KERATOCONUS

LAYA K PILLAI

INTRODUCTION

• CONICAL CORNEA• Keratoconus a noninflammatory ectasia of axial part of cornea

• Described first by Burchard Mauchart• Usually starts at puberty and progresses slowly

AETIOLOGY*

• Congenital weakness of cornea, though it manifests only after puberty• Secondarily following trauma• Heredity• Eye rubbing• Endocrine anomaly.• With vernal keratoconjunctivitis• Down syndrome

PATHOPHYSIOLOGY

• Biomechanical hypothesis proposes keratoconus to result from interlamellar and interfibrillar slippage of collagen within stroma*

• Progressive thinning and ectasia as a result of -defective synthesis of mucopolysaccharide and collagen tissue

CLINICAL FEATURES

• Although can present in any age group, it more commonly affects patients in their late teens or early twenties

• The condition almost always progressive but the rate of progression and severity is variable

• Tends to progress more rapidly in young patients

SYMPTOMS• Defective vision due to - progressive myopia - irregular astigmatism which does not improve fully on glasses

SIGNS

• On ocular examination - Window reflex is distorted. - MUNSON’S SIGN seen• Slit lamp examination - thinning and ectasia of central cornea - opacity at the apex - Fleischer’s ring at base of cone - folds in Descemet’s and bowman’s membranes - very fine, deep stromal striae (VOGT LINES) which disappear with external pressure

• Retinoscopy - SCISSOR REFLEX - irregular astigmatism• Distant direct ophthalmoscopy – annular dark shadow is seen which

separates the central and peripheral areas of cornea (OIL DROPLET REFLEX) • Keratometry – keratometric values are increased• Corneal topography- most sensitive method of detection – FORME FRUSTE

refers to earliest subclinical form of keratoconus detected

ASSOCIATIONS

• OCULAR- ectopia lentis, congenital cataract, aniridia, retinitis pigmentosa, vernal keratoconjunctivitis

• SYSTEMIC – marfan’s syndrome, atopy, down’s syndrome, ehlers-danlos syndrome, osteogenesis imperfecta.

COMPLICATIONS

• Acute hydrops – due to rupture of descemts membrane. - characterized by sudden development of corneal edema - marked defective vision, pain, photophobia and lacrimation

Nipple cone - (<5 mm)

Oval cone – (5 to 6 mm)

Globus cone – (>6mm)

Cone type & position

CLASSIFICATION

Mild <48D

Moderate 48-54D

Severe >54D

Corneal curvatur

e

TREATMENT MODALITIES

SPECTACLE CORRECTION

• The patient’s refractive error can often be successfully managed with spectacle in the early stages

• Usually a rigid gas permeable contact lens improve vision in early cases• In moderate cases, a specially designed scleral contact lens (ROSE-K) is useful• INTACS, the intracorneal ring segment, are useful• Corneal collagen cross linking with riboflavin and UV-A rays may slow the

progression• Keratoplasty required in later stages -Deep lamellar keratoplasty (DALK) -Penetrating keratoplasty (PK)

INTACS

CORNEAL COLLAGEN CROSS LINKING WITH RIBOFLAVIN

• This treatment have been shown to slow down or arrest the progression of keratoconus and in some cases reverse it

• The need to keratoplasty thus might be significantly reduced

• Clinical trials are continuing and the technique is definitely showing promise in treating early cases

Penetrating keratoplasty

Lamellar Keratoplasy/Deep Anterior Lamellar Keratoplasty(DALK)