The purposes of this study are to investigate the tear meniscus height (TMH), lipid layer, and critical dimensions of the lower punctum lacrimale (DPL) in normal human subjects over a large age range; and to determine the shape and general characteristics of the lower punctum lacrimale in a normal population.
TMH and DPL were measured using a graticule set at the eyepiece of a slit lamp biomicroscope (magnification 32x). Lipid layer was assessed by interferometry (Tearscope, Keeler). Only one eye (right) of each subject was assessed. All subjects were normals without any tear-related disorders and/or symptoms.
Four hundred forty-four subjects were assessed (268 females, age range, 6–91 years; 176 males, age range, 6–91 years). Mean (± standard deviation) TMH in females was 0.19 mm (± 0.11) and in males was 0.19 mm (± 0.10). TMH was related to age (x): in females, TMH = 0.13 + 0.0009x (r = 0.2393, p < 0.001); in males, TMH = 0.14 + 0.0008x (r = 0.2492, p < 0.001). TMH increased from 0.15 mm (± 0.06) in the young (<20 years) to 0.21 mm (± 0.10) in the elderly (>80 years). The punctum was closed in 10.8%, slit shaped in 24.3%, oval in 5.4%, and round in 59.5% of all cases. Mean age and TMH of those presenting with closed puncta was significantly higher than those presenting with open puncta (p < 0.001). Mean (± standard deviation) area of open puncta was 0.008 mm2 (± 0.013) in females and 0.010 mm2 (± 0.018) in males. The difference was not significant. Diameter of round puncta was inversely related to age in females (r = -0.4985, n = 149, p < 0.001) but not within the males. A total of 14.6% of females and 12.5% of males presented with no discernible lipid layer. Lipid layer tended to be thinner in older subjects (one-way analysis of variance, F = 6.667, p < 0.001). There was no clear relationship between TMH and the lipid layer.
There is a gradual increase in TMH and shift in size and shape of the punctum lacrimale with advancing years. Age-related changes in the lipid layer are expected to reduce tear volume by way of increased evaporation. On balance, it would appear any effects on tear volume by a thinning lipid layer are outweighed by changes in the puncta.