Comparison of Each Eye According to the Order of Noninvasive Keratographic Tear Film Evaluation

PURPOSE: To investigate the effect of order of examination on the results of noninvasive keratograph tear film evaluation using Keratograph5M in dry eye patients. METHODS: One hundred and four patients with dry eye symptoms were analyzed retrospectively. All patients underwent bilateral noninvasive tear film evaluation using measurements of tear meniscus height (TMH) and noninvasive keratograph break-up time (NIKBUT) obtained using Keratograph5M. Measurements were performed sequentially in the order of right TMH, left TMH, right NIKBUT, and left NIKBUT. RESULTS: There was no statistically significant difference in TMH values between the right and left eyes (0.24 ± 0.08 and 0.23 ± 0.08 mm, respectively). Mean NIKBUT-first (time at first tear film break-up) and mean NIKBUT-average (the mean of all tear film break-up time over the entire cornea) were 6.17 ± 3.28 and 10.00 ± 3.97 seconds, respectively, for right, and 7.43 ± 3.86 and 11.57 ± 4.34 seconds, respectively, for left eyes. In addition, mean NIKBUT-first between right and left eyes, and mean NIKBUT-average between them were statistically significant (p = 0.013 and p = 0.007, respectively). Mean NIKBUT and mean TMH differences were not significantly influenced by right or left eyes, age, or sex (all p > 0.050). Spearman correlation analyses of TMH, NIKBUT-first, and NIKBUT-average results showed moderate positive correlations between right and left eyes (r = 0.470, r = 0.322, and r = 0.576, respectively; p < 0.001). CONCLUSIONS: TMH evaluation was not affected by test order; however, NIKBUT measurement was affected by test order, because of reflex tearing due to forced eye opening during the examination. Therefore, TMH should be evaluated before NIKBUT, and sufficient time interval and caution should be needed between NIKBUT measurements on both eyes.