Confrontation Visual fields: full bilaterally
IRREGULAR CORNEAL CONTOUR WITH
INFERIOR THINNING, FAINT LASIK SCAR,
TRACE NUCLEAR SCLEROSIS
FAINT LASIK SCAR, CONTOUR
TRACE NUCLEAR SCLEROSIS
MARKED INFERIOR STEEPENING
AUTOMATED KERATOMETRY: 60.59 D X
MILD IRREGULAR ASTIGMATISM, WITH
INFERIOR CORNEAL STEEPENING THAT MAY BE
CONSISTENT WITH FORME-FRUSTE
AUTOMATED KERATOMETRY: 42.00 D X 41.25 D
Unfortunately, preoperative topographies and surgical records
were not available. Nonetheless, her right cornea had developed a
very abnormally shaped, ectatic appearance. This patient could
attain improved visual acuity with a scleral contact lens; however,
the contact lens was not tolerable for more than a few hours per
day. Given the severity of the ectasia and corneal topography
findings, Intacs was not indicated. Specular microscopy was
performed to determine endothelial cell density and was found to
be 2746 cells/mm2 in the right eye. The options presented to the
patient were full thickness penetrating keratoplasty (PKP) and
deep anterior lamellar keratoplasty (DALK).[Javadi et al 2010,
Shimazaki et al. 2002] Given the adequate endothelial cell density,
the decision to undergo DALK was made.
DALK surgery was performed using the "big bubble"
technique as described by Anwar.[Anwar et al. 2002a,
2002b] Her surgery was uncomplicated. She developed
steroid induced ocular hypertension that necessitated a
switch of topical steroid formulation as well as transient
treatment with topical ocular anti-hypertensives. Her
pressure remained controlled on the adjusted steroid
regimen and there was no evidence of glaucomatous
damage. The initial selective suture removal was
performed six months post-operatively, and the process
continued until her corneal astigmatism had been
sufficiently reduced. One year after DALK, her
uncorrected visual acuity was remarkably good, at 20/25
Slitlamp photograph of DALK one year post-surgery. Note clarity is excellent
and a moderate amount of sutures are still present.
A comparison of preoperative and postoperative corneal topography shows
the benefit of DALK. Normal prolate corneal morphology has been restored.