Prevalence of keratoconus in first-degree relatives: a corneal tomography–based screening study

Keratoconus (KC) is often underdiagnosed in its early stages, leading to missed opportunities for timely intervention, especially among subclinical cases in first-degree relatives of patients with KC (FDRKC). This study aimed to evaluate whether screening FDRKC can effectively expand the reach of care and mitigate the risk of vision loss. Specifically, we estimated the prevalence of KC and KC traits among FDR KC compared to the FDR of tomographically normal individuals (FDRcontrol). This cross-sectional study included 195 FDR of 89 KC patients and 199 FDR of 100 controls. Using tomographic analysis, cases were classified as normal, KC, or KC trait, based on the McDonnell-Rabinowitz criteria. Prevalence ratios, odds ratios, and Mann-Whitney U tests were used to compare parameters between groups. Statistical significance was set at p < 0.05, and the effect sizes were computed (r = Z/√N). All analyses were conducted using STATA 17.0. The prevalence of KC and KC traits was significantly higher in FDRKC (12.3% and 35.4% respectively) compared to FDR-controls (1% and 3% respectively). Pachymetry revealed a median difference of 50 μm between FDRKC and FDR-control, with an effect size > 0.5, indicating strong statistical significance and may be clinically relevant. This is the first Indian study to exclusively screen for KC among family members using tomography, emphasizing the importance of targeted screening in populations with an increasing KC prevalence. Our findings advocate integrating family screening into routine care to identify subclinical cases early and to prevent vision loss in regions showing increasing trend in KC prevalence.