Blinking Patterns and Corneal Staining

Abstract

To investigate the blinking patterns of healthy subjects and soft contact lens wearers and determine whether these blinking characteristics were associated with corneal fluorescein staining. Fifteen young soft contact lens wearers and 11 young, healthy subjects participated in the study. The subjects were selected to have no significant eyelid disease. High-speed filming (100 frames per second) was used to capture the natural blinking patterns of the subjects for approximately 3 minutes. Custom written software was used to measure the vertical palpebral aperture at the start and the end of the downward motion of the upper eyelid. The vertical gap between the lids at the lowest point of the upper lid movement during each blink was measured (closed palpebral aperture). Corneal fluorescein staining was quantified on a 0-to-4 scale for each subject. Closed palpebral apertures in the healthy and soft contact lens-wearing subjects showed a wide distribution, with 22% of blinks being incomplete (<2/3 open aperture) in both groups of subjects. In soft contact lens wearers, there was a significant correlation (r = 0.40, P<0.05) between the mean closed palpebral aperture and the grade of corneal staining (primarily located inferiorly). The healthy subjects did not show the same degree of correlation (r = 0.16, P>0.1). However, the distribution of closed palpebral apertures was significantly different between those subjects with corneal staining compared to those without corneal staining (Kolmogorov-Smirnov two-sample test, healthy subjects with P=0.002 and soft lens wearers with P<0.001). The distribution of closed palpebral apertures of healthy and soft contact lens-wearing subjects showed no clear distinction between complete and incomplete blinks. Both groups of subjects show evidence of an association between the mean closed palpebral aperture size (degree of incomplete blinking) and the grade of corneal fluorescein staining, but the association is stronger in soft contact lens wearers.