الفهرس 
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Abstract
Astigmatism is an optical refractive error, which develops when the shape of the eye’s refractive components, primarily the cornea and crystalline lens, deviates -#102;-#114;-#111;-#109; being rotationally symmetric. There is wide prevalence of astigmatism worldwide, and estimates commonly exceed 30% of the population depending on the astigmatism power threshold adopted in each study (0.5 or 1.0 diopter).Keratoconus is a non-inflammatory, ectatic corneal dis-#111;-#114;-#100;-#101;-#114; that manifests later on in the disease process and involves central corneal thinning, corneal protrusion and progressive, irregular astigmatism.In keratoconus, the progressive corneal thinning and cone formation result not only in myopia but also in asymmetrical irregular astigmatism, which is a major cause of the impaired visual acuity (VA)). Early signs of KC can occur on the posterior corneal surface . A rotating Scheimpflug camera enables measurements of both anterior and posterior corneal surfaces . Such Scheimpflug measurements can be centered either on the corneal apex or on the pupil centre , and different measurement diameters can be chosen . A larger measurement zone diameter has been shown to render higher corneal irregularity in normal corneas and a more negative spherical equivalent in KC . Our study was conducted on patients attending outpatient clinic of Mansoura ophthalmology center , Faculty of medicine , Mansoura University in the period -#102;-#114;-#111;-#109; December 2016 to December 2017. this study was carried out on 120 eyes of 60 patients with astigmatism more than 2 D 82 eyes were normal , 18 eyes were keratoconus , 20 were forme fruste .