Influence of palpebral aperture height on tear pump efficiency

Oxygen uptake rates were measured on 6 human corneas fitted with a standardized rigid contact lens in order to determine the relation between vertical palpebral aperture height and exchange efficiency of tears in such systems. The contribution provided by tear exchange to the oxygen available to the cornea was isolated through the use of lenses of negligible transmissivity (PMMA). Measurements of corneal oxygen uptake were made on the normal open eye, after 5 min of static (with no blinking) open eye contact lens wear, and after 5 min of dynamic (with blinking every 5 s) contact lens wear. The difference between the oxygen demand associated with static conditions (SC's) and that associated with dynamic conditions (DC's) is an index of the tear pump efficiency for each subject. A statistically significant correlation (p less than 0.0001) was found between the vertical palpebral aperture height and the tear bulk-flow of oxygen to the cornea, confirming that small palpebral apertures can restrict lens motion.