Effect of target contrast and luminance on soft contact lens and spectacle visual performance

The visual performance of four soft contact lenses was investigated using visual acuity charts at six contrast levels (from 90 to 8%) under normal (250cd/m2) and reduced 92.5cd/m2) luminances. This investigation reveals significant differences not detected by conventional visual acuity measurements; in general, reducing luminance or contrast increases the magnitude of any recorded difference. Furthermore, the study pointed to a significantly poorer visual performance with spectacles compared to standard thickness soft contact lenses under low luminance and contrast conditions. Finally, a recommended examination routine is described.