الفهرس 
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Abstract
Keratoconus has remained a scientific enigma. Despite more than one-hundred years of exhaustive study little progress has been made in understanding its cause. Clinically, it is a frustrating disease for both the patient and doctor. When severe, it can result in crushing disability for the patient and strong psychological effects. The unknown course and uncertain prognosis also make management of these challenging1.
Keratoconus is a non inflammatory ectatic dystrophy characterized by progressive thinning, steepening, and apical conic protrusion of the cornea. These changes in corneal shape induce irregular astigmatism and myopic shift, causing gradual impairment of vision1 .
Keratoconus, classically, has its onset at puberty and progresses until the third to fourth decade of life, when it usually arrests. The natural course of the disorder is difficult to determine because usually the corneal changes begin before the first examination of the patient. Typically at the age of puberty, the presumably normal cornea of the patient begins to thin out and protrude, resulting in irregular astigmatism. The severity of the disorder at the time when progression stops may range from very mild irregular astigmatism to severe thinning 2.
A genetic predisposition to keratoconus has been observed with the disease reported with increased incidence in some family groups and reports of concord¬ance in identical twins 3.
The frequency of occurrence in first and second degree family members of affected individ¬uals is variable, although it is known to be considerably higher than that in the general population. Studies have estimated between 6 per cent and 19 per cent of close family members may be affected 3.