الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
Chronic allergic eye diseases have become a worldwide ocular problem that affect large portion of population also they can cause many complications that eventually may lead to sever visual impairment. The association between ocular allergy and keratoconus is still not clear. Some investigators confirm the association and others don’t. keratoconus is a corneal pathology that is characterized by a progressive deformation of the corneal curvature, causing visual impairment so it need early detection and management. Keratoconus detection has been significantly optimized in the last years, evolving from simple topographic evaluations of the anterior corneal surface to accurate 3-D structural analyses of the whole cornea. The Pentacam is a cornea and anterior segment tomography device, based on a rotating Scheimpflug camera. Its optical cross-sectional analysis allows imaging of both the anterior and posterior corneal surfaces and, thus, derives a full pachymetric map. It also provides several other data that can be helpful to detect ectasia such as corneal aberrometry and densitometry. This study was conducted to evaluate the effect of chronic allergic eye diseases on corneal topography by using the pentacam scheimpflug imaging system to examine corneal topographic maps for 100 subjects (50 nonallergic and 50 allergic). After obtaining a written informed consent the cases were subjected to full history taking and full ophthalmological examination was conducted in all the cases by using slit lamp biomicroscopy. Corneal topographic parameters (K1, K2 and K max) and corneal maps parameters (back elevation and pachymetric maps) were measured using automatically rotating Scheimpflug camera (Pentacam). The results of this study showed that: •There was no statistically significant difference between studied groups in the demographic data including age and sex. •There were statistically significant differences between the two allergic groups as regards the duration of disease, type of allergy and association with systemic atopy. •There were statistically significant differences between KC group and control group as regards BCVA. •There were statistically significant differences between KC group other two groups as regards RM, Km, Rmin, thinnest location, pachy apex, ART MAX, CTSP, PTI, D and corneal volume. •There were statistically significant differences between allergic groups and control group as regards KMAX and elevation back. •There were no statistically significant differences between the AC without KC group and control group as regards RM, Km, astigmatism power, Rmin, thinnest location, pachy apex, corneal volume and anterior chamber angle. •There were positive correlation between duration of disease and astigmatis power and elevation back. •There were negative correlation between duration of disease and ARTmax, pachy apex and thinnest location. Conclusion : chronic eye allergic diseases are common pathological condition responsible for frequent presentation to the ophthalmology clinic. They cause several changes in the corneal topographic maps that increase with the long duration of the disease and may increase progression of keratoconus. Pentacam is a technique that revealed higher ability to discriminate early changes in corneal topography that help in early detection and management of corneal ectasia. Further studies with a large number of patients in more than one center should be performed.