Keratoconus
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This document provides information on keratoconus, a noninflammatory ectasia of the cornea that causes it to take on a conical shape. It progresses slowly from puberty onward due to a congenital weakness in the cornea that can be exacerbated by eye rubbing, trauma, heredity factors, or conditions like vernal keratoconjunctivitis or Down syndrome. Clinically, it presents with irregular astigmatism and vision defects not fully corrected by glasses. Examination shows thinning and protrusion of the cornea at the apex with striae and opacity. Treatment ranges from glasses and rigid contact lenses to intracorneal ring segments, corneal collagen crosslinking, and keratoplasty procedures for
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Keratoconus
- 3. INTRODUCTION • CONICAL CORNEA • Keratoconus a noninflammatory ectasia of axial part of cornea • Described first by Burchard Mauchart • Usually starts at puberty and progresses slowly
- 4. AETIOLOGY* • Congenital weakness of cornea, though it manifests only after puberty • Secondarily following trauma • Heredity • Eye rubbing • Endocrine anomaly. • With vernal keratoconjunctivitis • Down syndrome
- 5. 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
- 11. 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
- 12. SYMPTOMS • Defective vision due to - progressive myopia - irregular astigmatism which does not improve fully on glasses
- 13. 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
- 14. • 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
- 15. ASSOCIATIONS • OCULAR- ectopia lentis, congenital cataract, aniridia, retinitis pigmentosa, vernal keratoconjunctivitis • SYSTEMIC – marfan’s syndrome, atopy, down’s syndrome, ehlers-danlos syndrome, osteogenesis imperfecta.
- 16. COMPLICATIONS • Acute hydrops – due to rupture of descemts membrane. - characterized by sudden development of corneal edema - marked defective vision, pain, photophobia and lacrimation
- 17. Nipple cone - (<5 mm) Oval cone – (5 to 6 mm) Globus cone – (>6mm) Cone type & position CLASSIFICATION
- 18. Mild <48D Moderate 48-54D Severe >54D Corneal curvature
- 20. SPECTACLE CORRECTION • The patient’s refractive error can often be successfully managed with spectacle in the early stages
- 21. • 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)
- 25. INTACS
- 27. 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
- 29. Lamellar Keratoplasy/ Deep Anterior Lamellar Keratoplasty(DALK)
Editor's Notes
- #5: no one theory fully explains clinical findings No direct evidence but the condition often first develops at the time of puberty and occasionally during pregnancy.
- #6: due to loss of cohesion between collagen fibrils and non collagenous matrix.
- #12: How presentation will benefit audience: Adult learners are more interested in a subject if they know how or why it is important to them. Presenter’s level of expertise in the subject: Briefly state your credentials in this area, or explain why participants should listen to you.
- #13: How presentation will benefit audience: Adult learners are more interested in a subject if they know how or why it is important to them. Presenter’s level of expertise in the subject: Briefly state your credentials in this area, or explain why participants should listen to you.
- #18: small near centre less than 5mm in diameter the most common type, apex of cone is displaced well below midline. a large cone affecting nearly three quarter of corneal surface, more than 6mm in diameter
- #19: (based on keratometry)
- #20: How presentation will benefit audience: Adult learners are more interested in a subject if they know how or why it is important to them. Presenter’s level of expertise in the subject: Briefly state your credentials in this area, or explain why participants should listen to you.
- #26: are surgically inserted through a a small radial incision into a track created within the central cornea stroma
- #28: collagen cross linking within the corneal stroma and so recovers some of its mechanical strength
- #29: -gold standard surgery for keratoconus patients with success rates of more than 90% -keratoconic cornea is replaced by removing the central area of cornea and a full thickness donor corneal button is sutured in its place -corneal trephines between 8-8.5mm are used -second eye is not grafted until the first eye is successfully rehabilitated usually keeping an interval of 12 months.
- #30: a partial thickness corneal transplant -The host cornea is removed upto the depth of posterior stroma and a lamellar donor corneal button is sutured in place technique requires less recovery time, and poses less chance for corneal graft rejection or failure. -This technique is difficult and visual acuity is inferior to that of penetrating keratoplasty In DALK the patients endothelium is retained giving additional structural integrity to post graft cornea. This technique requires less recovery time