To investigate the relationship between tear volume and tear meniscuscurvature by means of the video meniscometer.
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 instillationsof balanced salt solution were given at intervals of 1 minute in each studiedeye, with the concentration increasing in 5-µL steps from 5 to 20 µL.Before and after the instillation of balanced salt solution, tear meniscuschanges were recorded by video meniscometer and radius of the meniscus wascalculated from the printed images by means of the concave mirror formula.
The mean radius of the meniscus increased linearly with increased dropvolume (r2 = 0.65, P<.001), with mean ± SD radius values of 0.24 ± 0.08mm 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 20µL of balanced salt solution, respectively. For each subject, a significantlydifferent slope defining the relationship between instilled volume and meniscusradius 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 capacityof the fluid reservoir over the ocular surface.
This study confirmed that the volume of instilled eyedrops is linearlyrelated to the resulting radius of the tear meniscus, suggesting that thisradius is a useful measure in monitoring the tear volume. This is likely tohave implications both for dry eye diagnosis and for confirming the efficacyof punctal occlusion in this condition.