Effect of Difference of Binocular Retinal Illuminance on Stereopsis

ABSTRACT

PURPOSE: We examined the effect of induced interocular difference of retinal illuminanace on stereopsis. METHODS: Fifty adults who have normal binocularity were examined with neutral density filters. The mean age was 29.1 years. While the monocular retinal illuminance was gradually reduced by increasing the value of neutral density filters, we measured the best corrected visual acuity and stereoacuity with Titmus test and Lang test. We used neutral density filter from 1.0 neutral density (ND, 10% transmit) to 3.0ND (0.1% transmit) with intervals of 0.2ND. RESULTS: The best corrected visual acuity began to decrease significantly when the value of neutral density filter reached 2.0ND (1% transmit). Stereoacuity also began to decline when the value was 1.4ND(4% transmit) with Titmus test and 1.6ND (2.5% transmit) with Lang test. CONCLUSIONS: Change of retinal illuminance effects more on stereoacuity than visual acuity as stereoacuity decreased earlier by increasing the value of density filters. These results imply that the stereopsis test could be more useful than visual acuity test for detecting ocular abnormalities influencing the retinal illuminance.