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Title
Abstract
Summary
Results and Discussion
Psychophysical Results
Experimental Model and Subject Details
Procedure
Generalizing Results to the Real World
Quantification and Statistical Analysis
References

Monovision and the Mispe rception of Motion Graphical

Profile image of Johannes BurgeJohannes Burge

2019

https://doi.org/10.1016/J.CUB.2019.06.070
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18 pages

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Abstract

Highlights d Monovision induces interocular blur differences and a mismatch in processing speed d The speed mismatch means a common lens correction can cause dramatic motion illusions d Drivers may misperceive the distance of cyclists by the width of a narrow street lane d Novel combinations of non-invasive ophthalmic interventions can abolish the illusion

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Impacts of Induced Monocular Blur on Visual Functions
NURA UMAR IBRAHIM

2019

Anisometropia relates to the differences in refractive power between both eyes. Hence, anisometropia is expected to have deleterious effects on visual functions due to dissimilar retinal images formed on both eyes. This study explored the outcome of induced blur in terms of a refractive defocus on visual functions. Imposing different levels of blur was believed to mimic the anisometropia condition. Twenty emmetropic adults enrolled in this study. Myopia, hyperopia and astigmatism were induced using soft contact lenses in steps of 1.0 Dioptre (D) ranging from 1.00DS until 4.00DS as well soft toric contact lenses 1.00DC until 4.00DC (with the rule (WTR). Visual acuity (Standard logMAR), contrast sensitivity (Pelli Robson), stereoacuity (TNO stereotest) and aniseikonia (retinal image sizes) (Smart Optometry application) were assessed at baseline and each level of defocus. Results: All myopic, hyperopic and astigmatic anisometropia resulted in significant deterioration of visual acuity,...

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Small-aperture monovision and the pulfrich experience: absence of neural adaptation effects
Dionysia Petratou

PLoS ONE, 2013

Purpose: To explore whether adaptation reduces the interocular visual latency differences and the induced Pulfrich effect caused by the anisocoria implicit in small-aperture monovision. Methods: Anisocoric vision was simulated in two adults by wearing in the non-dominant eye for 7 successive days, while awake, an opaque soft contact lens (CL) with a small, central, circular aperture. This was repeated with aperture diameters of 1.5 and 2.5 mm. Each day, monocular and binocular pattern-reversal Visual Evoked Potentials (VEP) were recorded. Additionally, the Pulfrich effect was measured: the task of the subject was to state whether a a 2-deg spot appeared in front or behind the plane of a central cross when moved left-to-right or right-to-left on a display screen. The retinal illuminance of the dominant eye was varied using neutral density (ND) filters to establish the ND value which eliminated the Pulfrich effect for each lens. All experiments were performed at luminance levels of 5 and 30 cd/m 2. Results: Interocular differences in monocular VEP latency (at 30 cd/m 2) rose to about 12-15 ms and 20-25 ms when the CL aperture was 2.5 and 1.5 mm, respectively. The effect was more pronounced at 5 cd/m 2 (i.e. with larger natural pupils). A strong Pulfrich effect was observed under all conditions, with the effect being less striking for the 2.5 mm aperture. No neural adaptation appeared to occur: neither the interocular differences in VEP latency nor the ND value required to null the Pulfrich effect reduced over each 7-day period of anisocoric vision. Conclusions: Small-aperture monovision produced marked interocular differences in visual latency and a Pulfrich experience. These were not reduced by adaptation, perhaps because the natural pupil diameter of the dominant eye was continually changing throughout the day due to varying illumination and other factors, making adaptation difficult.

