corneal ectasias
DESCRIPTION
Many types of corneal ectasiasTRANSCRIPT
Corneal Ectasias
By: Ch.Vineela.
Ectasia: Dilatation or distension or expansion.
http://www.jvascbr.com.br/02-01-02/02-01-02-89/fig03P.jpg
Corneal ectasia: Bulging of cornea.
http://eyewiki.aao.org/File:Keratoconus.jpg
Corneal ectasias include: -Keratoconus -Pellucid marginal corneal
degeneration -Keratoglobus
Keratoconus
Irregular conical shape of cornea, secondary to stromal thinning and protrusion.
Onset: puberty Non inflammatory Bilateral-90% Develops asymmetrical. Variable rate of progression
Aetiology:o -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. Presentation: 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.
Risk factors: -Eye rubbing associated with atopy -Sleap apnea -Floppy lid syndrome
Classification:o Based on severity of curvature: - Mild <48D - Moderate 48-54D - Severe >54D
o Based on morphology of the cone: 1) Nipple cones: Small size (5mm) Apex is central or
paracentral & Displaced inferonasally
2) Oval cones: Larger (5--6 mm) Apex is ellipsoid & Decentered
inferotemporally
3)Globus cones: Largest (>6mm) May involve
75% 0f cornea
Symptoms:
Blurred vision Frequent change in
eye glass prescription " Squinting" in order
to see better Change in the
astigmatic correction of a patient in the 16-25 year-old age range
Distortion rather than blur at both distance and near vision
Double vision Ghost images
Glare Halos Starbursts around lights Itching of the eye/s, vigorous rubbing of eyes Eye strain. Head aches and general eye pain
Signs : Irregular astigmatism
Keratometry shows irregular astigmatism, where the principal meridians are no longer 90 degree apart and the mires cannot be superimposed.
Oil drop reflex
On direct ophthalmoscopy at one foot distance.
Scissoring reflex:
On retinoscopy.
Vogt striae
On slit lamp biomicroscopy
Deep stromal stress lines
Generally vertical, but they can be oblique also
Disappear on pressure with globe.
Sub epithelial scarring
Sub-epithelial corneal scarring may occur because of ruptures in Bowman's membrane. Thickening of the corneal nerves makes them more visible.
Fleischer ring:
Yellow brown ring of pigment
Due to deposition of haemosiderin in the epithelium
Which may or may not completely surround the base of the cone (50% of all cases)
Visualised best with cobalt blue filter
Apical corneal scarring
Corneal scarring occurs in the advanced the advanced cases.
Munson sign
Bulging of lower lid in down gaze
Corneal topography
shows irregular astigmatism and is most sensitive method to detect early keratoconus and for monitoring progression.
Corneal thinning
Significant corneal thinning - up to 1/5th cornea thickness can be seen in the advanced stages.
Acute hydrops:
Sudden loss of vision. Descements membrane rupture leads to aqueous
flow into the cornea. Heals within 6-10 weeks and the corneal edema
clears leading to variable amount of stromal scarring.
Tx- for initial stages of acute episodes -Cycloplegia -Hypertonic(5%) saline ointment -Patching or a soft bandage contact lens Healing (scarring and flattening of cornea)results
in improved VA
Management:
Investigations:
Corneal topography- Keratometer Keratoscope Photokeratoscope Vediokeratography: by using 1)Placido based system 2) Elevation based system: Uses
different methods -Optical slit scan -Side band interferometry - Restersterography or
rasterphotogrammetry Orbscan topography system in one of popular eqipment in this
elevation based system which uses slit scan technology.
Corneal thickness measurement and examination -Pachymetry -Pentacams -Optical coherence tomography -Ultrasound biomicroscopy -Slit lamp examination
Tx
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
Rigid gas permeable lenses
Special contact lenses:
RoseK lenses
Piggy back lenses
Hybrid lenses
Scleral lenses
Epikeratoplasty: Patients without corneal scarring.
Keratoplasy: Penetrating or DALK in patients with advanced disease, especially with significant corneal scarring.
Optical outcomes are poor,
Intra corneal ring segments (Intacs)
Corneal collagen cross linking
Corneal collagen cross linking with + laser
Corneal collagen cross linking with + Topography guided photo refractive keratectomy.
