In vitro power profiles of daily disposable contact lenses

Purpose: To evaluate and compare the distribution of refractive power within the optic zone of different soft contact lenses and to investigate the effect of lens decentration on the power profiles. Methods: The Nimo TR1504 instrument was used to measure the optical power across different aperture diameters (from 1.5 mm to 5.5 mm in steps of 0.5 mm) of four daily disposable contact lenses: DAILIES TOTAL1, Proclear 1-Day, SofLens daily disposable and 1-DAY ACUVUE MOIST. Measurements were performed using a wet cell. Power data were evaluated when contact lenses were in its centered position and after inducing different amounts of lens decentration (from 0.2 mm to 1.0 mm in steps of 0.2 mm). Results: All contact lenses showed an increase - more negative - in lens power with distance from the lens center. The amount of change varied depending on the lens. It was about 10% of lens power for DAILIES TOTAL1 (-0.29 diopters (D)), Softens daily disposable (-0.36 D), and Proclear 1-Day (-0.32 D) whereas 1-DAY ACUVUE MOIST showed a percentage variation of 3.3% (-0.10 D). After inducing a lens decentration up to 1 mm, the power curves were shifted in the negative direction. However, the change obtained in lens power compared with well-centered position was always lower than a quarter of diopter both for all the lenses and aperture diameters. Conclusions: Our results showed a variation of the refractive power from the lens center, becoming more negative toward the periphery, with a negligible effect of the decentration for all disposable contact lenses studied. (C) 2013 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.