Combining fixation and lateral masking training enhances perceptual learning effects in patients with macular degeneration

tRNS boosts visual perceptual learning in participants with bilateral macular degeneration

Perceptual learning (PL) has shown promise in enhancing residual visual functions in patients with age-related macular degeneration (MD), however it requires prolonged training and evidence of generalization to untrained visual functions is limited. Recent studies suggest that combining transcranial random noise stimulation (tRNS) with perceptual learning produces faster and larger visual improvements in participants with normal vision. Thus, this approach might hold the key to improve PL effects in MD. To test this, we trained two groups of MD participants on a contrast detection task with (n = 5) or without (n = 7) concomitant occipital tRNS. The training consisted of a lateral masking paradigm in which the participant had to detect a central low contrast Gabor target. Transfer tasks, including contrast sensitivity, near and far visual acuity, and visual crowding, were measured at pre-, mid and post-tests. Combining tRNS and perceptual learning led to greater improvements in the trained task, evidenced by a larger increment in contrast sensitivity and reduced inhibition at the shortest target to flankers' distance. The overall amount of transfer was similar between the two groups. These results suggest that coupling tRNS and perceptual learning has promising potential applications as a clinical rehabilitation strategy to improve vision in MD patients.

Efficacy of binocular vision training and Fresnel press-on prism on children with esotropia and amblyopia

PURPOSE

In the process of clinical diagnosis and treatment of amblyopia, we have found that the treatment time of this disease was significantly different among different patients. The purpose of this study was to compare the efficacy of binocular vision training (BVT) and Fresnel press-on prism (FPP) on children with esotropia combined with amblyopia.

METHODS

From May 2015 to December 2018, a total of 101 children aged 3-9 years with esotropia and amblyopia who were in our hospital were enrolled in this randomized clinical trial. They were randomly divided into combined group (48 cases) and prism group (53 cases): the children in the prism group received FPP treatment, and those in the combined group received the combined treatment of BVT and FPP. The visual acuity, the binocular function and the strabismic therapeutic effects were compared between two groups.

RESULTS

After treatment, the visual acuity in both groups was both significantly improved compared with that before treatment (P = 0.0079). The binocular-monocular function, including synoptophore visual function and the Titmus stereopsis, in both groups was significantly improved compared with those before treatment (P < 0.05), and it was more significant in the combined group compared with the prism group (P < 0.05). The cure rate of strabismus was 87.50% (42/48) and 30.19% (16/53) in the combined group and the prism group, respectively, and there was significant difference between groups (P = 0.0036). The cure time was shortened with the lower of the degree of esotropia.

CONCLUSION

BVT combined with FPP can effectively promote the recovery of binocular vision in children with esotropia combined with amblyopia, and some children can achieve complete cure of strabismus.

Empowerment-Based Physical Activity Intervention for People with Advanced Dry Age-Related Macular Degeneration: Mixed-Methods Protocol

Age-related macular degeneration (AMD) is the most common cause of incurable visual impairment and impacts daily life. These impacts include loss of social activities, decreased functional independence, and reduced physical activity. This protocol aims to describe a prospective, mixed-methodology for studying a population with AMD before, during, and after an empowerment-based physical activity intervention (EPI). A study framework was also developed for EPI. The intervention will include 20 older individuals (age 65+ years) with AMD recruited in Sweden. The intervention period is six months and comprises adapted physical activity and social activities in a group twice a week and individual health coaching on three occasions. The quantitative pre-test and three follow-ups include physical functional tests, an accelerometer that monitors physical activity continuously for one week, and questionnaires. Individual and focus-group interviews and ethnographic observations will explore the experience of living with AMD and what it means to participate in the EPI for individuals with AMD. The chosen methodology offers a structured way for researchers to explore the experiences and factors that may provide insights into the potential of creative supervised, adapted physical activity in groups, health coaching, and socialising that are significant to enable well-being among older individuals with AMD.

Oculomotor changes following learned use of an eccentric retinal locus

People with bilateral central vision loss sometimes develop a new point of oculomotor reference called a preferred retinal locus (PRL) that is used for fixating and planning saccadic eye movements. How individuals develop and learn to effectively use a PRL is still debated; in particular, the time course of learning to plan saccades using a PRL and learning to stabilize peripheral fixation at the desired location. Here we address knowledge limitations through research describing how eye movements change as a person learns to adopt an eccentric retinal locus. Using a gaze-contingent, eye tracking-guided paradigm to simulate central vision loss, 40 participants developed a PRL by engaging in an oculomotor and visual recognition task. After 12 training sessions, significant improvements were observed in six eye movement metrics addressing different aspects involved in learning to use a PRL: first saccade landing dispersion, saccadic re-referencing, saccadic precision, saccadic latency, percentage of useful trials, and fixation stability. Importantly, our analyses allowed separate examination of the stability of target fixation separately from the dispersion and precision of the landing location of saccades. These measures explained 50% of the across-subject variance in accuracy. Fixation stability and saccadic precision showed a strong, positive correlation. Although there was no statistically significant difference in rate of learning, individuals did tend to learn saccadic precision faster than fixation stability. Saccadic precision was also more associated with accuracy than fixation stability for the behavioral task. This suggests effective intervention strategies in low vision should address both fixation stability and saccadic precision.

Current directions in visual perceptual learning

The visual expertise of adult humans is jointly determined by evolution, visual development, and visual perceptual learning. Perceptual learning refers to performance improvements in perceptual tasks after practice or training in the task. It occurs in almost all visual tasks, ranging from simple feature detection to complex scene analysis. In this Review, we focus on key behavioral aspects of visual perceptual learning. We begin by describing visual perceptual learning tasks and manipulations that influence the magnitude of learning, and then discuss specificity of learning. Next, we present theories and computational models of learning and specificity. We then review applications of visual perceptual learning in visual rehabilitation. Finally, we summarize the general principles of visual perceptual learning, discuss the tension between plasticity and stability, and conclude with new research directions.

