Changes in contrast sensitivity induced by spherical hydrogel lenses on low astigmats

Contrast sensitivity values were taken on seven astigmatic (cylinder correction under 1.00 diopter) and eight spherical myopes using the Vistech VCTS 6500 System. For the astigmatic group, no significant difference in contrast sensitivity was found between the full subjective correction and an equivalent spherical spectacle prescription, despite the absence of cylinder correction. However, comparing the full subjective correction with an equivalent spherical hydrogel lens, we found a significant decrease in contrast sensitivity while wearing lenses for all but the highest spatial frequency tested. Using a group of spherical myopes, we were unable to demonstrate a decrease in contrast sensitivity as a product of hydrogel lens wear alone. Our findings suggest that there is a measurable decrease in contrast sensitivity as a result of fitting low astigmats with spherical hydrogel lenses which cannot be attributed solely to hydrogel lens wear or the absence of cylinder correction.