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Ziwei Wu, Carolyn Begley, Jun Zhang, Linda A. Adebisi, Trefford Simpson; Does Ocular Surface Stimulation Oppose Internal Controls Over Blinking?. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3846.
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Previous studies have shown that blink rate (BR) decreases with concentration and increases with surface irritation (in dry eye and contact lens wear), but little is known about controls over BR and other parameters involved in spontaneous eyeblinks. The purpose of this pilot study was to test the hypothesis that cognitive central nervous system factors (internal) and the ocular surface (external) exert opposing controls over spontaneous blink parameters.
Ten subjects received no ocular surface stimuli (N-OS), artificial tears (T-OS) or a small fan (F-OS) blowing on the eye in 3 separate visits, while engaged in a low concentration (music: LC) and high concentration (video game: HC) task. NaFL was instilled, the tear film monitored and high speed cameras recorded eyelid movements. Custom MATLAB programs analyzed blink parameters, including blink rate (BR), interblink interval (IBI), blink amplitude (BA), blink duration (BD), and maximum velocity (Vm) and data were analyzed using repeated measures ANOVA with Bonferonni post hoc.
The HC task decreased the BR and increased the IBI variability: AVG (±STD) BR for the LC/HC was 19.4±13.5/ 11.6±6.1 for N-OS, 23.3±11.6/ 11.6±5.5 for T-OS, 22.7±6.6/ 18±10.5 for F-OS, while the F-OS increased the BR and decreased the blink variability: STD of IBI (LC) was 1.9±1 for NS and 1.17±0.4 for FS (p=0.027, paired t-test). On average, the BD was decreased with HC and increased with F-OS (LC/HC 0.32±0.07/ 0.28±0.04 for N-OS, 0.31±0.07/0.27±0.06 for T-OS, 0.35±0.09/0.28±0.06 for F-OS), with significant differences between F-OS LC and T-OS HC (p= 0.019, paired t-test). Median BA decreased with HC and increased with F-OS. AVG (±STD) BA% for the music/game was 84±12/ 74±21 for NS, 79±12/ 73±15 for AT, 80±14/ 77±17 for FS. The Vm significantly increased with F-OS HC compared to N-OS LC (p=0.047).
The data from this pilot study support the hypothesis that internal, cognitive controls tend to decrease BR, BA and BD, presumably to minimize interference from the eyelids during concentrating tasks; whereas ocular surface irritation tends to produce the opposite effect, perhaps to increase surface protection during the blink.
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