Contrast sensitivities through spectacles and soft contact lenses

Contrast sensitivity function (CSF) measurements were made on nine subjects who wore a spectacle lens on one eye and a soft contact lens on the other eye continuously for 18 hr. The functions were the same for the two types of correction and did not become worse over time. Contrary to an earlier report by Applegate and Massof (1975), there was no evidence of a visual decrement caused by the wearing of soft contact lenses or from the moderately prolonged use of a contact lens. A major difference between our study and theirs was that none of our subjects had more than 0.12 D of astigmatism, whereas their soft contact lens subjects had from 0.75 to 1.00 D of astigmatism. Thus, impairments that were previously noted by soft lens wearers may be limited to astigmatic subjects. In addition, no evidence was found that occasional 18-hr use of soft contact lenses has any measurable, immediate effects on visual acuity as inferred from contrast thresholds.