الفهرس 
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Abstract
Keratoconus is the most common primary ectasia. It usually occurs in the second decade of life and affects both genders and all ethnicities. It is mostly isolated disorder with approximately incidence of 1 per 2000 in general population. The severity of the disease varies from asymptomatic forme frusta conditions to disabling scarring requiring corneal transplantation. Specifically, in asymptomatic conditions, KC may only be detected using sophisticated instrumentation such as videokeratography. Interestingly, keratoconus has familial prevalence of 6-8%.Many studies have been performed for determination of familial pattern of disease which revealed an autosomal dominant and/or recessive inheritance pattern. So, positive family history may be a risk factor for those who ask for refractive surgery. The present study estimated that relatives of keratoconus have a risk 15–67 times higher of developing keratoconus than those who do not have relatives with keratoconus It is interesting to evaluate the topographic pattern of relatives of Egyptian kertoconus patients. This cross section study was performed on first and second degree relatives of previously proved KCN cases by topography and/or clinical examination attended in outpatient clinic of Mansoura university ophthalmic center. Complete slit lamp examination, refraction, and then Corneal topography was performed for all the eyes. The topographic indices for diagnosis of Keratoconus were based on Rabinowitz criteria. In the present study, prevalence of KC in the relative of KC patients is 14.5% and prevalence of suspected KC is 3.6%. It is more in brother than sister and other members of first and second grade of relatives. The high prevalence of the present study was similar to the results of other studies that were conducted in the Middle East which indicate higher prevalence KC than western countries The study included 90 female(65%) and48 male(35%) subjects. Mean age was 30.29. ±13.11 (range 11-65) year old .According to KISA the studied population was divided to normal including 236 eyes and KCN groups including 26eyes (9.6%)which included: male(14 eyes,54% ),and female(12eyes,46%), while suspect KCN was diagnosed in (10eyes,3.7%) which included : male(4eyes,40%), and female(6eyes,60%) Astigmatism was detected in all cases of KCN and suspect KCN group. The mostly astigmatism in normal group was low astigmatism (N=176eyes,74.6%). Axis patterns of astigmatism were : with the rule pattern in39.7%, against the rule in 16.7% and oblique pattern in 43.4%.The against rule pattern astigmatism was 69.2% in KCN and80% in suspect KCN groups(i.e it was the most astigmatism pattern in KCN and suspect KCN group) General topographic patterns of study cases were: round in 120 eyes (44.12%), geographic in 30 eyes (11.03%), and oval in 50 eyes (18.4%). In 38 eyes (14%) astigmatic pattern was symmetrical bow-tie and in the other 34 eyes (12.5%) it was asymmetrical pattern. This study could have been better if we had a bigger sample. The actual study sample may be too small to provide a precise estimate of the pervalance of KC. The sampling of this study was not completely randomized; known cases of KCN were diagnosed before study, which is a weak point.