Tear meniscus measurement in the diagnosis of dry eye
Assessment of the tear film meniscus is a quantitative, minimally invasive, direct measurement of tear film quantity. The aim of this study was to assess the efficacy of tear meniscus parameter measurement in the diagnosis of dry eye. Tear meniscus radius of curvature, height, width and cross-sectional area (TMC, TMH, TMW, XSA) were determined by photographing an optic section of the inferior tear meniscus (colored with a min volume of fluorescein) at 12 x magnification, and then scanning developed images into a computer analysis program. Fifteen dry eye subjects and 15 age-matched controls were assessed. Dry eye subjects satisfied the criteria of a rose bengal staining score >/= 1, and a mean phenol red thread 15s wetted length </= 10 mm. TMC, TMH and XSA were all reduced in magnitude in the dry eye group compared to the control group (mean +/- SD; TMC: 0.314 +/- 0.160 mm vs. 0.545 +/- 0.259 mm, TMH: 0.244 +/- 0.089 mm vs. 0.461 +/- 00.173 mm, XSA: 0.0082 +/- 0.0048 mm2 vs. 0.0176 +/- 0.0103 mm2, ANOVA, p < 0.05). Both TMC and TMH showed good diagnostic accuracy (166.7% and 160% respectively), with a dry eye referent value of </=0.35 mm for each parameter. TMC and TMH also showed strong correlations with the cotton thread test, non-invasive breakup time, and ocular surface staining scores (p < 0.01). TMH was the most powerful predictor of tear film insufficiency. This study has shown tear meniscus assessment to be a useful alternative to existing tests for dry eye.