Binocular summation in normal and stereoblind humans

doi:10.1016/S0042-6989(77)80004-7

Vision Research

Volume 17, Issue 6, 1977, Pages 691-695

https://doi.org/10.1016/S0042-6989(77)80004-7 Get rights and content

Abstract

Monocular and binocular contrast thresholds were measured over a range of spatial frequencies in normal and stereoblind observers. Unlike normal individuals, whose binocular thresholds were consistently lower than monocular, stereoblind individuals were no better with two eyes than with one. These results suggest that stereopsis and binocular summation are mediated by a common neural mechanism.

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Intensive monocular perceptual learning can improve visual acuity, contrast sensitivity, and vernier acuity in the amblyopic eye in adults with amblyopia. It is however not clear how much monocular training can enhance binocular visual functions. In the current study, we aimed to evaluate effects of monocular training on a variety of binocular functions. Nineteen anisometropic amblyopes (18.5 ± 1.26 yrs, mean ± s.e.) were trained in a grating contrast detection task near each individual’s cutoff spatial frequency for 6–10 days (630 trials/day). Visual acuity, stereoacuity, monocular and binocular contrast sensitivity functions (CSF), binocular phase combination and binocular rivalry were tested before and after training. Although monocular training can improve visual acuity and contrast sensitivity and eye dominance of the amblyopic eye, the magnitudes of improvements did not correlate with each other; the impact of monocular training on binocular phase combination was not significant. The results strongly suggest that structured monocular and binocular training is needed to fully recover deficient visual functions in anisometropic amblyopia.
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Citation Excerpt :
Previous studies have suggested a relationship between stereopsis and binocular summation; one investigation demonstrated that stereoblind subjects had significantly less binocular summation in pupillary response than normal subjects.10 As well, a decrease in binocular summation in stereoblind individuals was demonstrated using visual evoked potentials11 and contrast thresholds.2 These data, along with the general understanding that binocular summation is a cortical function, suggest that stereopsis and binocular summation may be mediated by common neural pathways.2
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setting: Stein Eye Institute, University of California Los Angeles. patient population: Pediatric strabismic patients who underwent strabismus surgery between 2010 and 2015. observation procedures: Early Treatment Diabetic Retinopathy Study visual acuity, Sloan low-contrast acuity (LCA, 2.5% and 1.25%), and Randot stereoacuity 2 months following surgical correction of strabismus. main outcome measures: The relationship between binocular summation (BiS), calculated as the difference between the binocular visual acuity score and that of the better eye, and stereoacuity.
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These findings demonstrate that stereopsis and binocular summation are significantly correlated in patients who have undergone surgical correction of strabismus.
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2013, Journal of AAPOS
Citation Excerpt :
All participants provided full written informed consent. Although previous investigators have suggested that patients with amblyopia do not exhibit binocular summation at high spatial frequencies and therefore do not possess binocular capabilities,8-11 we have shown more recently that once high spatial frequency stimuli shown to each eye are equated in terms of threshold contrast, normal levels of binocular summation can occur.12 It would appear, therefore, that the contrast sensitivity deficit affecting the amblyopic eye has obscured the important fact that patients with amblyopia still possess functional binocular summation mechanisms.
The current approach to the treatment of amblyopia is problematic for a number of reasons. First, it promotes recovery of monocular vision but because it is not designed to promote binocularity, its binocular outcomes often are disappointing. Second, compliance is poor and variable. Third, the effectiveness of the treatment is thought to decrease with increasing age. We discuss 2 new approaches aimed at recovering visual function in adults with amblyopia. The first is a binocular approach to amblyopia treatment that is showing promise in initial clinical studies. The second is still in development and involves the use of well-established noninvasive brain stimulation techniques to temporarily alter the balance of excitation and inhibition in the visual cortex.
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View full text

Binocular summation in normal and stereoblind humans

Abstract

Vision Res.

Vision Res.

Vision Res.

Vision Res.

Movement aftereffects contingent on binocular disparity

Perception

Critical period for the development of human binocular vision

Science

The neural mechanism of binocular depth perception

J. Physiol., Lond.

Binocular depth discrimination depends on orientation

Percept. Psychophys.

Interocular transfer of adaptation to spatial frequency during retinal ischaemia

Nature, New Biol.

The psychophysical inquiry into binocular summation

Percept. Psychophys.

Spatial frequency- and orientation-specificity of binocular neurones in the human visual system

Expl Brain Res.

On the existence of neurones in the human visual system selectively sensitive to the orientation and size of retinal images

J. Physiol., Lond.

Evidence for disparity detecting neurons in the human visual system

J. Physiol., Lond.

Monocular versus binocular visual acuity

Nature, Lond.

Optical and retinal factors affecting visual resolution

J. Physiol, Lond.