Vision recovery with perceptual learning and non-invasive brain stimulation: Experimental set-ups and recent results, a review of the literature

BACKGROUND

Vision is the sense which we rely on the most to interact with the environment and its integrity is fundamental for the quality of our life. However, around the globe, more than 1 billion people are affected by debilitating vision deficits. Therefore, finding a way to treat (or mitigate) them successfully is necessary.

OBJECTIVE

This narrative review aims to examine options for innovative treatment of visual disorders (retinitis pigmentosa, macular degeneration, optic neuropathy, refractory disorders, hemianopia, amblyopia), especially with Perceptual Learning (PL) and Electrical Stimulation (ES).

METHODS

ES and PL can enhance visual abilities in clinical populations, inducing plastic changes. We describe the experimental set-ups and discuss the results of studies using ES or PL or their combination in order to suggest, based on literature, which treatment is the best option for each clinical condition.

RESULTS

Positive results were obtained using ES and PL to enhance visual functions. For example, repetitive transorbital Alternating Current Stimulation (rtACS) appeared as the most effective treatment for pre-chiasmatic disorders such as optic neuropathy. A combination of transcranial Direct Current Stimulation (tDCS) and visual training seems helpful for people with hemianopia, while transcranial Random Noise Stimulation (tRNS) makes visual training more efficient in people with amblyopia and mild myopia.

CONCLUSIONS

This narrative review highlights the effect of different ES montages and PL in the treatment of visual disorders. Furthermore, new options for treatment are suggested. It is noteworthy to mention that, in some cases, unclear results emerged and others need to be more deeply investigated.

Perspectives on the Combined Use of Electric Brain Stimulation and Perceptual Learning in Vision

A growing body of literature offers exciting perspectives on the use of brain stimulation to boost training-related perceptual improvements in humans. Recent studies suggest that combining visual perceptual learning (VPL) training with concomitant transcranial electric stimulation (tES) leads to learning rate and generalization effects larger than each technique used individually. Both VPL and tES have been used to induce neural plasticity in brain regions involved in visual perception, leading to long-lasting visual function improvements. Despite being more than a century old, only recently have these techniques been combined in the same paradigm to further improve visual performance in humans. Nonetheless, promising evidence in healthy participants and in clinical population suggests that the best could still be yet to come for the combined use of VPL and tES. In the first part of this perspective piece, we briefly discuss the history, the characteristics, the results and the possible mechanisms behind each technique and their combined effect. In the second part, we discuss relevant aspects concerning the use of these techniques and propose a perspective concerning the combined use of electric brain stimulation and perceptual learning in the visual system, closing with some open questions on the topic.

Training peripheral vision to read: Using stimulus exposure and identity priming

Reading in the periphery can be improved with perceptual learning. A conventional training paradigm involves repeated practice on a character-based task (e.g., recognizing random letters/words). While the training is effective, the hours of strenuous effort required from the trainees makes it difficult to implement the training in low-vision patients. Here, we developed a training paradigm utilizing stimulus exposure and identity priming to minimize training effort and improve training accessibility while maintaining the active engagement of observers through a stimulus visibility task. Twenty-one normally sighted young adults were randomly assigned to three groups: a control group, a with-repetition training group, and a without-repetition training group. All observers received a pre-test and a post-test scheduled 1 week apart. Each test consisted of measurements of reading speed, visual-span profile, the spatial extent of crowding, and isolated-letter profiles at 10° eccentricity in the lower visual field. Training consists of five daily sessions (a total of 7,150 trials) of viewing trigram stimuli (strings of three letters) with identity priming (prior knowledge of target letter identity). The with-repetition group was given the option to replay each stimulus (averaged 0.4 times). In comparison to the control group, both training groups showed significant improvements in all four performance measures. Stimulus replay did not yield a measurable benefit on learning. Learning transferred to various untrained tasks and conditions, such as the reading task and untrained letter size. Reduction in crowding was the main basis of the training-related improvement in reading. We also found that the learning can be partially retained for a minimum of 3 months and that complete retention is attainable with additional monthly training. Our findings suggest that conventional training task that requires recognizing random letters or words is dispensable for improving peripheral reading. Utilizing stimulus exposure and identity priming accompanied by a stimulus visibility task, our novel training procedure offers effective intervention, simple implementation, capability for remote and self-administration, and an easy translation into low-vision reading rehabilitation.

Perspective on Vision Science-Informed Interventions for Central Vision Loss

Pathologies affecting central vision, and macular degeneration (MD) in particular, represent a growing health concern worldwide, and the leading cause of blindness in the Western World. To cope with the loss of central vision, MD patients often develop compensatory strategies, such as the adoption of a Preferred Retinal Locus (PRL), which they use as a substitute fovea. However, visual acuity and fixation stability in the visual periphery are poorer, leaving many MD patients struggling with tasks such as reading and recognizing faces. Current non-invasive rehabilitative interventions are usually of two types: oculomotor, aiming at training eye movements or teaching patients to use or develop a PRL, or perceptual, with the goal of improving visual abilities in the PRL. These training protocols are usually tested over a series of outcome assessments mainly measuring low-level visual abilities (visual acuity, contrast sensitivity) and reading. However, extant approaches lead to mixed success, and in general have exhibited large individual differences. Recent breakthroughs in vision science have shown that loss of central vision affects not only low-level visual abilities and oculomotor mechanisms, but also higher-level attentional and cognitive processes. We suggest that effective interventions for rehabilitation after central vision loss should then not only integrate low-level vision and oculomotor training, but also take into account higher level attentional and cognitive mechanisms.