Keratoconus

keratoconus

1. ISRA SCHOOL OF OPTOMETRY 3 RD YEAR BsVs ZAMEER SADHAYO KERATOCONUS

2. Keratoconus is a condition in which cornea assumes a conical shape because of thinning and protrusion. Cellular infiltration and vascularization do not occur. It is usually b/l and, although it involves central two-thirds of cornea, apex of cone is usually centered just below visual axis. This results in mild to marked impairment of visual function. KERATOCONUS

3. They are keratoconus , pellucid marginal degeneration , keratoglobus , and posterior keratoconus . first three disorders may actually represent variations in phenotypic expression of same pathogenetic mechanism. Corneal thinning is a hallmark of these ectatic diseases. area of maximal thinning, relative to location of maximal corneal protrusion, is helpful in differentiating these conditions . KERATOCONUS

4. PMD is a b / l , non-inflammatory , peripheral corneal thinning disorder characterized by a peripheral band of thinning of the inferior cornea. The cornea in and adjacent to the thinned area is ectatic.The etiology of PMD has not been clearly established, but collagen abnormalities, as seen in KC, have been reported. Patients usually are aged 20–40 years at the time of clinical presentation Pellucid Marginal Degeneration (PMD) & Pellucid-like Keratoconus (PLK)

5. It is a generalized thinning of cornea . thinning is marked at limbus , extending circumferentially for 360°; this makes it different from the globus morphological pattern of the KC .• The whole cornea protrudes , in contrast to the regional thinning seen in KC and the inferior paralimbal thinning in PMD. Keratoglobus

6. Keratoglobus . A generalized bulging and thinning of the cornea

7. Forme Fruste Keratoconus (FFKC) is a subclinical disease and is not a variant of KC. Although clinicians use many other terms such as mild KC, early KC, and subclinical KC , their exact meanings and applications are less certain. These terms are not universally accepted. The diagnosis of KC is a clinical one that is aided by topography , while the diagnosis of FFKC is topographic. Forme Fruste Keratoconus

8. FFKC is a completely normal cornea with neither clinical nor topographical risk factors, but this cornea is able to develop KC when treated by laser. The fellow eye may be keratoconic or there may be a family history of KC TWO OPINIONS REGARDING THE DEFINITION

9. FFKC is an abnormal cornea. Corneal topography or corneal hysteresis or both are abnormal; i.e ., there are risk factors but the case is still not a clinically obvious KC. TWO OPINIONS REGARDING THE DEFINITION

10. A KERATOCONUS B PMD C KERATOGLOBUS D POST KERATOCONUS

11. KC occurs with increased frequency with systemic and ocular conditions: 1. Systemic disorders : Down’s syndrome, Turner syndrome, Ehlers- Dunlos syndrome, Marfan syndrome,atopy , osteogenesis imperfecta, and mitral valve prolapse . 2. Ocular associations : Vernal disease, retinitis pigmentosa , blue sclera, aniridia , and ectopia lentis KERATOCONUS

12. Munson’s sign : When the patient is asked to look downward toward the floor , a V-shaped profile of the lower lid margin can be seen . Moderate-to severe KC tends to produce Munson’s sign, while mild cases will not produce this sign . Rizzuti’s sign : This sign is observed by seeing a light on the nasal anterior sclera when the light is directed into the cornea from the temporal direction Clinical Findings

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14. scissoring effect of the retinal reflex seen with retinoscopy is highly diagnostic of KC (and of all forms of irregular astigmatism). It is best seen when the pupils are dilated. Unlike Munson’s sign, scissoring effect is considered to be sensitive to even mild forms of KC Retinoscopy Signs

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16. Focal thinning : focal thinning occurs at the cone apex,which is usually located inferior to the center of cornea ; in pellucid marginal degeneration (PMD), this focal thinning is located in the lower third of the cornea. Fleischer’s ring : It is due to accumulation of ferritin particles in corneal basal epithelial cells. It encircles the base of the cone . Slit Lamp Biomicroscopy Signs

17. As cornea continues to thin and bulge out,“ stretch marks ” may develop in form of thin,bright lines located deep in the stroma adjacent to Descemets ’ membrane called Vogt’s striae . Vogt’s striae are a sign of corneal stretching and protrusion. When cornea is depressed, Vogt’s striae often disappear. These striae are sometimes called stress lines. Vogt’s striae , hydrops cornea, and corneal scaring

18. Anterior stromal scars may develop due to continuous protrusion of the cornea. These scars may be small or large . The size and location of the scars determines its impact on visual function. If stretching becomes excessive, the cornea may eventually tear in the Descemets ’ membrane leading to fluid accumulation within the stroma and therefore to hydrops cornea . Contin ……..

19. This intense stromal edema often results in an acutely blurred vision since the tears often occur centrally. When the endothelium migrates to cover the tear,edema resolves and a posterior scar may form. Tears can occur in corneal periphery which may have minimal impact on vision Corneal hydrops

20. CORNEAL HYDROPS