Objective optical assessment of tear-film quality dynamics in patients with meibomian gland dysfunction and aqueous-deficient dry eye optical quality changes in different dry eye subtypes

PURPOSE: To evaluate the optical quality and tear-film dynamics in patients with aqueous-deficient or evaporative subtype of dry eye disease (DED). METHODS: Twenty-five aqueous-deficient dry eye (ADDE) patients, 25 DED patients with meibomian gland dysfunction (MGD), and 25 healthy subjects were included in this study. Vision-related health-targeted quality of life was evaluated using the Ocular Surface Disease Index (OSDI) questionnaire. Dynamic recording with a double-pass system (Optical Quality Analysis System [OQAS]) was performed in right eyes. Scattered light was measured as the objective scatter index (OSI) at 0.5-second intervals over 20 seconds without blinking. Then, we recorded OSI every 0.5 seconds within a 20-second period with the subjects asked to blink freely. Several parameters were established to evaluate the dynamic alterations of optical quality and the effects of blinks: OSI, OSI standard deviation (SD), ΔOSI, ΔOSI/time, blinking change (BC), and blinking frequency (BF). Additional clinical examination included tear film break-up time (BUT), Schirmer I test (SIT), fluorescein staining grade (FL), meibomian gland quality, meibomian gland expressibility, and meibomian gland drop-out. RESULTS: The OSI, SD, ΔOSI, ΔOSI/time, BC, and BF were significantly higher in DED patients than controls (P < 0.01, respectively). The OSI, SD, ΔOSI, ΔOSI/time, BC, and BF were significantly higher in patients with MGD than patients with ADDE (P < 0.01). In the MGD group, BUT, FL staining score, lid abnormality, meibomian gland expressibility, and meibomian gland drop-out were correlated with Δ OSI and Δ OSI/time. CONCLUSION: Dry eye patients with MGD had significant alterations of optical quality compared with ADDE patients. The double-pass system has potential to be a useful quantitative method to evaluate the optical quality and tear-film dynamics in patients with dry eye.