Tear turnover rate is reduced in patients with symptomatic dry eye

Tear turnover rate (TTR) is defined as the percent decrease of fluorescein concentration in the tears per minute after the instillation of fluorescein. The purpose of this study was to examine differences in TTR in a sample with symptoms of dry eye and an asymptomatic control sample using the Fluorotron Master Fluorophotometer.

TTR was measured using the OcuMetrics Fluorotron Master. It measures the decay of the fluorescence of high molecular weight fluorescein FITC Dextran instilled into the tear film. Twenty participants (post-menopausal women) were enrolled in the study (10 asymptomatic (age 64.7 +/- 6.99) and 10 symptomatic (age 61.5 +/- 7.98)). Participants were grouped according to either a positive (symptomatic) or negative (asymptomatic) McMonnies Dry Eye Questionnaire, i.e., an indication of self-reported ocular dryness and the use of rewetting/lubricating drops (questions 4 and 5). TTR was measured in the afternoon only. Measurements were made on the right eye with a controlled blink rate (15 blinks/min), for up to 30 min, post-insertion of 2 microl of 2% FITC Dextran (MW 9500). The scan data were used to construct a graph of log fluorescein concentration (ng/ml) as a function of time and the TTR calculated (%/ min = (1- ln (slope)) x 100).

There was a significant difference in the TTR between symptomatic and asymptomatic subjects. Mean TTR (symptomatic) was 4.89 +/-2.74%/min (range, 2.04-11.81) and mean TTR (asymptomatic) was 11.85 +/- 3.31%/min (range, 5.76-16.45) (P < 0.0001).

Fluorophotometry may be used to demonstrate differences in the tear turnover rate in this post-menopausal group of women, with patients experiencing symptoms of dry eye having a lower TTR than the normals.