Abstract
Purpose: :
This pilot study examines blinking parameters in the presence of a mild ocular surface stimulus while varying task concentration to explore the relationship between cognitive and ocular surface controls over blinking.
Methods: :
10 subjects played a game (HC: high concentration) or listened to music (LC: low concentration) for 2 min with either no stimulus (NS) or a mild ocular surface stimulus (SS) created by fan that was set to a very light breeze barely felt by subjects (0.6m/s). FL was instilled and the tear film and eyelid movement were videotaped. Custom MATLAB programs analyzed blink parameters, including the interblink interval (IBI), blink amplitude (BA), blink duration (BD), and maximum lid velocity (Vmax).
Results: :
The IBI increased with HC tasks and decreased with the SS; the AVG ±STD (sec) for LC/HC was 4.63± 3.39/ 6.43± 3.28 for NS and 2.85± 0.78/ 4.59± 3.23 for SS. The variation of IBI between subjects was significantly decreased from the NS HC to the SS LC task (p= 0.026, paired t-test). BA and BD showed no significant differences among conditions, but, on average, HC decreased the BA and BD, whereas SS increased the BD. BA% AVG ±STD for LC/HC was 86± 16.6/ 75± 23.1 for NS, 80± 17.5/ 80± 20.0 for SS; BD AVG ±STD (msec) for LC/HC was 259.7± 49.9/ 241.3±33.4 for NS, 286.0± 79.2/ 225.9± 44.1 for SS. BA and Vmax were significantly correlated (r= 0.728, p=0.01), whereas BA and BD were not (Spearman r= 0.181, p=0.65), except during the SS HC task (r=0.585, p<0.001). Down and up phase Vmax and BD were significantly correlated (r= 0.768 and 0.634 for Vmax and BD respectively, p<0.01). IBI was not correlated with any other blink parameter.
Conclusions: :
The ocular surface stimulus used in this study, which was set to simulate very light air flow at the eye, was associated with a decreased and less variable IBI (or increase in blink rate). The BA and BD changed less with task; thus, the IBI was the most sensitive blink parameter in response to this mild stimulus. However, it was not correlated with other blink parameters, suggesting that the initiation of a blink may be controlled separately from its fullness, speed and duration.
Keywords: cornea: tears/tear film/dry eye • eyelid • cornea: clinical science