Variability of Accommodation during Steady Fixation at Various Levels of Illuminance*

Alpern, Mathew

doi:10.1364/josa.48.000193

Cited by 99 publications

(32 citation statements)

References 7 publications

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“…This finding thus rules out eye movements (e.g., saccades and microsaccades) as a direct cause of the illusion, as well as any direct contribution from accommodation fluctuations (Alpern, 1958;Campbell et al, 1959;Kotulak and Schor, 1986;Winn and Gilmartin, 1992;Gray et al, 1993), small changes of the shape of the lens that distort the retinal image. This does not preclude, however, an indirect role for eye movements (or accommodation responses) in the flickering effect (e.g., by modulating the phase or amplitude of ␣ rhythms in such a way that would eventually result in the perception of illusory flicker).…”

Section: Is Retinal Motion Of the Wheel Necessary?mentioning

confidence: 94%

The Flickering Wheel Illusion: When α Rhythms Make a Static Wheel Flicker

Sokoliuk

VanRullen

2013

J. Neurosci.

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␣ oscillations (8 -14 Hz) greatly influence brain activity, yet we generally do not experience them consciously: the world does not appear to oscillate. Dedicated strategies must exist in the brain to prevent these oscillations from disrupting normal processing. Could suitable stimuli fool these strategies and lead to the conscious experience of our own brain oscillations? We describe and explore a novel illusion in which the center of a static wheel stimulus (with 30 -40 spokes) is experienced as flickering when viewed in the visual periphery. The key feature of this illusion is that the stimulus fluctuations are experienced as a regular and consistent flicker, which our human observers estimated at ϳ9 Hz during a psychophysical matching task. Correspondingly, the occipital ␣ rhythm of the EEG was the only oscillation that showed a time course compatible with the reported illusion: when ␣ amplitude was strong, the probability of reporting illusory flicker increased. The peak oscillatory frequency for these flicker-induced modulations was significantly correlated, on a subject-bysubject basis, with the individual ␣ frequency measured during rest, in the absence of visual stimulation. Finally, although the effect is strongest during eye movements, we showed that stimulus motion relative to the retina is not necessary to perceive the illusion: the flicker can also be perceived on the afterimage of the wheel, yet by definition this afterimage is stationary on the retina. We conclude that this new flickering illusion is a unique way to experience the ␣ rhythms that constantly occur in the brain but normally remain unnoticed.

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Section: Is Retinal Motion Of the Wheel Necessary?mentioning

confidence: 94%

The Flickering Wheel Illusion: When α Rhythms Make a Static Wheel Flicker

Sokoliuk

VanRullen

2013

J. Neurosci.

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“…Several earlier researchers had reported myopia under very low luminance (Otero, 1951 ;Campbell & Primrose, 1953 ;Alpern, 1958); when vision was 'fogged' through the use of strong plus" lenses (Reese & Fry, 1941, Heath, 1956, or by reduction of stimulus contrast (Luckiesch & Moss, 1940;Heath, 1956;Westheimer, 1957). However, since most of these experiments involved either small subject samples or limited test conditions, the wide variation in the amount of myopia reported in these studies was difficult to interpret.…”

Section: Empirical Studies Of the Dark-focusmentioning

confidence: 93%

New evidence for the intermediate position of relaxed accommodation

1978

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Experimental evidence is presented that the focus of the eye tends to return passively to an individually characteristic intermediate resting position or dark-focus whenever (1) the stimulus to accommodation is degraded or (2) when the quality of the image is independent of focus. Based on measurements of the dark-focus with a laser optometer, it is possible to predict the magnitude of night, empty field, and instrument myopia on an individual basis. The role of the intermediate dark-focus as a factor in accommodation also provides an explanation for the paradoxical variation of visual acuity with observation distance. Applications to night myopia and night driving are described, and implications for clinical practice are discussed.

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“…Accommodation operates to maximise retinal-image contrast [23][24][25][26][27][28][29][30][31][32] . MacKenzie et al 18 analysed the retinal-image contrast that results from viewing depth-filtered images and showed that in many cases the peak retinal-image contrast is achieved by focusing at or near the focal distance simulated using depth filtering.…”

Section: Accommodation and Vergence Responses To Depth-filtered Imagesmentioning

confidence: 99%

Real-world stereoscopic performance in multiple-focal-plane displays: How far apart should the image planes be?

2012

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Conventional stereoscopic displays present conflicting stimuli to vergence and accommodation, causing fatigue, discomfort, and poor stereo depth perception. One promising solution is 'depth filtering', in which continuous variations in focal distance are simulated by distributing image intensity across multiple focal planes. The required image-plane spacing is a critical parameter, because there are constraints on the total number that can be used. Depth-filtered images have been shown to support continuous and reasonably accurate accommodation responses with 1.1 dioptre (D) imageplane spacings. However, retinal contrast is increasingly attenuated with increasing image-plane separation. Thus, while such stimuli may eliminate the vergence-accommodation conflict, they may also unacceptably degrade stereoscopic depth perception. Here we measured stereoacuity, and the time needed for stereoscopic fusion, for real targets and depthfiltered approximations to the same stimuli (image-plane spacings of 0.6, 0.9 and 1.2 D). Stereo fusion time was reasonably consistent across conditions. Stereoacuity for depth-filtered stimuli was only slightly poorer than for real targets with 0.6 D image-plane separation, but deteriorated rapidly thereafter. Our results suggest that stereoscopic depth perception, not accommodation and vergence responses, is the limiting factor in determining acceptable image-plane spacing for depth-filtered images. We suggest that image-plane spacing should ideally not exceed ~0.6 D.

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Variability of Accommodation during Steady Fixation at Various Levels of Illuminance*

Cited by 99 publications

References 7 publications

The Flickering Wheel Illusion: When α Rhythms Make a Static Wheel Flicker

The Flickering Wheel Illusion: When α Rhythms Make a Static Wheel Flicker

New evidence for the intermediate position of relaxed accommodation

Real-world stereoscopic performance in multiple-focal-plane displays: How far apart should the image planes be?

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