BLINK-INDUCED VARIATIONS IN VISUAL PERFORMANCE WITH TORIC SOFT CONTACT-LENSES

Background. Blink-induced lens movement causes a reduction in visual p erformance that is potentially greater with toric than with spherical soft contact lenses because of the combination of vertical lens moveme nt and rotation. This study examined the effect of the two most common methods of toric lens stabilization (prism ballast and dynamic stabil ization) on vision. Method. Four toric soft contact lens wearers were the subjects (astigmatic range 1.25 to 2.25 D). Stimulus presentation (10.5 cpd sine wave grating flashed for 16 ms) occurred at specified t imes up to 400 ms after the blink. Contrast thresholds were determined monocularly with spectacles and the two types of contact lenses. Resu lts. For the grouped data, the prism ballasted lens gave better overal l visual performance than the dynamic stabilization at all times after the blink. Separate analysis of subject data suggested that this gene ral pattern was not true for all individuals. Conclusions. Clinical ev aluation of different lens designs on individual patients is required for achieving the optimum visual performance with toric soft lenses.