Prevalence and Risk Factors for Keratoconus in Young Adults Assessed with Tomography and Corneal Biomechanics: A Prospective Cross-Sectional Study

Purpose: To evaluate the prevalence of keratoconus (KC) and associated risk factors in a previously undiagnosed population at a Brazilian university hospital, using advanced tomographic and biomechanical tools. Design: A prospective, cross-sectional observational study. Methods: A total of 521 participants (1041 eyes) from the staff and students of Gaffrée and Guinle University Hospital, Federal University of the State of Rio de Janeiro, were examined using corneal tomography (Pentacam AXL; Oculus Optikgeräte GmbH) and biomechanical analysis (Corvis ST; Oculus Optikgeräte GmbH). Exclusion criteria included self-reported KC, prior corneal surgery, known corneal pathology, and suspected contact lens warpage. A structured questionnaire assessing demographics, eye-rubbing habits, and family history was administered to all participants before diagnostic examinations. A single experienced examiner performed subjective topometric map evaluations. Objective parameters included the Tomographic and Biomechanical Index version 2 (TBIv2), Corneal Biomechanical Index (CBI), Pentacam Random Forest Index, Belin-Ambrósio Deviation Index, version 3 (BAD-Dv3), and topographic KC classification. Statistical analyses included chi-square tests, odds ratios (ORs), and relative risks (RRs). All prevalence rates are reported per eye. Results: Subjectively, 36.8% of eyes were classified as normal, 31.4% with regular astigmatism, and 5.8% as ectatic or ectasia-suspect (including 4.2% suspected KC, 1.0% KC, and 0.5% pellucid marginal degeneration). Contact lens warpage (15.1%) and other irregular patterns (10.9%) were also noted. Objectively, 5.86% had altered topographic KC classification, 13.16% had pachymetry