Variation of visual acuity with soft contact lenses: a function of luminance

The relationship between visual acuity and luminance with soft contact lenses, compared with the same one obtained with glasses or the naked eye, shows that acuity decreases at the same rate as luminance is reduced. This result differs from what had previously been found in comparing acuity with hard contact lenses and glasses. In the present case, soft lenses conform to the aspherical curvature of the cornea, and therefore the eye wearing soft contact lenses is not affected by spherical aberration, as in the case of hard contact lenses. At the outset, soft lenses produce a somewhat lower visual acuity but with adaptation, acuity improves and becomes equal or better, as evinced by measurements made after three months of wear.