Inter-week variation of meibometry and tear break-up time in healthy subjects.

Clinical relevance: Variation with time in the tear film parameters should be considered by the clinician since the time when measurements are made can influence proper diagnosis.Background: A hallmark of dry eye is an unstable tear film associated with variability in objective daily measures. The purpose of the present study was to evaluate the inter-week repeatability of meibometry, break-up time (BUT) and maximum blink interval (MBI) in healthy subjects.Methods: Forty healthy subjects were recruited for the study. Meibometry, BUT and MBI were performed twice in two sessions, one-week apart. Meibum from the lower eyelid was collected and quantified with the Meibometer MB550. Five meibomian curves were generated by tape and each peak value was averaged as a mean value per session. BUT and MBI were determined three times after fluorescein instillation and recorded by a DV-3 camera attached to the slit lamp. BUT and MBI videos were analysed by a second masked observer. Both BUT and MBI values were calculated by averaging the two most similar measurements of the three evaluated.Results: No statistical difference between inter-week sessions was obtained for the meibometry (p > 0.340; Wilcoxon test), BUT (p > 0.326; Wilcoxon test) and MBI values (p ≥ 0.248; Wilcoxon test). Inter-week differences were low for BUT and MBI when time intervals were no longer than 15 seconds (both p ≥ 0.586; Wilcoxon test). A correlation between BUT and MBI was found (r ≥ 0.668, p < 0.001; Spearman Rho), while a no statistical correlation was obtained between meibometry results and BUT or MBI (all p ≥ 0.194; Spearman Rho).Conclusion: Meibum secretion and the tear film stability present good intersession repeatability, and are stable along with sessions in healthy patients.