Study: Diurnal tear meniscus variations

I put a technical title on the post as a signal that probably only the technically inclined will care.... It should go without saying, though, that the more we (speaking collectively) know about the features/behavior of a normal, healthy tear film, the better we can understand our tear film when it's diseased.

Diurnal Variation of Upper and Lower Tear Menisci.
Shen M, Wang J, Tao A, Chen Q, Lin S, Qu J, Lu F
School of Ophthalmology and Optometry, Wenzhou Medical College, Wenzhou, Zhejiang, China.

PURPOSE: To determine diurnal variation of tear menisci around upper and lower eyelids in normal subjects. DESIGN: Prospective laboratory investigation. METHODS: Twenty young healthy Chinese subjects (10 women and 10 men; mean age, 21.3 years; range, 20 to 26 years) with no history of contact lens wear or previously diagnosed dry eye were recruited. A custom-built, real-time anterior segment optical coherence tomography (OCT) instrument was used simultaneously to image the upper and lower tear menisci. Repeated measurements immediately after blinking were conducted on both eyes during a 24-hour period, including immediately before and after sleeping. Dimensional information of the tear menisci were obtained from the OCT images using custom software. RESULTS: There were no significant differences between right and left menisci, nor were there any differences between females and males in the lower tear meniscus (P > .05, repeated-measurement analysis of variance [ANOVA]). Although the lower tear meniscus variables were correlated strongly with upper meniscus variables, the lower meniscus was significantly greater than the upper one. Significant diurnal variations (P < .05, repeated-measurement ANOVA) of all measured variables were observed during the study period. Tear menisci were significantly increased at eye opening after overnight sleep compared with the baseline before sleep at 10 PM (P < .001, post hoc tests). They remained elevated up to 10 minutes after eye opening (P < .001, post hoc tests). CONCLUSIONS: Real-time OCT can provide useful information regarding the dynamics of the tear system. Diurnal variation of the upper and lower tear menisci occur.