Binocular summation in the fovea and peripheral field of anisometropic amblyopes

Pardhan, Shahina; Whitaker, A.J.T.

doi:10.1076/0271-3683(200001)2011-hft035

Cited by 28 publications

(9 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We found that the extent of ocular dominance bias varied with both field location and hemisphere, with the foveal sites and ipsilateral hemisphere generally showing the largest bias. This finding is consistent with human psychophysical data showing larger sensitivity losses in amblyopic fovea (Hess & Pointer, 1985, Pardhan & Whitaker, 2000, Sireteanu & Fronius, 1981, Thomas, 1978) and further suggests a specific weakness of the cortical representation of the temporal retina of the amblyopic eye.…”

Section: Discussionsupporting

confidence: 90%

Population representation of visual information in areas V1 and V2 of amblyopic macaques

et al. 2015

View full text Add to dashboard Cite

Amblyopia is a developmental disorder resulting in poor vision in one eye. The mechanism by which input to the affected eye is prevented from reaching the level of awareness remains poorly understood. We recorded simultaneously from large populations of neurons in the supragranular layers of areas V1 and V2 in 6 macaques that were made amblyopic by rearing with artificial strabismus or anisometropia, and 1 normally reared control. In agreement with previous reports, we found that cortical neuronal signals driven through the amblyopic eyes were reduced, and that cortical neurons were on average more strongly driven by the non-amblyopic than by the amblyopic eyes. We analyzed multiunit recordings using standard population decoding methods, and found that visual signals from the amblyopic eye, while weakened, were not degraded enough to explain the behavioral deficits. Thus additional losses must arise in downstream processing. We tested the idea that under monocular viewing conditions, only signals from neurons dominated by – rather than driven by – the open eye might be used. This reduces the proportion of neuronal signals available from the amblyopic eye, and amplifies the interocular difference observed at the level of single neurons. We conclude that amblyopia might arise in part from degradation in the neuronal signals from the amblyopic eye, and in part from a reduction in the number of signals processed by downstream areas.

show abstract

Section: Discussionsupporting

confidence: 90%

Population representation of visual information in areas V1 and V2 of amblyopic macaques

et al. 2015

View full text Add to dashboard Cite

show abstract

“…11, 14, 15, 20, 21, 28 However, a growing body of evidence suggests that the visual system in amblyopes may retain structural binocularity, despite being functionally monocular due to suppression from the fellow eye. 4 For example, when visual acuity and contrast are balanced between the eyes by diminishing luminance for better eye, binocular summation improves to normal in strabismic amblyopes.…”

Section: Introductionmentioning

confidence: 99%

Decreased Binocular Summation in Strabismic Amblyopes and Effect of Strabismus Surgery

et al. 2017

View full text Add to dashboard Cite

Purpose: Binocular summation (BiS) occurs when binocular visual function surpasses that of the better eye alone. We sought to evaluate whether strabismic amblyopia reduces BiS more than strabismus alone, and determine whether BiS improves in strabismic amblyopes after strabismus surgery. Methods: We prospectively recruited 15 patients with strabismic amblyopia who then underwent strabismus surgery. Thirty age-matched normal subjects and 30 non-amblyopic strabismic patients served as controls. Subjects underwent binocular and monocular visual acuity testing on high-contrast Early Treatment Diabetic Retinopathy Study (ETDRS) as well as 2.5% and 1.25% Sloan low contrast acuity (LCA) charts. BiS was calculated as the difference between better eye and binocular scores. Results: Strabismic amblyopes and strabismic controls did not significantly differ in preoperative BiS, but both had subnormal BiS preoperatively on LCA charts. Among 11 strabismic amblyopes with preoperative and postoperative BiS measurements, average postoperative BiS was not significantly different from preoperative. Improved LCA BiS postoperatively occurred in some patients and was associated with measurable preoperative stereoacuity (p = 0.02), older age at strabismus onset (p = 0.02), and larger preoperative angle of strabismus (p = 0.0043). Conclusions: In this preliminary study, strabismic amblyopes experienced subnormal BiS, but amblyopia generally did not further impair BiS beyond that due to strabismus alone. Some strabismic amblyopes experienced improved low-contrast BiS after strabismus surgery. This suggests that further investigations in larger groups of patients should be undertaken to analyze a previously unrecognized functional benefit of strabismus surgery in strabismic amblyopes.

