Static Aspects of Accommodation in Human Amblyopia

Ciuffreda, Kenneth J.; Hokoda, Steven C.; Hung, George K.; Semmlow, John L.; Selenow, Arkady

doi:10.1097/00006324-198306000-00004

Cited by 92 publications

(90 citation statements)

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“…All these tasks require visual integration across space. Unevenly distributed impairments in spatial integration (due, perhaps, to local undersampling) may give the psychophysical appearance of topographical jitter, resulting in the localization biases observed in some strabismic amblyopes (1). Although most of our results are consistent with the idea of topographical jitter, a more cogent explanation can be found in terms of a higher order deficit of spatial integration.…”

Section: Discussionsupporting

confidence: 60%

“…A mblyopia is a developmental visual impairment which cannot be eliminated by optical refraction (glasses), and has no clear organic cause, such as glaucoma, damage to the optic nerve, or damage to the retina (1). Amblyopia can be induced in animals by visual deprivation during critical periods of development, and is in these cases associated with specific neurophysiological and psychophysical abnormalities in the representation of visual space in the primary visual cortex (2).…”

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confidence: 99%

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Amblyopes see true alignment where normal observers see illusory tilt

Popple

Levi

2000

Proc. Natl. Acad. Sci. U.S.A.

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Amblyopia (''lazy eye'') is an impairment in visual acuity resulting from abnormal neural development in the visual cortex. We tested the responses of ten amblyopic and six normal observers to illusions of perceived orientation in textures of Gabor patches: the ''Fraser illusion,'' the ''phase illusion,'' and a ''tilted chain'' illusion. The illusory tilt of the stimulus rows was matched by actual tilt in the opposite direction by using the method of constant stimuli. Amblyopes showed a significant increase in the Fraser illusion, a decrease in the phase illusion, and a reversal of the tilted chain illusion. Amblyopic performance could be simulated in normal observers by reducing the length of the rows. These results can be modeled by a theory which places the neural abnormality in amblyopia at the level of second stage grouping processes. Additionally, the illusions might be useful in the early diagnosis of amblyopia without the need for prior refractive correction.

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Section: Discussionsupporting

confidence: 60%

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confidence: 99%

Amblyopes see true alignment where normal observers see illusory tilt

Popple

Levi

2000

Proc. Natl. Acad. Sci. U.S.A.

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“…Because spatial filters in the visual cortex filter any incoming visual information, they are expected also to limit performance on letter identification (34). In particular, the increased lateral inhibition described above is expected to degrade letter identification (crowding effect) when the letter to be identified is surrounded by other letters, as in standard VA tests (4,27). Thus, the practice-induced reduction of inhibitory interactions is expected to improve VA.…”

Section: Resultsmentioning

confidence: 99%

“…No treatment is currently available for adults with amblyopia (4,(10)(11)(12). In young children, amblyopia is treated primarily with eye-patching, forcing the ''lazy eye'' to function by covering the eye that sees better.…”

Section: Discussionmentioning

confidence: 99%

Improving vision in adult amblyopia by perceptual learning

Polat

Ma-Naim

Belkin

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

393

401

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Practicing certain visual tasks leads, as a result of a process termed ''perceptual learning,'' to a significant improvement in performance. Learning is specific for basic stimulus features such as local orientation, retinal location, and eye of presentation, suggesting modification of neuronal processes at the primary visual cortex in adults. It is not known, however, whether such low-level learning affects higher-level visual tasks such as recognition. By systematic low-level training of an adult visual system malfunctioning as a result of abnormal development (leading to amblyopia) of the primary visual cortex during the ''critical period,'' we show here that induction of low-level changes might yield significant perceptual benefits that transfer to higher visual tasks. The training procedure resulted in a 2-fold improvement in contrast sensitivity and in letter-recognition tasks. These findings demonstrate that perceptual learning can improve basic representations within an adult visual system that did not develop during the critical period.A mblyopia is characterized by several functional abnormalities in spatial vision (for reviews see refs. 1-4), including reductions in visual acuity (VA), contrast-sensitivity function (CSF), and vernier acuity as well as spatial distortion (5), abnormal spatial interactions (6, 7), and impaired contour detection (8,9). In addition, amblyopic individuals suffer from binocular abnormalities such as impaired stereoacuity and abnormal binocular summation. The visual deficiencies are thought to be irreversible after the first decade of life (10-12), by which time the developmental maturation window has been terminated. The loss of vision is thought to result from abnormal operation of the neuronal network within the primary visual cortex, particularly of orientation-selective neurons and their interactions (13). The perceptual learning procedure described in this study was designed to train this network by efficiently stimulating these neuronal populations and effectively promoting their spatial interactions.Spatial interactions in human vision can be probed by contrast detection of a localized target in the presence of flankers (Fig. 1). These experiments show that the contrast threshold of a foveal Gabor signal (GS) is reduced in the presence of cooriented and coaligned (collinear) high-contrast GS flankers (14-18). The excitatory interaction is range-dependent and is maximal for target-flanker separation of approximately three times the GS wavelength. Smaller separations can raise the target threshold, depending on flanker contrast and phase (19). Singleunit recordings suggest that the underlying mechanisms reside within the primary visual cortex (20,21). Neuronal responses in the visual cortex are tuned for location, orientation, and spatial frequency. Recent evidence from studies in the cat and the monkey (20,(22)(23)(24)(25) shows that neuronal responses in the primary visual cortex are modulated by remote image parts, with both excitatory and inhibitory effects observ...

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“…It affects about 3% of the population (Ciuffreda, Levi, and Selenow, 1991;McKee, Levi, and Movshon, 2003;Simmers, Ledgeway, Hess, and McGraw, 2003). Conventional wisdom on visual development suggests that spatial vision becomes hardwired after a critical period, usually around 6-8 years of age (Berardi, Pizzorusso, Ratto, and Maffei, 2003); The amblyopic visual system is generally thought to be fully (though erroneously) developed by age eight and therefore no longer subject to therapeutic modifications.…”

Section: Applicationsmentioning

confidence: 99%

Visual Perceptual Learning

SpringerReference

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Perceptual learning refers to the phenomenon that practice or training in perceptual tasks often substantially improves perceptual performance. Often exhibiting stimulus or task specificities, perceptual learning differs from learning in the cognitive or motor domains. Research on perceptual learning reveals important plasticity in adult perceptual systems, and as well as the limitations in the information processing of the human observer. In this article, we review the behavioral results, mechanisms, physiological basis, computational models, and applications of visual perceptual learning.

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Static Aspects of Accommodation in Human Amblyopia

Cited by 92 publications

References 0 publications

Amblyopes see true alignment where normal observers see illusory tilt

Amblyopes see true alignment where normal observers see illusory tilt

Improving vision in adult amblyopia by perceptual learning

Visual Perceptual Learning

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