Determination of Inferior Tear Meniscus Height and Inferior Tear Meniscus Volume Using Optical Coherence Tomography

Abstract

Abstract: : Purpose:Tear meniscus height (TMH) and tear meniscus volume (TMV) has been shown to be reduced in dry–eyed subjects. A technique that accurately tracks the drainage of fluid from the ocular surface via an assessment of the TMH and/or TMV may play an important role in estimating the retention of rewetting agents on the ocular surface. This study sought to investigate the capability of optical coherence tomography (OCT) to measure the TMH and TMV of the tear film over the course of the day. Methods:The TMH was measured at three locations along the lower lid (centrally and approximately 3 mm from the nasal and temporal canthi) of 20 asymptomatic non contact lens wearers using OCT. No lubricant drops were inserted for 24 hours prior to the study commencement or during the course of the study. Measurements were made in the early morning, mid–day and late afternoon to determine the variation in TMH over the course of the day. Calibrated digital photographs of the lower lid length were taken and this, along with the TMH at the three locations, was used to calculate the volume of the lower tear meniscus. Results:TMH in the nasal and temporal areas was found to be insignificantly different from each other (p>0.05), with a mean (± SD) value of 0.07 ± 0.03 mm and did not vary over the course of the day (p>0.05). TMH in the centre of the lid was significantly greater than that found in the canthal regions (p<0.001) and had a mean (± SD) value of 0.18 ± 0.04. Over the course of the day the central TMH monotonously reduced from 0.18 to 0.16 mm, although this change was not significant (p>0.05). The inferior TMV also reduced over the course of the day, from 3.72 ± 1.62 µL in the morning to 3.06 ± 1.34 µL in the late afternoon (p>0.05). Conclusions:OCT is capable of non–invasively measuring the alteration in TMH and TMV of the lower tear prism and shows much promise in studies in which assessment of these variables is of importance.

Keywords: cornea: tears/tear film/dry eye • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)