show abstract

“…The most common risk factors for developing amblyopia are anisometropia (unequal refractive error in the two eyes), strabismus (misalignment of visual axes) and another form of deprivation (e.g., congenital cataract) early in life (Kiorpes and McKee, 1999 ; Roper-Hall, 2007 ). In the case of anisometropic amblyopia, peripheral retina is generally normal (Yu et al, 1998 ; Pardhan and Whitaker, 2000 ), and spatial vision deficits are the consequence of chronic blur in the area of central retina during sensitive period for development of visual acuity (see Daw, 1998 ). Anisometropia becomes clinically significant when its magnitude reaches approximately 1 D in either one or both meridians (Benjamin, 2006 ).…”

Section: Introductionmentioning

confidence: 99%

“…Taking all into consideration, the central retina has a dominant effect on observed visual deficits in subjects with anisometropic amblyopia (Yu et al, 1998 ; Pardhan and Whitaker, 2000 ), thus we expect that the loss of physiological function of foveal vision in these individuals may affect specifically saccades in terms of their spatial and temporal properties during saccade delayed task.…”

Section: Introductionmentioning

confidence: 99%

The amblyopic eye in subjects with anisometropia show increased saccadic latency in the delayed saccade task

Perdziak

Witkowska

Gryncewicz

et al. 2014

Front. Integr. Neurosci.

View full text Add to dashboard Cite

The term amblyopia is used to describe reduced visual function in one eye (or both eyes, though not so often) which cannot be fully improved by refractive correction and explained by the organic cause observed during regular eye examination. Amblyopia is associated with abnormal visual experience (e.g., anisometropia) during infancy or early childhood. Several studies have shown prolongation of saccadic latency time in amblyopic eye. In our opinion, study of saccadic latency in the context of central vision deficits assessment, should be based on central retina stimulation. For this reason, we proposed saccade delayed task. It requires inhibitory processing for maintaining fixation on the central target until it disappears—what constitutes the GO signal for saccade. The experiment consisted of 100 trials for each eye and was performed under two viewing conditions: monocular amblyopic/non-dominant eye and monocular dominant eye. We examined saccadic latency in 16 subjects (mean age 30 ± 11 years) with anisometropic amblyopia (two subjects had also microtropia) and in 17 control subjects (mean age 28 ± 8 years). Participants were instructed to look at central (fixation) target and when it disappears, to make the saccade toward the periphery (10°) as fast as possible, either left or the right target. The study results have proved the significant difference in saccadic latency between the amblyopic (mean 262 ± 48 ms) and dominant (mean 237 ± 45 ms) eye, in anisometropic group. In the control group, the saccadic latency for dominant (mean 226 ± 32 ms) and non-dominant (mean 230 ± 29 ms) eye was not significantly different. By the use of LATER (Linear Approach to the Threshold with Ergodic Rate) decision model we interpret our findings as a decrease in accumulation of visual information acquired by means of central retina in subjects with anisometropic amblyopia.

show abstract

Binocular summation in the fovea and peripheral field of anisometropic amblyopes

Abstract: Results are discussed in terms of tolerance to interocular sensitivity differences in the periphery and selective losses in cortical cells.

Cited by 28 publications

References 27 publications

Population representation of visual information in areas V1 and V2 of amblyopic macaques

Population representation of visual information in areas V1 and V2 of amblyopic macaques

Decreased Binocular Summation in Strabismic Amblyopes and Effect of Strabismus Surgery

The amblyopic eye in subjects with anisometropia show increased saccadic latency in the delayed saccade task

Contact Info

Product

Resources

About