Baseline blink rates and the effect of visual task difficulty and positionof gaze

Purpose. To compare the baseline blink rates (BBR) measured under different (baseline) conditions, and to compare the brink rates measured when perfor ming two visual tasks of different levels of difficulty at two positions of gaze. Methods. Ln the first single masked experiment, BBR were measured under thr ee different conditions - (i) conversation with the subjects (ii) taking th e visual acuity and (iii) keeping the subjects waiting in an empty examinat ion room. In the second single masked experiment, the subjects were require d to perform an easy task (reading normal English words) and a difficult ta sk (reading mirror-image English words) at primary gaze and down gaze. The orders of the tasks performed were randomly allocated. Results. BBR taken under the three different conditions were significantly different from each other. No significant difference was found between the blink rates measured when performing the two reading tasks if they were per formed at the same position of gaze. The mean blink rates were significantl y lower when performing the tasks at down gaze than when performing the tas ks at primary gaze. No significant differences were found between BBR-waiting and blink rate me asured when the subject was doing the easy task at primary gaze, and betwee n BBR-VA and blink rate measured when the subject was performing the diffic ult task at primary gaze. Conclusions. BBR measured under different (baseline) conditions produced di fferent results so it is important for investigators to describe the baseli ne condition very clearly in studies where BBR are measured. Our results al so indicated that mean blink rate was affected by the position of gaze and not the level of task difficulty.