Effect of illumination on scores with instrument acuity tests.

To evaluate the effect of variation in illumination on Ortho-Rater scores, acuity measurements were collected from 55 college students. Illumination was varied from 10 to 125% of standard. Near and far acuity scores, for both eyes and for the right eye, were tabulated. Decreases in illumination as great as one-fourth of standard, or increases as great as one-fourth of standard, did not affect visual acuity scores. Near acuity suffers to a greater degree than far acuity scores when illumination is decreased more than 25%. (PsycINFO Database Record (c) 2010 APA, all rights reserved)