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Ziwei Wu, Carolyn G Begley, Nicholas Port, Arthur Bradley, Richard J Braun, Peter Ewen King-Smith; The Effects of Ocular Surface Stimulation on Blinking and Tear Secretion. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4430.
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To determine how increasing ocular surface stimulation affects blinking and tear secretion.<br />
Ten healthy subjects concentrated on a visual task, while a pneumatic device generated air flow toward the central cornea. Six flow rates were randomly presented and one microliter 2% fluorescein was instilled before each trial (2mins) to visualize the lower meniscus. Interblink interval (IBI), tear meniscus height (TMH) and fluorescence intensity were measured simultaneously. Tear meniscus fluorescein concentration (TMFC) was calculated from intensity by a mathematical model. In order to normalize individual variation at the beginning of the trail, the maximum difference of TMH and TMFC within each trial were further calculated. Tear secretion response was disengaged from blinking, by calculating tear turnover rate within each IBI (IBI-TTR). The time to the tearing and blink response were quantified for each trial.<br />
Blinking and tear secretion were increased with stimulation. The mean (±SD) IBI was decreased from 9.47±8.79 during the baseline to 1.39±1.11sec during maximum air stimulation. Ocular surface stimulation was significantly correlated with the log IBI, maximum difference of TMFC and TMH (Pearson’s r= -0.47, 0.71 and 0.39, p<0.01, respectively). The IBI-TTR was increased from 0.014±0.013 during the baseline to 0.097±0.045 log(%)/sec during maximum air stimulation and it was significantly correlated with surface stimulation (Pearson’s r= 0.61, p<0.001). Blinking and tearing responses were significantly correlated with each other (Pearson’s r= 0.56, p<0.001). On average, the tear secretion lagged behind the blink response by 6.54±4.07sec.<br />
Both blinking and tear secretion showed a dose-response relationship with increasing ocular surface stimulation, and were highly correlated with each other. The blink response was almost immediate, while tearing lagged by several seconds, possibly due to the time required for tears to arrive in the meniscus. Both of these protective responses originate with ocular surface stimulation, and thus depend on initiation by ocular surface sensory innervation. While this study tested young, healthy subjects to establish normal protective response of the ocular surface, these methods can be used to further understand potential deficiencies in these responses in ocular surface conditions such as dry eye.<br />
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