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E.B. Papas, A. Dahms, N. Tahhan, N. Carnt; Power Profiles and Short Term Visual Performance of Soft Contact Lenses . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2052.
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To determine the effect on vision of refractive power distribution in the optic zone of soft contact lenses.
Twenty subjects wore each of five contact lens types in one eye only. Lenses were ACUVUE® 2, ACUVUE® ADVANCETM (Vistakon), O2OPTIXTM, NIGHT & DAY® (CibaVision) and PureVisionTM (Bausch & Lomb). Presentation order was randomized and masked. In–eye lens power was adjusted to achieve zero spherical over–refraction prior to carrying out the following visual assessments: High (HCVA) and low contrast visual acuity (LCVA) in normal illumination (1700 Lux), high contrast acuity in reduced illumination (HCLIVA) (17 Lux), subjective visual quality (VQ) using a numerical rating scale and visual satisfaction rating (VS) by Likert scale. Refractive power across the central 5mm was measured at the back surface of all lenses with both Nikon focimeter and Visionix VC 2001.
Group mean responses, for selected variables, are shown in the table below. Comparison between lens types made using analysis of variance with repeated measures and Friedman’s test for Likert scale data showed no significant differences for any of the visual performance variables (p > 0.05). Group mean back vertex power error (BVPE), defined as the difference between labeled power and focimeter measured power, was significantly more negative for ACUVUE® 2 and ACUVUE® ADVANCETM than for other lens types (p < 0.0005). Comparison of power distributions across the optic zone indicated marked differences between the lens types.
Variations in power profile between these lens types did not result in measurable short term visual performance differences. Lenses of equivalent labeled power did not necessarily produce identical refractive effects on–eye. Over–refraction to establish the appropriate back vertex power, for each lens type, is a pre–requisite for optimum vision.
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