Corneal tranplants
Pellucid marginal degeneration
Peripheral corneal thinning disorder in a crescentic manner, typically involving inferior cornea.
o Bilateralo Asymmetricalo Non-inflammatoryo Perfectly transperento Non-vascularisedo Rare, progressiveo Considerably underestimated often
misdiagnosed as keratoconus.o Equal gender distributiono Age 20-40yrs at the time of clinical presentationo Occasionally it may co-exist with keratoconus
and keratoglobus.
Aetiology: - Idiopathic
Presentation: -4th-5th decades -Uncorrected visual acuity is often severely reduced -Progressive deterioration in uncorrected and
spectacle corrected visual acuity -Refraction and keratometry show against-the-rule
astigmatism.
Signs: -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.
Differential diagnosis: Peripheral corneal melting disorders (eg,
Mooren ulcer) Contact lens-induced warpage Keratoglobus Terrien marginal degeneration.
Tx:
o Spectacles: Fail early due to increase in irregular
astigmatism.o Contact lenses: Early- soft toric Advanced cases- RGP’so Surgical options: - Large eccentric penetrating keratoplasty -Crescentic lamellar keratoplasty - Wedge resection of diseased tissue - Epikeratoplasty - Intra corneal ring implantation (Intacs)
Keratoglobus
Thinning and protrusion of the entire corneal surface (generalised thinning and protrusion)
o Extremely rareo Non progressive or minimally progressiveo Aetiology: -congenital -genetically related to keratoconuso Associations: -Leber congenital amaurosis -Blue sclerao Onset- At birth
Diagnosis:o Signs: - 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 trauma.
Corneal topography: -Shows generalized steepening
Differential diagnosis: -Congenital glaucoma (Oedematous
cornea), Megalocornea (Not thinned) Tx: -Scleral CL’s -Surgical results are poor, though large
diameter grafting can be attempted
Posterior keratoconus
Unilateral thinning of the posterior cornea.
o Least common of all ectasiaso Developmental, usually non-progressive.o Mild to moderate decrease in visual acuity o Less astigmatism as compared to anterior
keratoconus
Tx: - No treatment if abnormality is outside
visual axis -Glasses can correct refractive error -Penetrating keratoplasty can be
considered in patients with poor vision.
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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 normal IOP.
There is no adhesion of iris to cornea.
The cicatrix may become consolidated and flater later on.
Post refractive surgery- corneal ectasias
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 Abnormal topography:▪ 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: Younger patients. Asymmetry Enhancements Myopia
Treatment is the same as keratoconus Rigid contact lenses Intacs Keratoplasty: DALK or PKP Collagen cross-linking
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.
Case of post LASIK ectasia Gina M. Rogers, MD and Kenneth M. Goins, MD November 11, 2012
Chief Complaint: Decreasing vision after laser-assisted in-situ keratomileusis (LASIK)
History of Present Illness: 56-year-old woman. presentation: post bilateral LASIK for myopia at an
outside institution. After LASIK- vision in her left eye was great and had
remained good. 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 surgery.
She felt that the vision did not improve significantly.
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 prescription.
Past Medical History: unremarkable Past Surgical History: Microkeratome LASIK of both
eyes (OU) in 2001, enhancement in right eye 2002 Examination: Visual Acuity 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
Anterior segment
RIGHT EYEIRREGULAR CORNEAL CONTOUR WITH INFERIOR THINNING, FAINT LASIK SCAR,TRACE NUCLEAR SCLEROSIS
LEFT EYEFAINT LASIK SCAR, CONTOUR APPEARS NORMALTRACE NUCLEAR SCLEROSIS
Nidek Corneal Topography
RIGHT EYEMARKED INFERIOR STEEPENING RESEMBLING KERATOCONUSAUTOMATED KERATOMETRY: 60.59 D X 43.95 D
LEFT EYEMILD IRREGULAR ASTIGMATISM, WITH INFERIOR CORNEAL STEEPENING THAT MAY BE CONSISTENT WITH FORME-FRUSTE KERATOCONUSAUTOMATED KERATOMETRY: 42.00 D X 41.25 D
Anterior Segment OCT, Right eye
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.
References:
Kanski- clical ophthalmology 5th and 7th editions.
Diagnostic procedures in opthalmology.
http://keratoconuscanada.org/about-keratoconus/causes-of-keratoconus
http://www.aao.org/publications/eyenet/200801/feature.cfm
http://webeye.ophth.uiowa.edu/eyeforum/cases/158-post-LASIK-ectasia.htm
http://www.lasikcomplications.com/ectasia.htm
http://webeye.ophth.uiowa.edu/eyeforum/cases/158-post-LASIK-ectasia.htm (For case)