The amblyopic deficit for 2nd order processing: Generality and laterality

Gao, Yi; Reynaud, Alexandre; Tang, Yong; Feng, Lei; Zhou, Yifeng; Hess, Robert F.

doi:10.1016/j.visres.2014.10.020

Cited by 15 publications

(19 citation statements)

References 53 publications

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“…5b), slightly lower than reported under purely monocular conditions. 24 The cutoff frequency f c of their amblyopic eye (see calculation in Methods and Table 1) is, in general, much lower than that of their fellow eye, as expected. 5,6 This can be observed in Figure 5b.…”

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confidence: 73%

“…22 The use of this method for amblyopic populations has previously been validated. 23,24 The frequency range was truncated from 0.35 to 6.87 cyc/deg. The initial gain prior was set to 100, the peak frequency prior set to 2 cyc/deg, the bandwidth prior set to 3 octaves, and the truncation prior set to 0.5.…”

mentioning

confidence: 99%

“…The accuracy of the qCSF method for amblyopes has already been validated. 23,24 The sensitivities for the fellow eye show a normal pattern with an average peak sensitivity of approximately 40 at …”

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confidence: 99%

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Is Suppression Just Normal Dichoptic Masking? Suprathreshold Considerations

Reynaud

Hess

2016

Invest. Ophthalmol. Vis. Sci.

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PURPOSE. Amblyopic patients have a deficit in visual acuity and contrast sensitivity in their amblyopic eye as well as suppression of the amblyopic eye input under binocular viewing conditions. In this study we wanted to assess the origin of the amblyopic suppression by studying the contrast perception of the amblyopic eye at suprathreshold levels under binocular and monocular viewing.METHODS. Using a suprathreshold contrast matching task in which the reference and target stimuli were presented to different eyes either simultaneously or successively, we measured interocular contrast matching in 10 controls and 11 amblyopes (mean age 35 6 15; 5 strabismics; 3 anisometropes; 3 mixed). This was then used as an index of the binocular balance across spatial frequency and compared against the contrast sensitivity ratio measured with the same stimuli.RESULTS. We observed that binocular matching becomes more imbalanced at high spatial frequency for amblyopes, compared with controls; that this imbalance did not depend in either group on whether the stimuli were presented simultaneously or successively; and that for both modes of presentation the matching balance correlates well with the interocular contrast sensitivity ratio (mean correlation coefficient of the slopes R ¼ 0.7125). CONCLUSIONS.The results from our amblyopes show comparable losses of contrast perception at and above threshold under these binocular viewing conditions across a wide spatial frequency range, much stronger than that observed for our controls. This occurs under conditions in which there should be no dichoptic masking. Furthermore, the matching contrast could be well predicted by the monocular contrast sensitivity. Altogether, this suggests that amblyopic suppression cannot be explained by normal dichoptic masking but rather an attenuation of the input.Keywords: interocular matching, amblyopia, qCSF, contrast constancy, suppression A mblyopia involves a loss of monocular vision and a suppression of the amblyopic eye's function under binocular viewing. There is debate about the causal relationship between these two factors. One possibility is that the suppression seen in amblyopia is a consequence of combining normal dichoptic masking with elevated contrast threshold in the amblyopic eye. Dichoptic masking depends on the level of suprathreshold contrast, so an elevated threshold in one eye (e.g., the amblyopic eye) would automatically result in imbalanced masking at all contrast levels, such that one eye (e.g., the fellow fixing eye) will always dominate over the other. We refer to this as the threshold hypothesis, as implemented by the offset subtraction model (see Appendix) where the primary deficit is the amblyopia and the secondary consequence is the binocular dysfunction.1,2 An alternate explanation is that the suppression results from anomalously large dichoptic inhibition of the amblyopic eye's input by the fellow fixing eye's input that in the long term results in a contrast threshold elevation in the amblyopic eye. We refer to this as the...

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Is Suppression Just Normal Dichoptic Masking? Suprathreshold Considerations

Reynaud

Hess

2016

Invest. Ophthalmol. Vis. Sci.

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“…Considering the strabismic amblyopia, reduced cytochrome oxidase, indicating decrease in cortical activity, was found in cortical layers 2/3/4A and 4B compared to layers 4C 5/6 of the amblyopic eye (Adams, Economides, & Horton, 2015) and could be related with our imaging results. There are also recent evidences that the contralateral non-amblyopic eye also have functional impairments in strabismic amblyopia (Gao et al, 2014). It is important to take in mind that the lack of cortical asymmetry in strabismus suggests that a different developmental process occurs in those patients than in the anisometropic amblyopia patients.…”

Section: Functional Magnetic Resonance Imagingmentioning

confidence: 99%

Strabismic amblyopia disrupts the hemispheric asymmetry for spatial stimuli in cortical visual processing

Costa

Cunha

Marques

2016

British Journal of Visual Impairment

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Hemispheric asymmetry in processing visual stimuli was assessed in anisometropic and strabismic amblyopia and control subjects. Measurements of contrast sensitivity for low and high spatial frequencies were performed psychophysically and tested under functional magnetic resonance imaging (fMRI) using a stimulus configuration that generates measurements for each temporal and nasal hemifield. The fMRI and the psychophysics results showed a marked hemispheric asymmetry in processing spatial frequencies for normal and anisometropic adults, in which low spatial frequencies were mainly processed in the left visual field -right hemisphere (LVF-RH: 0.3 cycles per degree [cpd]; F = 12.548; p = .002) and the high spatial frequencies were predominating processed in the right visual field -left hemisphere (RVF-LH: 2.0 cpd; F = 4.582; p = .021 and 8.3 cpd; F = 8.561; p = .001). No asymmetry was present in the amblyopic and the fellow eye of the strabismic amblyopia subjects. We conclude that the developmental organization of visual cortex in strabismic amblyopia is impaired differently from what happens in the anisometropic amblyopia and support the impairment of high-level visual-related functions observed in strabismic children.

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“…This is evident in the performance of patients with amblyopia on psychophysical tasks that are thought to require processes supported by extrastriate visual areas. Using this approach, Gao et al (2015) employed a range of second-order stimuli (defined by textural cues rather than luminance boundaries) designed to target either the dorsal or ventral cortical streams. When viewing with the amblyopic eye, patients exhibited deficits across a wide range of second-order stimuli implicating both dorsal and ventral processing stream deficits.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 99%