Assessing tear film stability is an essential part of dry eye disease diagnosis and management. But does the common patient instruction to “blink a few times” beforehand do more harm than good? Researchers from Spain found forced blinks may influence tear film stability. They noted that this finding, published in Optometry and Vision Science, should prompt clinicians to provide clearer blinking instructions while administering dry eye examinations.

The team found that forced blinks significantly shortened tear breakup time (TBUT) in the 33 study participants. The differences in TBUT between natural and forced blinks were 3.2 seconds, 2.4 seconds and 2.1 seconds with the Oculus Keratograph 5M, Medmont E300 and fluorescein testing, respectively. The difference between objective and subjective TBUT was less than one second with both video keratoscopy devices.

The investigators concluded that TBUT is statistically and clinically significantly shorter with unnaturally prolonged blinks than close-to-natural blinks, leading to inaccurate judgments of tear film stability. Likewise, they added that forced blinks seem to induce more abrupt tear film destabilization than close-to-natural blinks.

“It is of paramount importance to give precise instructions about the blink to a subject when conducting tear film stability measurements,” the study authors wrote in their final paper.

Szczesna-Iskander DH, Quintana CL. Subjective and objective evaluation of the effect of blink type on tear-film breakup time and its estimation. Optom Vis Sci. October 28, 2020. [Epub ahead of print].