الفهرس 
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Abstract
Keratoconus is a corneal pathology that is characterized by a progressive deformation of the corneal curvature, affecting the visual health of patients. 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. Among the numerous morphologic parameters that can be measured by modern examination techniques is the corneal volume. It reflects topographical and pachymetric changes and characterizes corneal morphometric changes with a single value. This study was conducted to investigate the validity of corneal volume as penatacm parameter in differentiation of keratoconus from normal corneas. This cross section comparative case control study included 120 eyes; 60 eyes of 37 keratoconic patients and 60 eyes of 32 normal subjects recruited from Mansoura ophthalmic center, Mansoura University, Egypt, within the period between July 2019 to June 2020. After obtaining a written informed consent, in the preoperative period, 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 (Frontal and back elevation and pachymetric maps) were measured using automatically rotating Scheimpflug camera (Pentacam). The corneal volume was calculated in a 3mm, 5mm and 7mm diameter zone around the corneal apex. The results of this study showed that: • There was no statistically significant difference between the two groups in the demographic data including age and sex. • There was statistically significant increase in the different topographic parameters including the mean K1, K2 and K max in the studied keratoconic eyes in comparison to the control group. • The UCVA and BCVA (expressed in log mar) in the keratoconic eyes were significantly higher as compared with the normal eyes. • The mean ART max of the eyes in the keratoconus was lower as compared with the normal group. • The mean front elevation and back elevation of the eyes in the keratoconus group were statistically significantly higher as compared with the normal group. • The mean corneal volume at the total area, 3mm, 5 mm and 7 mm zones of the eyes in the keratoconus group were statistically significantly lower as compared with the normal group. • There is a statistically significant negative correlation between total corneal volume with k1, k2, k- Max, Front elevation and Back elevation. There is a statistically significant positive correlation between cornel volume with Thinnest location and ART max. • At the 3 mm and 5mm zone, there is a statistically significant negative correlation between cornel volume with UCVA, BCVA, k1, k2, k- Max, Front elevation and Back elevation. Also, there is a statistically significant positive correlation between cornel volume with Thinnest location and ART max. • At 7 mm zone, there is a statistically significant negative correlation between cornel volume with k1, k2, k- Max, Front elevation and Back elevation. Also, there is a statistically significant positive correlation between cornel volume with Thinnest location and ART max. With increasing the area of the corneal volume, the diagnostic accuracy of differentiating keratoconus from normal eyes decreases. The highest AUC was found with 3 mm³ zone (0.868) and the lowest AUC was found with total area (0.724).