Decreases in overall light level increase the severity of the reverse Pulfrich effect

Johannes Burge

Abstract:

The Pulfrich effect is an illusion characterized by the
misperception of the depth and 3D direction of moving
objects. Interocular luminance differences cause the
classic Pulfrich effect; the darker image is processed
more slowly. Interocular blur differences cause the
reverse Pulfrich effect; the blurrier image is processed
more quickly. A common correction for
presbyopia—monovision—intentionally induces the
optical conditions that cause the reverse Pulfrich effect.
The effect sizes, and the fact that tens of millions of
people wear these corrections every day, raise concerns
about public safety. However, although the impact of
overall light level (e.g., nighttime vs. daytime) on the
classic Pulfrich effect has been well characterized, its
impact on the reverse Pulfrich effect is unknown. Here,
using a custom binocular 4f tunable lens optical system
that allows the decoupling of retinal illuminance and
retinal blur, we report how the classic and reverse
Pulfrich effects scale with overall light level. Both effects
increase logarithmically with decreases in light level.
These results motivate a characterization of how light
level interacts with other optical factors (e.g.,
higher-order aberrations) that are likely to impact the
reverse Pulfrich effect and, hence, the perceptual
consequences of monovision corrections.