The Effects of Mild Ocular Surface Stimulation and Concentration on Spontaneous Blink Parameters

Abstract

Purpose This exploratory, pilot study compared the effects of concentrating on a visual task and a very mild ocular surface air stimulus on multiple blink parameters. Methods Ten subjects participated in this study. There were 2 visits, one with an ocular surface air stimulus (AS) and one without (NS). The AS was set at a level barely perceptible by subjects (approximately 0.6m/sec at the eye). At each visit, subjects performed a high (HC) and low concentration (LC) task. Blinking was tracked and tear-film breakup (TBU) was monitored simultaneously to measure blink parameters, including the interblink interval (IBI), blink amplitude, duration, maximum velocity and TBU before and after each blink. Results During the HC tasks, IBI was significant higher and blink duration was lower (repeated measures ANOVA, p< 0.05) than the LC tasks. The IBI in the AS-LC condition was significantly lower and less variable than in the NS-HC condition, whereas blink duration showed the opposite effect (Hotelling T2 test, p<0.005). There was high individual variation in correlations between blink amplitude and maximum velocity. The area of TBU was not significantly correlated with any blink parameter. Conclusions The lack of correlation between TBU and blinking suggests that many blinks are stimulated by internal controls, rather than direct stimulation of the ocular surface by TBU. This pilot study suggests that even very mild ocular surface stimulation produces opposite effects on the timing and duration of the blink, when compared to concentrating on a visual task. The HC task tends to decrease blink frequency and duration, presumably to minimize interruption by the eyelids, whereas mild ocular surface AS increased blink frequency and duration, most likely to increase protection of the ocular surface.

TFOS DEWS II pain and sensation report

“…Many studies have shown increased spontaneous blinking when the ocular surface is stimulated [315–317]. Recently, Wu et al showed a linear increase in blink rate with increasing air flows applied on the ocular surface [318].…”

Dynamics and function of the tear film in relation to the blink cycle

“…Many blinks are partial (Cruz et al, 2011; Doane, 1980; Harrison et al, 2008; Himebaugh et al, 2009; Wu et al, 2014) and this makes the effects of the turning point more visible than the full blinks in the optical systems we have used. Fig.…”

“…This is just at the sensory threshold (Liu et al, 2009). For a thinning rate of 10 μm/min, this value is increased to about 900 mOsM, while at 20 μm/min, it is increased to very large values, 1830 mOsM at 25 s. It is likely that a subject would blink before reaching such large values, but these values may possibly be reached if the subject is performing a task with intense concentration or is in a controlled experiment and asked not to blink (Cruz et al, 2011; Wu et al, 2014). Results at other times are given in Table 1; such long times are not needed to reach what is currently thought to be high osmolarities in the menisci over the cornea.…”

“…Results at other times are given in Table 1; such long times are not needed to reach what is currently thought to be high osmolarities in the menisci over the cornea. Perhaps these elevated values help signal partial blinking, which occurs frequently (Cruz et al, 2011; Doane, 1980; Wu et al, 2014). …”

“…The images were subsequently hand processed to reveal lid motion and speed as well as other aspects of blinking and tear supply and drainage (Doane, 1981). Progress in optics and computing has led to more automated approaches; we only cite a few of the possible studies (Cruz et al, 2011; Wu et al, 2014). Results from a new stroboscopic imaging system are presented here to illustrate both the blink process and the dynamics of the tear film related to the blink cycle.…”