Keratoconus

opthalmology

1. Keratoconus LAYA K PILLAI

2. Introduction CONICAL CORNEA Keratoconus a noninflammatory ectasia of axial part of cornea Described first by Burchard Mauchart Usually starts at puberty and progresses slowly

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

4. 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

5. 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

6. Symptoms Defective vision due to - progressive myopia - irregular astigmatism which does not improve fully on glasses

7. S igns 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

8. 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

9. Associations OCULAR- ectopia lentis , congenital cataract, aniridia , retinitis pigmentosa , vernal keratoconjunctivitis SYSTEMIC – marfan’s syndrome, atopy, down’s syndrome, ehlers-danlos syndrome, osteogenesis imperfecta.

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

11. Nipple cone - (<5 mm) Oval cone – (5 to 6 mm) Globus cone – (>6mm) Cone type & position CLASSIFICATION

12. Mild <48D Moderate 48-54D Severe >54D Corneal curvature

13. Treatment Modalities

14. Spectacle Correction The patient’s refractive error can often be successfully managed with spectacle in the early stages

15. 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)

16. INTACS

17. 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

18. Penetrating keratoplasty

19. Lamellar Keratoplasy / Deep Anterior Lamellar Keratoplasty (DALK )