Optical performance in eyes wearing two multifocal contact lens designs.

The optical performance of eyes wearing soft multifocal contact lenses was studied using the double-pass technique. Retinal image quality was measured in a group of six eyes wearing two different designs of multifocal lenses: an aspheric design and a spheric multicurve design. Measurements were performed for far, intermediate and near vision conditions and with two different pupil diameters: 3 and 5 mm. The results show that the best optical performance is obtained for far vision conditions when no lens is worn. For near vision conditions, the optical performance when the lens is worn is, in general, better than when no lens is worn. When the lens is worn, the optical performance for far and intermediate vision conditions is similar for the aspherical design, but it decreases for near vision conditions. For the spherical multicurve design, the optical performance obtained for far vision conditions is similar to that obtained for intermediate vision conditions for low values of object vergence, but decreases when the object vergence is high and therefore also for near vision. In general, the differences in optical performance are greater for small pupil diameters (3 vs 5 mm). The general trends of the results obtained by computing the modulation transfer function of the contact lens-eye system can also be shown qualitatively by means of double-pass images or quantitatively by computing the Imax/Imed of the image.