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Edward Ian Pearce, Michael Dorman, Ben C. Wilkinson, Katherine M. Oliver; Effect of Blink Frequency on Tear Turnover Rate. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3726.
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To investigate the effect of blink frequency on tear turnover rate.
Blink frequency was manipulated using a custom computer timer program producing an audible beep. Subjects were instructed to blink at each beep. Compliance was monitored visually. Blink rate was set to the following rates 60, 12 and 6 blinks per minute, corresponding to an inter blink interval (IBI) of 1, 5 and 10 seconds respectively. Tear turnover rate (TTR) was measured at each blink rate over a 20 minute period using an OcuMetrics Fluorotron Master FM2 fluorophotometer. TTR was also measured under natural blink rate when no auditory cue was used. Ten healthy subjects were recruited (mean age 21.5±1.0, range 18-23 years, 7M, 3F). Subjects attended two sessions. Both right and left eyes was used at each session. The order of blink rate conditions was randomized using a Latin square.
It was found that as inter blink interval increased, the tear turnover rate (TTR) decreased. TTR was 21.2 %/min ± 4.7 at 1 sec IBI, 17.6 %/min ± 6.1 at 5 sec IBI, 15.7 %/min ± 3.7 at 10 sec IBI and 19.7 %/min ± 6.5 with a natural blink rate. Statistical analysis showed that there was a difference between the blink conditions. Using post-hoc analysis, a significant difference was found between the TTR at 1sec IBI and that observed at 10 sec IBI (p=0.008) Although a strong indicative trend was observed at the other IBIs, these did not reach statistical significance (p>0.05).
Current accepted knowledge suggests that tear drainage is primarily driven directly via the blink mechanism. It is clear from this study that changes in blink rate do influence tear turnover rate, but only to a minor extent. The study suggests that other factors in the lacrimal functional unit are more important in determining TTR. This is worthy of further study as changes in blink rate in dry eye patients are likely to contribute to, but are not sufficient to explain, their reduced TTR.
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