Purpose
Previous studies considered the possibility that individuals with impaired stereoacuity can be identified by estimating the perceived depth of a target with a suprathreshold retinal image disparity. These studies showed that perceived suprathreshold depth is reduced when the image presented to one eye is blurred, but they did not address, as we did, whether a similar reduction of perceived depth occurs when the stereothreshold is elevated using other manipulations.
Methods
Stereothresholds were measured in 6 adult observers for a pair of bright, 1 deg vertical lines during normal viewing and under 5 conditions that elevated the stereothreshold: (1) monocular dioptric blur, (2) monocular glare, (3) binocular luminance reduction, (4) monocular luminance reduction, and (5) imposed disjunctive image motion. The observers subsequently matched the perceived depth of degraded targets presented with crossed or uncrossed disparities corresponding to 2, 4, and 6 times the elevated stereothreshold for each stimulus condition.
Results
The image manipulations used elevated the stereothreshold by a factor of 3.7 to 5.5 times. For targets with suprathreshold disparities, monocular blur, monocular luminance reduction, and disjunctive image motion resulted in a significant decrease in perceived depth. However, the magnitude of perceived suprathreshold depth was unaffected when monocular glare was introduced or the binocular luminance of the stereotargets was reduced.
Conclusions
Not all conditions that increase the stereothreshold reduce the perceived depth of targets with suprathreshold disparities. Observers who have poor stereopsis therefore may or may not exhibit an associated reduction of perceived suprathreshold depth.