Diurnal variation in corneo-scleral morphology.

Purpose To characterize diurnal variations in scleral morphological parameters and assess correlations between lifestyle habits and variations in these parameters.Methods This prospective observational study enrolled healthy adult participants. Corneo-scleral morphology was evaluated at five standardized timepoints (9:00, 11:30, 14:00, 16:30, and 19:00) using the Pentacam HR corneo-scleral profile module. Participants completed a lifestyle questionnaire assessing sleep patterns and daily routines. Primary outcome measures included sagittal height (SH) and bulbar slope (BS), with coefficients of variation (CV) across the day calculated for each parameter.Results A total of 109 eyes from 55 participants (mean age: 32.6 ± 12.6 years; 37 female, 18 male) were analyzed. Repeated-measures analysis revealed no statistically significant diurnal variations in scleral parameters (all p-values ≥ 0.069). Secondary analysis identified some significant correlations between CVs of scleral parameters and specific lifestyle habits: washing face in the morning (minimum BS, p=0.007), having breakfast (minimum SH, p≤0.016), drinking coffee in the morning (SH p≤0.040), drinking coffee during the day (mean SH p=0.016), and screen exposure before bedtime (mean SH p=0.036). Statistically significant sex-related differences were observed in minimum BS of the right eye (p=0.020) and astigmatic SH (p=0.042).Conclusions The corneo-scleral profile of healthy eyes remains stable throughout the day, with no significant diurnal changes in SH or BS. Although certain lifestyle habits showed trends toward association with scleral variation, definitive conclusions cannot be drawn.