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Oculomotor contribution to the change in perceived speed with viewing distance
Robert Patterson

Journal of the Optical Society of America A, 2008

An array of moving circular stimuli was used to determine whether perceived speed is affected by the oculomotor responses associated with changes in viewing distance. The perceived speed of stimuli viewed at either 0.33 or 1.33 m was compared to the perceived speed of a similar stimulus viewed at a distance of 5.5 m. In addition, a control condition was run in which changes in perceived speed were compared for monocular viewing of the 0.33 m and 5.5 m stimuli. In the binocular condition, there were statistically significant decreases in perceived speed of about 11% for the 0.33 m viewing distance, and about 6.5% for the 1.33 m viewing distance. There was no significant decrease in perceived speed in the monocular condition. This latter finding, along with the similar appearance of the near and far stimuli in the monocular condition, suggests that ocular vergence (as opposed to accommodation or vergence-accommodation) was the primary determinant of the change in perceived speed with changes in binocular viewing distance. Although the change in perceived speed with fixation distance was relatively small, the data from all observers were in the direction of speed constancy. Thus, to the extent that vergence is a cue to egocentric distance, the present data suggest that egocentric distance is used to scale the perceived speed of targets moving at different distances from the observer.

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Manfred Fahle

Naturwissenschaften, 2001

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2008

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Reduced surround suppression in monocular motion perception
Jenny Read

Journal of Vision

Motion discrimination of large stimuli is impaired at high contrast and short durations. This psychophysical result has been linked with the center-surround suppression found in neurons of area MT. Recent physiology results have shown that most frontoparallel MT cells respond more strongly to binocular than to monocular stimulation. Here we measured the surround suppression strength under binocular and monocular viewing. Thirty-nine participants took part in two experiments: (a) where the nonstimulated eye viewed a blank field of the same luminance (n = 8) and (b) where it was occluded with a patch (n = 31). In both experiments, we measured duration thresholds for small (1 deg diameter) and large (7 deg) drifting gratings of 1 cpd with 85% contrast. For each subject, a Motion Suppression Index (MSI) was computed by subtracting the duration thresholds in logarithmic units of the large minus the small stimulus. Results were similar in both experiments. Combining the MSI of both experiments, we found that the strength of suppression for binocular condition (MSI binocular = 0.249 ± 0.126 log 10 (ms)) is 1.79 times higher than under monocular viewing (MSI monocular = 0.139 ± 0.137 log 10 (ms)). This increase is too high to be explained by the higher perceived contrast of binocular stimuli and offers a new way of testing whether MT neurons account for surround suppression. Potentially, differences in surround suppression reported in clinical populations may reflect altered binocular processing.

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Visual Perception: Monovision Can Bias the Apparent Depth of Moving Objects
Jenny Read

Current Biology

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Interocular differences in visual latency induced by reduced-aperture monovision
Dionysia Petratou

Ophthalmic and Physiological Optics, 2012

Purpose: To explore the interocular differences in the temporal responses of the eyes induced by the monocular use of small-aperture optics designed to aid presbyopes by increasing their depth-of-focus. Methods: Monocular and binocular pattern-reversal visual evoked potentials (VEPs) were measured at a mean photopic field luminance of 30 cd/m 2 in seven normal subjects with either natural pupils or when the non-dominant eye wore a small-aperture contact lens (aperture diameter 1.5, 2.5 or 3.5 mm, or an annular opaque stop of inner and outer diameters 1.5 and 4.0 mm respectively). Responses were also measured with varying stimulus luminance (5, 13.9, 27.2 and 45 cd/m 2) and a fixed 3.0 mm artificial pupil. Results: Mean natural pupil diameters were 4.7 and 4.4 mm under monocular and binocular conditions respectively. The small-aperture contact lenses reduced the amplitude of the P100 component of the VEP and increased its latency. Interocular differences in latency rose to about 20-25 ms when the pupil diameter of the non-dominant eye was reduced to 1.5 mm. The measurements with fixed pupil and varying luminance suggested that the observed effects were explicable in terms of the changes in retinal illuminance produced by the restrictions in pupil area. Conclusions: The anisocoria induced by small-aperture approaches to aid presbyopes produces marked interocular differences in visual latency. The literature of the Pulfrich effect suggests that such differences can lead to distortions in the perception of relative movement and, in some cases, to possible hazard.

