Variability of the analysis of the tear meniscus height by optical coherence tomography

Purpose. Tear meniscus height (TMH) is an established parameter indicative of tear film volume and has recently been determined using an optical coherence tomographer (OCT). The purpose of this study was to evaluate the inter and intra observer variability in TMH assessment using OCT. Methods. Ten subjects (6 M, 4 F; aged 32.5 +/- 6.4 years) had 10 consecutive scans taken of their inferior central tear meniscus (5 scans originating at 90 degrees and 5 origination at 270 degrees) using the OCT2 (Humphrey-Zeiss). Images were analyzed by two observers using custom software on three separate occasions. Following a training session among observers, the images were reevaluated to assess differences in variability. Data were analyzed for differences within and across examiners, for the effect of examiner training and between scan directions. Results. The mean TMH and tear volume collapsed across subjects were between 0.24 and 0.25 mm and 25 to 27 nL/mm, respectively. No difference was noted within observers. An interobserver mean volume difference (p = 0.044) was present but was eliminated post training (p = 0.167). Variability was less with scans originating at 90 degrees. Conclusions. The values of the TMH and tear volume are similar to those reported in the literature. Due to the interobserver differences observed, a training session between examiners may prove to be valuable, especially in a large or multicenter study.