PURPOSE: To investigate the relation between blinking and ocular surface conditions and to introduce and examine a new index, the maximum blink interval. METHODS: In a prospective study, the blink rate of subjects under relaxed conditions was determined from a video recording taken by a hidden observer. The maximum blink interval was defined as the longest time subjects can avoid blinking without feeling uncomfortable. RESULTS: Significant changes in the blink rate and maximum blink interval were induced by factors that directly or indirectly affect the ocular surface: topical anesthesia, changing exposed ocular surface area, and wind. Moreover, the blink rate and maximum blink interval were significantly different in dry eye patients compared with healthy volunteers, with the values of the former approaching the values of the latter after use of artificial tears. The maximum blink interval was decreased by the same factors that increased the blink rate, and there was a significant inverse correlation between blink rate and maximum blink interval. Use of video display terminals was associated with decreased maximum blink interval and, hence, the development of dry eye symptoms. CONCLUSIONS: There was an important association among blink rate, maximum blink interval, and ocular surface conditions. The blink rate and our newly introduced measurement, the maximum blink interval, should prove useful in assessing factors that cause dry eye. This prospective study should contribute to the understanding and treatment of dry eyes.
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