Effect of fluorescein on the tear stability of Hong Kong-Chinese.

We used the noninvasive tear break-up time (NITBUT) technique to measure the tear stability of 24 asymptomatic Hong Kong (HK)-Chinese before and after instillation of fluorescein. One eye was used as the test eye while the fellow eye served as control. We compared the NITBUT of the test eyes pre- and postinstillation of fluorescein, and compared the NITBUT of the test eyes measured postinstillation of fluorescein with the NITBUT of the control eyes. After instillation of fluorescein, both longer and shorter NITBUT were recorded in the test eyes; similar results were observed for the control eyes (no fluorescein instilled) between the first and second measurement. The median NITBUT of the test eye pre- and postfluorescein instillation were 13.3 and 13.0 s, respectively. Fluorescein did not cause any significant change in the NITBUT of HK-Chinese and the instillation of fluorescein in one eye does not affect the NITBUT of the fellow eye. Fluorescein did not appear to affect the locations of tear break up (tear defects) observed using the NITBUT test. Tear defects are most frequent near the inferior periphery of the cornea.