Age-related changes in binocular vision: detection of noise-masked targets in young and old observers

This study investigated the effects of age on binocular unmasking. This term denotes the fact that a visual signal embedded in noise is detected appreciably better when the stimulus complex contains interocular cues (dichoptic condition) than when such cues are absent (binoptic condition). Detection thresholds for two Gabor signals differing in spatial frequency were determined in young and old adults with no identifiable ocular pathologies. The signals were embedded, in both conditions, in two-dimensional Gaussian noise. Binocular Masking Level Differences, defined as the difference between the binoptic thresholds and the dichoptic thresholds, did not change with age; however, the older adults showed higher binoptic thresholds with both signals and higher dichoptic thresholds with only the lower-spatial-frequency signal. For both groups, binoptic and dichoptic thresholds increased with spatial frequency. The implications of these results are discussed.