TEAR BREAK-UP TIME - CLINICAL PROCEDURES AND THEIR EFFECTS

Three successive (representative) values of fluorescein-instillation T BUT (tear break-up time) were obtained from a group of young Hong Kong (HK)-Chinese. The median TBUT1, TBUT2 and TBUT3 were 3.2, 3.8 and 4.5 sec, respectively. Wilcoxon signed-rank tests showed that TBUT1 was s ignificantly different from TBUT2 and TBUT3, but there was no differen ce between TBUT2 and TBUT3. It is therefore important, when measuring the TBUT, to specify which TBUT value was taken as the representative TBUT. Fluorescein was reapplied about six min after the first applicat ion, and the TBUT value re-determined (TBUTR). The median TBUTR was no t significantly different from TBUT1. The subjects were requested to r eturn another day and TBUT values (TBUTW) were determined, with the su bjects opening their eyes as wide as possible, such that the palpebral aperture size was increased. The mean +/- SD normal palpebral apertur e size was 10.0 +/- 1.3 mm, and the mean +/- SD palpebral aperture siz e with the eyes wide open was 11.4 +/- 1.5 mm. The median TBUTW (3.6 s ec) was significantly longer than the median TBUT1 (3.0 sec), but this difference appeared to be due to the extremely long TBUTW of one subj ect; no significant difference was found between the median TBUTW (3.4 sec) and TBUT1 (2.8 sec) when data from this subject were excluded. T here was no significant correlation between changes in palpebral size and TBUT value. (C) 1998 The College of Optometrists. Published by Els evier Science Ltd. All rights reserved.