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John D. Rodriguez, Keith J. Lane, Endri Angjeli, Stephanie L. Breton, George W. Ousler, III, Mark B. Abelson; Tear Film Dynamics Associated with Squeeze Blink in Dry Eye Subjects. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3725.
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The physical action of the blinking lid is the driving phenomenon governing the maintenance of the tear film. The action of a squeeze blink has been shown to increase the thickness of the tear film. We define a squeeze blink as a direct, conscious blink in which the eyelids exert pressure on each other. The purpose of this exploratory study was to determine whether the additional pressure of the lids caused by a squeeze blink could result in expression of meibomean glands and greater stability of the tear film, which we defined by an increase in break up time as well as an increase in the Ocular Protection Index (OPI 2).
We considered a sample population of 8 dry eye subjects. The dry eye subjects were selected by symptomatology and fluorescein corneal staining > 1 (Ora Scale). While the subject performed a normalized visual task, the subject was asked to perform a squeeze blink and the tear film was examined using fluorescein videography. The subject’s tear film was examined for one minute pre- and post-squeeze blink.
A reduction in tear film breakup time was observed immediately after the squeeze blink. In all cases, the squeeze blink was followed by 3 to 5 full blinks with low IBIs. Mean tear film breakup time decreased from 7.1 seconds in the minute prior to squeeze blink to 1.02 seconds post-squeeze blink (p=.010). This acute response was followed by a return to mean TFBUT of 6.99 seconds (p= 0.040). The same trends occurred in other OPI parameters.
The reduction in tear film breakup time appears to be largely the result of local variations in the tear film distribution. Recovery and improvement of a uniform and stable tear film occurred several blinks after the squeeze blink. This suggests that over expression of the meibomean glands may have adverse immediate effects on tear film stability and no lasting benefits. Furthermore, these results show the need for caution when comparing natural blink to directed blink activity in a diagnostic setting.
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