THE RELATION BETWEEN INVASIVE AND NONINVASIVE TEAR BREAK-UP TIME

TBUT and NITBUT (tear break-up time and noninvasive tear break-up time , respectively) were measured on four groups of subjects from differen t countries (two groups of Caucasians, two groups of Chinese). No sign ificant difference was found in either TBUT or NITBUT values among the four groups of subjects. Gender of the subjects was not a factor affe cting the TBUT or NITBUT values. The distributions of both NITBUT and TBUT were non-Gaussian and the median value of either parameter was lo wer than those previously reported. The NITBUT values were significant ly higher than the TBUT values in both Caucasian and Chinese subjects. An investigation into the extent of agreement between the TBUT and NI TBUT methods of assessing tear stability indicated that these methods do not agree sufficiently closely (that is, tear stability Values meas ured with the NITBUT technique do not agree with those measured with t he TBUT technique); short average tear break-up values are associated with small differences between the measures, whereas long average tear break-up values are associated with large differences between the mea sures.