Tear meniscus height, lower punctum lacrimale, and the tear lipid layer in normal aging

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 mm (+/-0.013) in females and 0.010 mm (+/-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.