INFLUENCE OF SOFT CONTACT-LENS DESIGN ON CLINICAL-PERFORMANCE

A double-masked, randomized study in four parts was conducted to evalu ate the effect of varying certain soft contact lens design parameters on clinical performance. The effects of varying back optic zone radius (BOZR) (8.20 to 9.00 mm), back surface design (monocurve, bicurve, as pheric), edge thickness (0.12 to 0.24 mm), and back vertex power (+1.0 0 to -6.00 D) were investigated using test lenses manufactured in a hi gh water content material. In each part of the study, between 20 and 3 5 volunteer subjects wore a range of lenses which were assessed after >30 min settling periods. Postblink movement and lens ''tightness'' as assessed by the push-up test were unaffected by the variation in BOZR . Lenses of flatter BOZR centered lower and more temporally than steep er lenses. Lenses of similar back surface sagittal depth, but differin g in terms of back surface design, did not center the same; the monocu rve lenses decentered more than bicurve or aspheric lenses. Edge thick ness had no significant effect on comfort or lens fit. Plus power lens es resulted in more postblink movement than minus lenses of similar po wer. The results are discussed in relation to the design and fitting o f soft contact lenses.