Abstract
Purpose :
The recently discovered Reverse Pulfrich Effect (RPE) shows that depth misperceptions arise when moving objects are viewed with interocular blur differences like those induced by monovision (Burge et al., 2019). The RPE occurs because the image in the blurrier eye is processed more quickly. Monovision is commonly prescribed with contact lenses (CLs), where the difference in optical power between the eyes does not cause an interocular difference in magnification. But the reverse PE was initially demonstrated with trial lenses (TLs), which do introduce magnification differences. The goals of this study are: 1) to demonstrate that the RPE is induced by CLs and 2) to rule out the possibility that interocular differences in magnification can cause the RPE
Methods :
We measured 3 young subjects by changing the onscreen interocular delay of a moving target (white bar 0.25x1.00deg at 5deg/s) on a 3DTV (LG49UH850V) at a viewing distance of 2m. The task was to indicate whether the target was moving right or left when it appeared to be in front of the screen. Nine level psychometric functions were measured using a 2AFC procedure with onscreen delays ranging from -10 to +10ms. The point of subjective equality provided a measure of the neural delay. We performed three primary experiments, selectively perturbing one eye: 1) blur differences (±1.5D) induced by contact lenses, 2) blur differences (+1.5D) induced by trial lenses, 3) interocular magnification difference (±1.04%, no blur)
Results :
We found that both contact and trial lenses induce the RPE: effect sizes were 1.5±0.4ms/D and 1.8±0.6ms/D, respectively. We found no significant delays with interocular magnification differences (-0.3±0.5ms/%). Thus, blur induced by both contact lenses and trial lenses elicits similarly-sized RPEs. For a target moving at 15mph at 5 meters, these effects correspond to depth misperceptions of ~1.5m, near the width of a narrow lane of traffic. In additional experiments, we found i) that dimming one eye causes the darker eye to be processed more slowly in all observers (a Classic Pulfrich effect), and ii) that dimming the blurred eye by an appropriate amount eliminates the Reverse Pulfrich Effect (i.e. an anti-Pulfrich correction)
Conclusions :
As monovision is mainly prescribed with CLs, practitioners should be aware of these corrections can induce depth misperceptions of moving objects
This is a 2020 ARVO Annual Meeting abstract.