USING CORNEAL OXYGEN-DEMAND TO OPTIMIZE RIGID CONTACT-LENS DESIGN

To evaluate the effects of base curve radius, overall diameter, and ax ial edge lift on rigid contact lens tear pump efficiency, corneal oxyg en uptake rates were measured on six eyes under three conditions: norm al open eye, after 5 min of static (without blinking) wear, and after 5 min of dynamic (with blinking once every 5 s) wear. The three parame ters were varied one at a time from a standard lens design. Difference s in corneal oxygen demands between the static and dynamic rates provi ded quantitative measures of the tear pump efficiency for each lens de sign. Tear exchange was found to be most sensitively related to change s in base curve radius, followed by overall diameter changes (66.9% as effective) and axial edge lift changes (64.6% as effective). Design e quivalencies (to produce identical tear exchange to a 0.05-mm flatteni ng of base curve toward alignment) were 0.07-mm steepening of the base curve toward alignment, 0.35-mm decrease in overall diameter, or 0.03 7-mm increase in axial edge lift.