Static and dynamic global stereo acuity: effects of age

Abstract

Several investigations have observed that local and global stereo acuity decrease as age increases. However, in these studies the monocular visual acuity of the older population was impaired, and this might explain the observed stereo deficits. In this study we asked, "Does the stereo acuity decrease as age increases for people who have normal monocular visual acuity?" We measured the global static and dynamic stereo thresholds in 58 subjects aged 20–79 years. All subjects were emmetropic and/or had corrected visual acuity of 20/20 or better. None had a history of strabismus, glaucoma, or diabetes mellitus. The stimuli were static or disparity-reversing horizontal gratings-in-depth generated by dynamic anaglyphic random-element stereograms. The visual field was 5.4° × 7.6° and the cyclopean spatial-frequency was 0.63 cycles/deg at a viewing distance of 2 m. The mean luminance through chromatic filters (W ratten 29 and 65) was 3.7 cd/m2. A 0.5 diopter lens was placed in front of chromatic filters to correct for the viewing distance. Disparity was reversed at 1.9 Hz in the dynamic-stimulus condition. A method of adjustments was used to determine the stereo threshold. Five ascending and five descending thresholds were obtained for each subject. The average of 10 thresholds was defined as the subject's stereo threshold. We found that static stereo threshold did not increase with age but that dynamic stereo threshold did significantly increase with age (r = 0.344, df = 56, p < 0.01). We interpret these results as indicating that there is no unique global stereo acuity deficit in the aging population and that the significant decrease in dynamic stereo acuity occurs because of the attenuation of temporal processing in the elderly.