A New Perspective on Spontaneous Blinks

Abstract

To investigate whether the central portions of the upper and lower eyelid margins make complete contact during spontaneous blinks. A prospective case series of subjects located in Weinheim, Germany. Data were analyzed from 30 subjects (14 women; mean age, 42.4 ± 12.3 years). A small drop of lissamine green (LG; 0.15 μl) was placed on the keratinized portion of the central lower lid. Spontaneous blinks were recorded by video from a frontal view and simultaneously from a temporal-inferior view (high-speed video). Blinks were analyzed as being complete or incomplete, and the number of blinks necessary to remove the LG was counted. The upper eyelid was observed to grade the extent of misalignment of the lids in the z-axis. This so-called overblinking of the lids was classified using a 5-grade scale (0 = aligned; 1 = less than one-third overblink; 2 = more than one-third to two-thirds overblink; 3 = more than two-thirds to three-thirds overblink; and 4 = more than three-thirds overblink). Correlations were calculated by Pearson correlation (or Spearman rank in nonparametric data), and differences between groups were calculated by unpaired t test (or Mann-Whitney U test in nonparametric data). Contact between lids in spontaneous blinks and lid alignment. Mean blink rate was 14.9 ± 14.1 blinks/minute, and 58.8 ± 22.6% of blinks were incomplete. Blink rate was significantly higher in women than in men (P = 0.007, unpaired t test; female, 22.0 ± 16.8 blinks/minute; male, 8.6 ± 7.2 blinks/minute). Incomplete blinking occurred significantly less often in women (51.2 ± 18.5%) than in men (67.4 ± 24.5%; P = 0.029) but was not related to age (Pearson r = 0.108; P = 0.285). Lissamine green stayed unaltered in spontaneous blinks and, on average, 1.5 ± 0.8 forced blinks were needed to remove the LG. Mean grade of upper lid overblink was 3.0 ± 0.9. Lid overblink was correlated significantly with age (r = 0.456; P = 0.006). Central lid margins do not touch in spontaneous blinks because the lids are not aligned. The author(s) have no proprietary or commercial interest in any materials discussed in this article.