Eye drift during fixation predicts visual acuity

Abstract

Visual acuity is commonly assumed to be determined by the eye optics and spatial sampling in the retina. Unlike a camera, however, the eyes are never stationary during the acquisition of visual information; a jittery motion known as ocular drift incessantly displaces stimuli over many photoreceptors. Previous studies have shown that acuity is impaired in the absence of retinal image motion caused by eye drift. However, the relation between individual drift characteristics and acuity remains unknown. Here, we show that a) healthy emmetropes exhibit a large variability in their amount of drift and that b) these differences profoundly affect the structure of spatiotemporal signals to the retina. We further show that c) the spectral distribution of the resulting luminance modulations strongly correlates with individual visual acuity and that d) natural intertrial fluctuations in the amount of drift modulate acuity. As a consequence, in healthy emmetropes, acuity can be predicted from the motor behavior elicited by a simple fixation task, without directly measuring it. These results shed new light on how oculomotor behavior contributes to fine spatial vision.

Visual feature tuning properties of short-latency stimulus-driven ocular position drift responses during gaze fixation

“…This is consistent with our earlier observa?ons about ocular posi?on driXs in peripheral Posner-like cueing tasks (Tian et al, 2018). An important implica?on of this is that ocular posi?on driXs are not en?rely random movements, consistent with other evidence (Murphy et al, 1975;Kowler and Steinman, 1979b, a;Ahissar et al, 2016;Tian et al, 2018;Skinner et al, 2019;Bowers et al, 2021;Reiniger et al, 2021;Clark et al, 2022;Nghiem et al, 2022). This evidence again has parallels in the field of microsaccades, which were thought to be random un?l two decades ago (Hafed and Clark, 2002;Engbert and Kliegl, 2003).…”

“…In all, the results of Fig. 5 confirm that ocular posi?on driXs are not always random or stochas?c (Kowler and Steinman, 1979b, a;Ahissar et al, 2016;Tian et al, 2018;Skinner et al, 2019;Bowers et al, 2021;Reiniger et al, 2021;Clark et al, 2022;Nghiem et al, 2022), and that these driXs can reliably reflect localized s?mulus loca?ons in addi?on to exhibi?ng a (poten?ally reflexive) upward driX pulse. Having said that, true dependence of ocular posi?on driXs on localized s?mulus loca?ons should include evidence of spa?ally-directed driX trajectories for the ver?cal dimension as well.…”

Oculomotor routines for perceptual judgments

“…This is not true of all tasks; if fine spatial detail is required for discrimination, gaze has a causal role, and the stimulus must align on the foveola for the task to be performed (Ko, Poletti, & Rucci, 2010). In this case, there is a causal and critical role of gaze; fine eye movements help optimize performance by shifting the eyes so the stimulus falls on the fovea (Clark, Intoy, Rucci, & Poletti, 2022; Intoy & Rucci, 2020). This is a unique feature of vision and suggests eye movements are uniquely adapted to the given task, and are recruited when necessary.…”

Sub-cone visual resolution by active, adaptive sampling in the human foveola

“…Contrarily, recent studies on human psychophysics demonstrated fixational eye motion to be beneficial for fine spatial vision 26,29,30 . Especially drift motion has been increasingly argued to not just be randomly refreshing neural activity, but rather structuring it 26,31,32 and being under central control 33 .…”

“…Drift was shown to improve visual performance in resolution tasks 26,29,35 , and a recent model of early retinal signals suggests that if drift amplitude is tuned to object size, visual acuity would be enhanced 36 . Indeed, considerable differences in ocular drift between individuals exist 32,37 , and subjects exhibiting less drift were shown to have better acuity 32 . If such differences are a consequence of an active, adaptive mechanism, however, and how drift behavior is related to the photoreceptors that sample the retinal image is unknown.…”