Contrast sensitivity in the presence of a glare light. Theoretical concepts and preliminary clinical studies.

A method is presented for quantitative measurements of the glare effect of light scattered in the ocular media. The contrast sensitivity function is measured with a television display system. A bright light source is introduced into the field of vision, and the resultant decrease in contrast sensitivity is mea-ured. It is further used to calculate a scattering factor which is a direct measure of the intraocular light scattering. The scattering factor shows a marked increase in patients with early cataracts even if their visual acuity is not affected.