Stimuli Characteristics and Psychophysical Requirements for Visual Training in Amblyopia: A Narrative Review.

Carlos J Hernández-Rodríguez,Luis Leal-Vega,Juan F Arenillas,David P Piñero,María Begoña Coco-Martín,Ainhoa Molina-Martín,Dolores De Fez,León Morales-Quezada

doi:10.3390/jcm9123985

Abstract

Active vision therapy using perceptual learning and/or dichoptic or binocular environments has shown its potential effectiveness in amblyopia, but some doubts remain about the type of stimuli and the mode and sequence of presentation that should be used. A search was performed in PubMed, obtaining 143 articles with information related to the stimuli used in amblyopia rehabilitation, as well as to the neural mechanisms implied in such therapeutic process. Visual deficits in amblyopia and their neural mechanisms associated are revised, including visual acuity loss, contrast sensitivity reduction and stereopsis impairment. Likewise, the most appropriate stimuli according to the literature that should be used for an efficient rehabilitation of the amblyopic eye are described in detail, including optotypes, Gabor’s patches, random-dot stimuli and Vernier’s stimuli. Finally, the properties of these stimuli that can be modified during the visual training are discussed, as well as the psychophysical method of their presentation and the type of environment used (perceptual learning, dichoptic stimulation or virtual reality). Vision therapy using all these revised concepts can be an effective option for treating amblyopia or accelerating the treatment period when combining with patching. It is essential to adapt the stimuli to the patient’s individual features in both monocular and binocular training.

Highlights

Amblyopia is a visual developmental disorder consisting of a reduced best-corrected visual acuity in one or, rarely, both eyes without the presence of any ocular pathology
The prevalence of amblyopia in childhood is approximately between 1 and 3%, these values differ among authors [3,4]
Amblyopic eyes showed worse neural adaptation in V1, V2, V3, V3a, Vp and V4, that is, a reduced cortical automation after a repeated visual task compared with fellow eyes, and a decreased neural response assessed by functional magnetic resonance imaging [6] as well as a worse effective connectivity between the implied brain regions, which is correlated with the reduced visual acuity [7]

Summary

Introduction

Amblyopia is a visual developmental disorder consisting of a reduced best-corrected visual acuity in one or, rarely, both eyes without the presence of any ocular pathology. Less common is deprivation amblyopia, which is caused by a pathology that avoids the eye stimulation during childhood and causes a severe visual deficit [1,2]. The prevalence of amblyopia in childhood is approximately between 1 and 3%, these values differ among authors [3,4]. The loss of visual acuity and the presence of many other monocular and binocular visual deficits are the consequence of the anomalies in the visual pathway of the amblyopes, mainly in the striate and extra-striate cortex [5]. Amblyopic eyes showed worse neural adaptation in V1, V2, V3, V3a, Vp and V4, that is, a reduced cortical automation after a repeated visual task compared with fellow eyes, and a decreased neural response assessed by functional magnetic resonance imaging (fMRI) [6] as well as a worse effective connectivity between the implied brain regions, which is correlated with the reduced visual acuity [7]

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