Contact lenses can cause the reverse Pulfrich effect and anti-Pulfrich monovision corrections can eliminate it

Abstract

Interocular differences in image blur can cause dramatic misperceptions of the distance and three-dimensional direction of moving objects. This new illusion-the reverse Pulfrich effect-is caused by the optical conditions induced by monovision, a common correction for presbyopia. Fortunately, anti-Pulfrich monovision corrections, in which the blurring lens is slightly darkened, can eliminate the illusion for a wide range of viewing conditions. However, the reverse Pulfrich effect and the efficacy of anti-Pulfrich corrections have previously been demonstrated only with trial lenses. This situation should be addressed, for both clinical and scientific reasons. First, monovision is most commonly prescribed with contact lenses. It is important to replicate these effects in the most common monovision delivery system. Second, trial lenses of different powers, unlike contacts, cause large magnification differences between the eyes. To confidently attribute the reverse Pulfrich effect to differences in optical blur between the eyes, and to ensure that the reported effect sizes are reliable, one must control for magnification. Here, in a within observer study with five separate experiments, we demonstrate i) that contact lenses induce reverse Pulfrich effects that are indistinguishable from those induced by trial lenses, ii) that overall magnification differences do not cause or impact the Pulfrich effect, and iii) that anti-Pulfrich corrections (i.e. darkening the blurring lens) are equally effective when induced by contact lenses and by trial lenses.

Continuous psychophysics shows millisecond-scale visual processing delays are faithfully preserved in movement dynamics

“…To directly compare estimates of processing speed from tracking and traditional psychophysics, we used a standard paradigm to measure interocular delays associated with the Pulfrich effect (Burge et al, 2019; Rodriguez-Lopez, Dorronsoro, & Burge, 2020). The luminance levels in each eye were matched to those used in the monocular tracking experiment.…”

“…It has long been known that interocular differences in luminance cause interocular differences in processing speed; the darker image is processed more slowly (Lit, 1949; Pulfrich, 1922). More recently, it was discovered that interocular differences in blur also cause interocular differences in processing speed: the blurrier image is processed more quickly (Burge et al, 2019; Rodriguez-Lopez et al, 2020). Given that blur decreases contrast and given that decreases in contrast tend to decrease processing speed (Albrecht, 1995; Bair & Movshon, 2004; Levi, Harwerth, & Manny, 1979; Nachmias, 1967; Reynaud & Hess, 2017; Shapley & Victor, 1978; Vassilev et al, 2002), it may at first seem surprising that blur increases rather than decreases processing speed.…”

“…And the severity of the illusion increases in low-light conditions (Rodriguez-Lopez, Chin, Dyer, Burge, in prep). Fortunately, simple but novel combinations of existing ophthalmic interventions hold promise for eliminating these misperceptions (Burge et al, 2019; Rodriguez-Lopez et al, 2020). The continuous target tracking paradigm developed here may prove useful for developing methods for measuring and screening for interocular delays in a clinical setting.…”

“…It has long been known that interocular differences in luminance cause interocular differences in processing speed; the darker image is processed more slowly (Lit, 1949;Pulfrich, 1922). More recently, it was discovered that interocular differences in blur also cause interocular differences in processing speed: the blurrier image is processed more quickly (Burge et al, 2019;Rodriguez-Lopez, Dorronsoro, & Burge, 2020). These phenomena are not simply laboratory curiosities.…”

“…For example, a motorist may misperceive the distance to a cyclist in cross-traffic by the width of an entire lane of traffic (Burge et al, 2019). Fortunately, simple but novel combinations of existing ophthalmic interventions hold promise for eliminating these misperceptions (Burge et al, 2019;Rodriguez-Lopez et al, 2020). The continuous target tracking paradigm developed here may prove useful for developing methods for measuring interocular delays in a clinical setting, where screening a large volume of unpracticed observers would be necessary.…”