Corneal Elevation Changes in Normal Population and Keratoconus Patients Using Different Acquisition Diameters with Scheimpflug Imager

Background:     Keratoconus is a bilateral, progressive, noninflammatory disease of the cornea which often leads to high myopia and astigmatism with an estimated prevalence of approximately 1 in 2000. Objective: To detect the changes in corneal elevation values using different acquisition diameters (8, 9 mm) in both normal population and keratoconus patients. Patients and Methods: This is a cross-sectional clinical trial conducted at the Ophthalmology Department, Menoufia University Hospital, and Tiba eye center, Menoufia, Egypt in the period between January 2019 to December 2020. Two hundred corneas of two hundred subjects were involved and categorized into two groups, a control group with normal cornea100 subjects (group A) and a group with keratoconus100 subjects (group B) both confirmed by clinical examination and pentacam readings. Results: Receiver operating curve (ROC) analysis was conducted to identify the optimal elevation front parameters levels for prediction ofkeratoconus. The best cut-off values for front parameters BFS 8mm, BFS 9mm, BFTE 8mm and BFTE 9mm were 6.5, 10.5,2.5,2.5 with (96%,92%,92%,92% sensitivity, and 96%,96%,80%, 72% specificity), respectively. Also, the best cut-off values for back parameters levels for prediction of keratoconus for BFS 8mm, BFS 9mm, BFTE 8mm and BFTE 9mm were 14.0, 25.5, 6.5 and 9.5 mm with (96%, 96%, 80%, 72% sensitivity, and 88%, 96%, 64%, 88% specificity), respectively. Conclusion: We can conclude that there was a significant increase in elevation back parameters in keratoconus patients compared to control. The best cut-off values for front parameters levels as BFS (8, 9mm) and BFTE (8, 9 mm) was 6.5, 10.5, 2.5, and 2.5 mm, respectively.