Video-assessment of tear meniscus height in elderly Caucasians and its relationship to the exposed ocular surface.

Purpose: An adequate volume of tears is considered essential to prevent desiccation of the exposed ocular surface, especially in elderly individuals. Few assessments of tear meniscus height (TMH) have however been reported for elderly individuals.
Methods: Close-up images of the lower marginal tear strip were obtained by videography over about 30 s in 56 elderly individuals (38 women, 18 men; 71 +/- 5 years of age) without significant eye disease and having a functional lacrimal system (Schirmer test). From such an "en face" view, the vertical height of the tear meniscus (TMH) at the lower eyelid was measured from stopped video frames. Firstly, TMH was assessed at the mid-point of the eyelid from five frames separated by 5 s; these values were averaged to give a time-averaged assessment of TMH (a tTMH value). Secondly, a position-averaged method (pTMH) was used in which TMH was assessed at 5 locations along the eyelid margin from a single frame that included several mm of marginal tear strip, and an average value calculated. The videographs were also used to assess palpebral aperture and the exposed ocular surface, a 1 min Schirmer test measure (closed eye) was also made, and keratometry data was available for most subjects.
Results: A wide range of average values was encountered for both tTMH (range 0.057 to 0.271 mm) and pTMH (0.031 mm to 0.325 mm). The group-averaged tTMH value was 0.172 +/- 0.047 mm (median 0.164 mm) while the group-averaged pTMH value was 0.171 +/- 0.058 mm (median 0.168 mm), with no difference being found between the two methods (p = 0.84, paired t-test). With either method, the apparent TMH value was greater when the exposed ocular surface value (average 1.68 +/- 0.51 cm(2)) was lower and vice versa, and was statistically-significant for the tTMH measures (p = 0.02, r = 0.32), but not the pTMH measures (p = 0.18, r = 0.18). Neither TMH measure was related to the Schirmer test values or to central corneal curvature.
Conclusions: The results indicate that healthy elderly individuals can be expected to have a measurable lower marginal tear strip, and that objective assessment of this may be a useful alternative to the Schirmer test. A possible association was found between the measures of TMH and the palpebral aperture height (and thus the exposed ocular surface), and so might need to be considered when TMH is assessed.