Effect of distance vision and refractive error on the spontaneous eye blink activity in human subjects in primary eye gaze

PURPOSE: To evaluate whether visual target character and visibility affects spontaneous eye blink rate (SEBR) in primary eye gaze and silence. METHODS: Video recordings were made of young healthy adults who were either emmetropic (n = 32) or who wore spectacles for refractive error (range −4.75 D and +4.50 D (n = 31). Emmetropes had 5 min recordings made whilst seated and looking towards a distant whiteboard. For spectacle wearers, recordings were made whilst looking towards the whiteboard with a 35 mm sized cross, and repeated after spectacle removal. The average number of eye blinks over 5 min was assessed, and its intra-subject variability as the coefficient of variation (COV). RESULTS: Over 5 min without a distance target, an average SEBR of 10.4 blinks/min was observed in emmetropes with a of COV = 38.1%, and a significant increase in SEBR over the 5th minute to 13.6 blinks/min. Hyperopes being asked to look towards a distant target showed the essentially same blinking rate of 11.1/min with or without spectacle wear with the intra-subject variability (COV) being 21.3%. Myopic subjects showed a slightly higher SEBR if looking towards a target without their spectacles (12.4 vs. 11.0 blinks/min), with the COV being 18.8%. CONCLUSIONS: The studies indicate that some form of visual target could be useful to promote constancy of spontaneous eye blink activity over time, but that a distance visual target (when provided) does not need to be seen clearly.