Purpose:
To assess tear film stability changes caused by the incomplete blinks.
Methods:
Eleven subjects (mean age 21.3) were enrolled. All subjects had visual acuity of 20/20 or better and normal ocular health. We adopted Visual Display Terminal (VDT) operations of the personal computer in this experiment. Each subject’s blinks were observed by a web camera attached on the top of display. Subjects played a PC game for 60 minutes. Every 15 minutes, the subject’s VDT operations were interrupted for measurement. Ring Break Up Time (RBUT), measured by Auto-Ref Topographer RT-7000 (TOMEY Co., Ltd., Nagoya, Japan) was used as one parameter of tear film stability. The corneal aberrations were measured by OPD-Scan II ARK-10000 (NIDEK Co., Ltd, Aichi, Japan).
Results:
The incomplete blinks and the complete blinks were changing during VDT operations. Both the incomplete and the complete blinks were plotted along symmetrical cubic approximation curves. The RBUT was significantly shortened with 4.33 ± 2.57 seconds as measured after 30 minutes compared with the baseline (8.62 ± 1.54 seconds) measured before VDT operations started (p < 0.01). After 30 minutes elapsed, the ratio of incomplete blinks was decreasing while the ratio of complete blinks was increasing. At the measurement after 45 minutes, the RBUT was extended. The ratio of incomplete blinks began to increase after around 50 minutes. After VDT operations, the RBUT was found to have shortened again.
Conclusions:
An increase of incomplete blink ratio brings about tear film instability.
Keywords: cornea: tears/tear film/dry eye • eyelid • aberrations