Steady-State Contrast Response Functions Provide a Sensitive and Objective Index of Amblyopic Deficits

Abstract

We suggest that SSVEPs offer a sensitive and objective measure of the ocular imbalance in amblyopia and could be used to assess the efficacy of amblyopia therapies currently under development.

Evidence for an Optimal Algorithm Underlying Signal Combination in Human Visual Cortex

“…A natural example for binocular vision is amblyopia, in which the amblyopic eye's responses are both weaker (i.e. suppressed) (Baker et al 2008, 2015) and noisier (Levi and Klein 2003; Baker et al 2008) than those of the fellow eye. Previously, the increased noise has been considered secondary to the suppression.…”

Covert spatial attention is functionally intact in amblyopic human adults

“…Rather than a single clinical malady with a specific organic cause, it can arise from any condition that prevents one or both eyes from focusing clearly or from having a normal binocular interaction during a critical period, which manifests in the stunted development of early visual cortex (Daw, 1998). The amblyopic eye has impaired contrast sensitivity relative to neurotypical observers (Baker, Simard, Saint-Amour, & Hess, 2015; Kiorpes, 2006; Levi, 2006; McKee, Levi, & Movshon, 2003), and even the fellow eye of amblyopes has degraded contrast sensitivity compared to the eyes of neurotypical observers (Chatzistefanou et al, 2005; Koskela, 1986; Leguire, Rogers, & Bremer, 1990). Amblyopia is often categorized into four subtypes, depending on etiology: (a) strabismic, or “lazy eye,” wherein the brain suppresses visual input from a deviated eye to prevent diplopia; (b) anisometropic, caused by a large interocular difference in refractive error; (c) deprivation, which emerges when there is a literal interruption of visual input, often due to congenital cataracts, ptosis, or corneal haziness; and (d) mixed, in which the amblyope suffers from a combination of one or more of these conditions (Levi, 2006; Levi & Carkeet, 1993; von Noorden, 1990; von Noorden & Crawford, 1978).…”

The feature extraction and estimation of a steady-state visual evoked potential by the Karhunen-Loeve expansion

“…A component model, which is described in [1], represents the SSVEP as the sum of three components: primary, secondary, and rhyth- A contrast response function is used by the authors of [2] for amblyopia diagnostics. The maximum amplitude of the evoked potentials of healthy people should be growing at changing the contrast of the stimulation source of the visual analyzer.…”

“…Consequently, the field of using the SSVEP is not limited to ophthalmological problems (assessment of visual acuity, an injury of the brain visual centers, optic neuritis, amblyopia, etc. [2]), but it is used to solve problems of cognitive (assessment of visual attention, working memory, and binocular vision [3]) and clinical (schizophrenia, autism, epilepsy, depression, migraine [4]) neurosciences, brain-computer interfaces [5], and neuromarketing [6]. Research on the SSVEP to use it further in the information technology of the ophthalmological diagnostics is an essential problem as its solving contributes to detailed visual analyzer research and appropriate complex treatment.…”