corneal ectasias

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.

http://www.kerasoftic.com/files/1713/5393/0584/body_img_eyecare_education_fig1.gif

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)