Can perceptual learning be used to treat amblyopia beyond the critical period of visual development?

Abstract

Background: Amblyopia presents early in childhood and affects approximately 3% of western populations. The monocular visual acuity loss is conventionally treated during the 'critical periods' of visual development by occluding or penalising the fellow eye to encourage use of the amblyopic eye. Despite the measurable success of this approach in many children, substantial numbers of people still suffer with amblyopia later in life because either they were never diagnosed in childhood, did not respond to the original treatment, the amblyopia was only partially remediated, or their acuity loss returned after cessation of treatment. Purpose: In this review, we consider whether the visual deficits of this largely overlooked amblyopic group are amenable to conventional and innovative therapeutic interventions later in life, well beyond the age at which treatment is thought to be effective. Recent findings: There is a considerable body of evidence that residual plasticity is present in the adult visual brain and this can be harnessed to improve function in adults with amblyopia. Perceptual training protocols have been developed to optimise visual gains in this clinical population. Results thus far are extremely encouraging; marked visual improvements have been demonstrated, the perceptual benefits transfer to new visual tasks and appear to be relatively enduring. The essential ingredients of perceptual training protocols are being incorporated into video game formats, facilitating home-based interventions. Summary: Many studies support perceptual training as a tool for improving vision in amblyopes beyond the critical period. Should this novel form of treatment stand up to the scrutiny of a randomised controlled trial, clinicians may need to re-evaluate their therapeutic approach to adults with amblyopia.

Temporal Instabilities in Amblyopic Perception: A Quantitative Approach

“…This interpretation may confirm the results of Astle, Webb, and McGraw (2011a) who found that training on tasks using crowded and broadband stimuli (in spatial frequency and orientation) results in greater amounts of learning compared to tasks using uncrowded, narrowband stimuli (like simple Gabor patches).…”

Efficiency of electronically monitored amblyopia treatment between 5 and 16years of age: New insight into declining susceptibility of the visual system

“…Correlations between them may elucidate mechanisms of plasticity of various structures in the visual system. Our data may gain additional importance in the context of various attempts to influence amblyopia with alternative approaches such as perceptual learning (Astle, Webb, & McGraw, 2011;Levi & Li, 2009;Polat, Ma-Naim, & Spierer, 2009), playing video games (Li et al, 2011), various types of binocular training (Hess, Mansouri, & Thompson, 2011;Knox et al, 2012), as well as acupuncture (Zhao et al, 2010), pharmacological enhancement (Campos & Fresina, 2006;Maya Vetencourt et al, 2008), and transcranial magnetic (rTMS, Clavagnier, Thompson, & Hess, 2013;Thompson et al, 2008) or current stimulation (Spiegel et al, 2013a(Spiegel et al, , 2013b, many of which are hardly applicable in young children. Our acuity gain, dose-response and efficiency data may serve as reference for the age dependent effort (e.g.…”

A dichoptic custom-made action video game as a treatment for adult amblyopia

“…The initial studies employing PL did so under monocular viewing with the participants being required to perform fine discriminations of basic stimulus features over thousands of trials with their amblyopic eye only (Astle, Webb, & McGraw, 2011; Chung, Li, & Levi, 2006, 2008; see recent reviews in Levi & Li, 2009; Levi & Polat, 1996; Levi, Polat, & Hu, 1997; Li, Klein, & Levi, 2008; Li & Levi, 2004; Li et al, 2005; Polat, 2008; Polat et al, 2004; Zhang et al, 2013, 2014; Zhou et al, 2006). Improvements, although sometimes taskand stimulus-specific (see Zhang et al, 2014), often show some transfer to visual acuity (Levi & Li, 2009; Levi & Polat, 1996; Levi, Polat, & Hu, 1997; Li & Levi, 2004) and even stereovision (Zhang et al, 2014).…”