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Contact lenses, the reverse Pulfrich effect, and anti-Pulfrich monovision corrections
Johannes Burge

Scientific Reports, 2020

Interocular differences in image blur can cause processing speed differences that lead to dramatic misperceptions of the distance and three-dimensional direction of moving objects. This recently discovered illusion-the reverse Pulfrich effect-is caused by optical conditions induced by monovision, a common correction for presbyopia. Fortunately, anti-Pulfrich monovision corrections, which darken the blurring lens, can eliminate the illusion for many viewing conditions. However, the reverse Pulfrich effect and the efficacy of anti-Pulfrich corrections have been demonstrated only with trial lenses. This situation should be addressed, for clinical and scientific reasons. First, it is important to replicate these effects with contact lenses, the most common method for delivering monovision. Second, trial lenses of different powers, unlike contacts, can cause large magnification differences between the eyes. To confidently attribute the reverse Pulfrich effect to interocular optical blur differences, and to ensure that previously reported effect sizes are reliable, one must control for magnification. Here, in a within-observer study with five separate experiments, we demonstrate that (1) contact lenses and trial lenses induce indistinguishable reverse Pulfrich effects, (2) anti-Pulfrich corrections are equally effective when induced by contact and trial lenses, and (3) magnification differences do not cause or impact the Pulfrich effect. Monovision is a widely prescribed correction for presbyopia, the age-related loss of focusing ability, impacting 2 billion people worldwide 1,2 . Monovision corrections serve as an alternative to reading glasses, bifocals, and progressive lenses for millions of people . With monovision, each eye is fit with a lens that sharply focuses light from a different distance. One eye is corrected for 'far vision' , while the other eye is corrected for 'near vision' . Monovision thus intentionally induces differences in image blur between the eyes. The eye corrected for near vision will form sharper images of near objects like books or mobile phones, and blurrier images of far objects like mountains or street signs. Similarly, the eye corrected for far vision will form blurrier images of near objects and sharper images of far objects. Burge et al. , recently reported that interocular differences in optical blur, like those induced by monovision corrections, have the potential to cause large errors in estimating the distance and 3D direction of moving objects. Under some conditions, the perceptual errors may be large enough to impact public safety 5 . For example, the distance to a cyclist in cross-traffic may be overestimated by nearly 9 ft, the width of a narrow lane of traffic (Fig. ). The illusion occurs because the image in the blurrier eye is processed more quickly by a few milliseconds than the image in the sharper eye. Blur removes high spatial frequencies (i.e. fine details) from the image 6-8 , and high spatial frequencies are known to be processed more slowly . Thus, the blurry image is processed more quickly because the high frequencies in the sharp image slow its processing down 5 . For moving targets, this interocular mismatch in processing speed causes a neural disparity, which results in the misperception (see "Results"). The new illusion-the reverse Pulfrich effect-is closely related to the classic Pulfrich effect, a well-known stereomotion phenomenon that was first discovered 100 years ago. The classic Pulfrich effect is induced by an interocular difference in retinal illuminance. However, darkening the image in one eye has the opposite effect of blur 15 . The darker image is processed more slowly rather than more quickly . The response properties of neurons in both the retina and early visual cortex are thought to

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Effect of induced monocular blur on monocular and binocular visual functions
Rohit Saxena, IP Innovative Publication Pvt. Ltd.

Background and purpose: Anisometropia and surgical monovision is likely to have a detrimental impact on binocular visual functions. This study evaluates the effect of induced monocular blur in the form of a refractive defocus on visual functions and binocularity. Methods: An experimental study was conducted on 30 young emmetropic adults. Monocular myopia and hypermetropia was induced using 6 plus and minus spherical lenses in steps of 0.5 Dioptre ranging from +/-0.5DS to +/-3.00DS. Visual Acuity (LogMAR), contrast sensitivity (Pelli Robson), binocularity (Bagolini striated glasses) and stereoacuity (near Randot, distance Randot and Frisby davis Distance) were evaluated at baseline and each level of refractive defocus. Results: Induced monocular myopic shift resulted in reduction of visual acuity to 0.94 log MAR while hyperopic shift reduced visual acuity to 0.1 log MAR. Contrast sensitivity did not show a significant reduction with optical blur. Hyperopic shift did not hamper gross binocular vision unlike myopic shift where distance binocular vision was elicited only till a +2D defocus and near binocular vision till a +3D defocus. Near stereopsis deteriorated with both a hyperopic and myopic blur but was not completely lost and could be elicited even with the maximal blur. Distance randot stereopsis was lost on inducing a +2.5D blur while Frisby Davis distance stereopsis was lost at +3D blur. Induced hyperopic shift did not lead to an absolute loss of distance stereopsis. Conclusion: Binocular visual functions were significantly affected by induced monocular blur through a spherical refractive defocus. Induced myopic shift caused significantly more stereo acuity loss than induced hyperopia. Optical blur impacts distance stereoacuity to a greater extent than near.

