Effects of target distance and pupil size on letter contrast sensitivity with simultaneous vision bifocal contact lenses.

摘要: Using simulated presbyopia we measured the effects of target vergence and pupil size on letter contrast sensitivity while subjects wore accurately centered simultaneous vision bifocal contact lenses. These experiments examined increase in depth focus provided by two lenses, near distance vision. Monocular was assessed with three different designs soft First, as a single control, Bausch & Lomb, Optima 38 lens corrected for distance. We then an Allergan Optical, Hydron Echelon, which is diffractive CIBA Vision, Spectrum, concentric design, center-near, two-zone bifocal. In general both lenses improved at but decreased (when compared to lens). With fixed 3.5-mm artificial pupil, Echelon had clear peaks sensitivity, one (0.00 D) (-2.00 D), Spectrum no peaks. Performance depended its center zone size. Near sizes that ranged from 1 6 mm. The results showed visual performance almost independent diameter up 3 4 mm but, predicted, critically