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Norihiko Yokoi, MD, PhD; Anthony J. Bron, FRCOphth; John M. Tiffany, PhD; Kunio Maruyama, BS; Aoi Komuro, MD, PhD; Shigeru Kinoshita, MD, PhD

Arch Ophthalmol. 2004;122:1265-1269.

Objective  To investigate the relationship between tear volume and tear meniscus curvature by means of the video meniscometer.

Methods  Eleven eyes of 11 patients with severe dry eye were studied (all female; mean ± SD age, 66.2 ± 7.7 years; 7 left eyes and 4 right eyes), each of whose puncta had been therapeutically occluded. Four instillations of balanced salt solution were given at intervals of 1 minute in each studied eye, with the concentration increasing in 5-µL steps from 5 to 20 µL. Before and after the instillation of balanced salt solution, tear meniscus changes were recorded by video meniscometer and radius of the meniscus was calculated from the printed images by means of the concave mirror formula.

Results  The mean radius of the meniscus increased linearly with increased drop volume (r² = 0.65, P<.001), with mean ± SD radius values of 0.24 ± 0.08 mm at baseline and 0.48 ± 0.13, 0.62 ± 0.13, 0.84 ± 0.26, and 1.00 ± 0.32 mm after separate instillations of 5, 10, 15, and 20 µL of balanced salt solution, respectively. For each subject, a significantly different slope defining the relationship between instilled volume and meniscus radius was seen (0.016-0.063 mm/µL; mean ± SD, 0.039 ± 0.015 mm/µL), which was thought to depend on the difference in capacity of the fluid reservoir over the ocular surface.

Conclusions  This study confirmed that the volume of instilled eyedrops is linearly related to the resulting radius of the tear meniscus, suggesting that this radius is a useful measure in monitoring the tear volume. This is likely to have implications both for dry eye diagnosis and for confirming the efficacy of punctal occlusion in this condition.

From the Department of Ophthalmology, Kyoto Prefectural University of Medicine, Kyoto, Japan (Drs Yokoi, Komuro, and Kinoshita and Mr Maruyama); and Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford, England (Drs Bron and Tiffany). The authors have no relevant financial interest in this article.