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Reduced-aperture monovision for presbyopia and the Pulfrich effect
Dionysia Petratou

Journal of Optometry, 2012

Purpose: Monocular use of reduced-aperture optics in the form of a corneal inlay or contact lens may improve near vision of presbyopes by increasing their depth-of-focus (DOF). However, the associated induced interocular differences in retinal illuminance may cause distortion in spatial perception due to the Pulfrich effect. Methods: Three young subjects were used to explore the Pulfrich effect during reducedaperture monovision using afocal contact lenses (in the non-dominant eye) which were either opaque with a central clear aperture of 1.5, 2.5 or 3.5 mm diameter, or had an annular opaque stop of inner and outer diameters 1.5 and 4.0 mm, respectively. The two-alternative forced choice (2AFC) task of the subject was to state whether a 2 • circular spot appeared in front or behind the plane of a central cross when moved left-to-right or right-to-left. The retinal illuminance of the dominant eye was varied using neutral density (ND) filters to establish the ND value which eliminated the Pulfrich effect for each lens. Results: The Pulfrich effect was observed with all the lenses. The ND value required to null the effect decreased as the diameter of the aperture of the lenses increased. A reasonably good agreement was found between observed ND values for the different lenses and those predicted from the relative areas of the effective pupils of the two eyes. Minor discrepancies were attributed to decentration of the contact lenses with respect to the natural pupils. Conclusions: Reduced-aperture monovision generates marked Pulfrich-type distortions in spatial perception under conditions where the visual world is changing dynamically as a result of movement.

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

2020

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 dif...

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Target tracking reveals the time course of visual processing with millisecond-scale precision
Johannes Burge

2020

Image differences between the eyes can cause millisecond-scale interocular differences in processing speed. For moving objects, these differences can cause dramatic misperceptions of distance and 3D direction. Here, we develop a continuous target-tracking paradigm that shows these tiny differences in the speed of visual processing are preserved in the movement dynamics of the hand. Human observers continuously tracked a target stimulus with various luminance differences across the eyes as it underwent Brownian motion in the horizontal plane. We show that suitable analysis recovers the time course of the visuomotor response, and comparisons across luminance conditions reveal the temporal evolution of visual processing differences between the eyes. Additionally, using a direct within-observer comparison, we show that target tracking and traditional psychophysics provide scalar estimates of interocular delays that agree on average to within a fraction of a millisecond. Thus, target tra...

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Contact lenses, the reverse Pulfrich effect, and anti-Pulfrich monovision corrections
Johannes Burge

Scientific Reports, 2020

Interocular differences in image blur can cause processing speed differences that lead to dramatic misperceptions of the distance and three-dimensional direction of moving objects. This recently discovered illusion—the reverse Pulfrich effect—is caused by optical conditions induced by monovision, a common correction for presbyopia. Fortunately, anti-Pulfrich monovision corrections, which darken the blurring lens, can eliminate the illusion for many viewing conditions. However, the reverse Pulfrich effect and the efficacy of anti-Pulfrich corrections have been demonstrated only with trial lenses. This situation should be addressed, for clinical and scientific reasons. First, it is important to replicate these effects with contact lenses, the most common method for delivering monovision. Second, trial lenses of different powers, unlike contacts, can cause large magnification differences between the eyes. To confidently attribute the reverse Pulfrich effect to interocular optical blur ...

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