Performance characteristics of a hydrophilic concentric bifocal contact lens.

Hydrophilic bifocals designed to achieve simultaneous vision with a central distance zone and annular add zone were evaluated on 15 presbyopic subjects. Simultaneous vision was demonstrated for distance zone diameters from 2.25 to 3.25 mm. Both zones affected over-refraction at distance and near resulting in extra minus required for distance and extra plus required for near. On average, visual acuity was worse than with equivalent spectacle correction. Effects of a night viewing simulation were also studied.