Purpose: We examined the effects of induced retinal illuminance on visual acuity and fusion.
Methods: Fifty adults with best corrected visual acuity of 20/20 or better and normal binocularity and fusion were examined. To examine the effect of retinal illuminance on visual acuity and the effect of binocular difference of retinal
illuminance on fusion, we used neutral dentity filter from 0.1 ND to 4.0 ND. While neutral density filter values were increased, we measured the least size fusion slide by major amblyoscope as well as the best corrected visual acuity.
Results: The best corrected visual acuity and the level of fusion were decreased significantly when monocular retinal illuminance was reduced to 2.0 ND (p<0.01, p<0.01, respectively). Although the visual acuity and fusion were equally
influenced
by retinal illuminance, the effect on fusion was more prominent when retinal illuminance decreased greatly.
Conclusions: These results will be of help for the prevention and early detection of amblyopia, although further study will be needed in order to fully evaluate the influences of other factors on binocular fusion.