The effects of rigid contact lenses overall diameter changes on tear pump efficiency: A comparative study

Abstract

A seriesof three studies was performed to evaluate the effects of rigid contact lens overall diameter changes on tear pump efficiency. In all three studies,corneal oxygen-uptake rates were measured on the right eye of six subjects under three conditions:normal open eye, after 5 minutes of static (without blinking) contact lens wear, and after 5 minutes of dynamic (with blinking once every 5 seconds) contact lens wear. Measurements were
repeatedeighttimesfor eachlens/corneasystem. In StudyI, five lens diameters were used, varying from 8.2 to 9.4 mm in 0.3mm steps, with optic-zone diameters1.4 mm less and all other parameters constant. In Study Il, seven lens diameters were
used, varying from 8.2 to 10.0 mm in 0.3 mm steps, with a constant 7.4 mm optic-zone diameter for all lenses and all other parameters constant. In Study Ill, six lens diameters were used, varying from 7.6 to 10.6 mm in 0.6 mm steps, optic-zone diameters1.4 mm less, base-curve radii varying with optic-zone
diameter to maintain a constant apical tear-layer thickness,and all other parameters constant. A reduction in corneal oxygen demand with decreasing lens overall diameter was seen under dynamic conditions in all three studies.Greatest and most consistent tear pump efficiencies, as reflected by large differences between static and dynamic measurements, were also found with the smallest lenses in all three studies.