Related Papers
Transcranial direct current stimulation enhances recovery of stereopsis in adults with amblyopia
Winston Byblow, Daniel P. Spiegel
Amblyopia is a neurodevelopmental disorder of vision caused by abnormal visual experience during early childhood that is often considered to be untreatable in adulthood. Recently, it has been shown that a novel dichoptic videogame-based treatment for amblyopia can improve visual function in adult patients, at least in part, by reducing inhibition of inputs from the amblyopic eye to the visual cortex. Non-invasive anodal transcranial direct current stimulation has been shown to reduce the activity of inhibitory cortical interneurons when applied to the primary motor or visual cortex. In this double-blind, sham-controlled cross-over study we tested the hypothesis that anodal transcranial direct current stimulation of the visual cortex would enhance the therapeutic effects of dichoptic videogame-based treatment. A hom*ogeneous group of 16 young adults (mean age 22.1 ± 1.1 years) with amblyopia were studied to compare the effect of dichoptic treatment alone and dichoptic treatment combined with visual cortex direct current stimulation on measures of binocular (stereopsis) and monocular (visual acuity) visual function. The combined treatment led to greater improvements in stereoacuity than dichoptic treatment alone, indicating that direct current stimulation of the visual cortex boosts the efficacy of dichoptic videogame-based treatment. This intervention warrants further evaluation as a novel therapeutic approach for adults with amblyopia.
Anodal transcranial direct current stimulation temporarily improves contrast sensitivity and normalises visual cortex activation in individuals with amblyopia
Daniel P. Spiegel, Winston Byblow
Background Amblyopia is a neurodevelopmental disorder of vision that is associated with abnormal patterns of neural inhibition within the visual cortex. This disorder is often considered to be untreatable in adulthood due to insufficient visual cortex plasticity. There is increasing evidence that interventions which target inhibitory interactions within the visual cortex, including certain types of non-invasive brain stimulation, can improve visual function in adults with amblyopia. Objective We tested the hypothesis that anodal transcranial direct current stimulation (a-tDCS) would improve visual function in adults with amblyopia by enhancing the neural response to inputs from the amblyopic eye. Methods Thirteen adults with amblyopia participated and contrast sensitivity in the amblyopic and fellow fixing eye was assessed before, during and after a-tDCS or cathodal tDCS (c-tDCS). Five participants also completed an fMRI study designed to investigate the effect of a-tDCS on the BOLD response within the visual cortex to inputs from the amblyopic vs. the fellow fixing eye. Results A subgroup of 8/13 participants showed a transient improvement in amblyopic eye contrast sensitivity for at least 30 minutes after a-tDCS. fMRI measurements 3 indicated that the characteristic cortical response asymmetry in amblyopes which favours the fellow eye was reduced by a-tDCS. Conclusions These preliminary results suggest that a-tDCS deserves further investigation as a potential tool to enhance amblyopia treatment outcomes in adults.""""
Scientific Reports
The effect of transcranial direct current stimulation on contrast sensitivity and visual evoked potential amplitude in adults with amblyopia
2016 •
Daniel P. Spiegel
Amblyopia is a neurodevelopmental disorder of vision that occurs when the visual cortex receives decorrelated inputs from the two eyes during an early critical period of development. Amblyopic eyes are subject to suppression from the fellow eye, generate weaker visual evoked potentials (VEPs) than fellow eyes and have multiple visual deficits including impairments in visual acuity and contrast sensitivity. Primate models and human psychophysics indicate that stronger suppression is associated with greater deficits in amblyopic eye contrast sensitivity and visual acuity. We tested whether transcranial direct current stimulation (tDCS) of the visual cortex would modulate VEP amplitude and contrast sensitivity in adults with amblyopia. tDCS can transiently alter cortical excitability and may influence suppressive neural interactions. Twenty-one patients with amblyopia and twenty-seven controls completed separate sessions of anodal (a-), cathodal (c-) and sham (s-) visual cortex tDCS. A...
Current Biology
Brain Plasticity in the Adult: Modulation of Function in Amblyopia with rTMS
2008 •
Behzad Mansouri
Annals of the New York Academy of Sciences
The Pathophysiology of Amblyopia: Electrophysiological Studies
1980 •
Dennis Levi
Vision Research
Is the motion system relatively spared in amblyopia? Evidence from cortical evoked responses
1996 •
Colin Blakemore
Scientific Reports
Reduced evoked activity and cortical oscillations are correlated with anisometric amblyopia and impairment of visual acuity
2021 •
Satu Palva
Amblyopia is a developmental disorder associated with abnormal visual experience during early childhood commonly arising from strabismus and/or anisometropia and leading to dysfunctions in visual cortex and to various visual deficits. The different forms of neuronal activity that are attenuated in amblyopia have been only partially characterized. In electrophysiological recordings of healthy human brain, the presentation of visual stimuli is associated with event-related activity and oscillatory responses. It has remained poorly understood whether these forms of activity are reduced in amblyopia and whether possible dysfunctions would arise from lower- or higher-order visual areas. We recorded neuronal activity with magnetoencephalography (MEG) from anisometropic amblyopic patients and control participants during two visual tasks presented separately for each eye and estimated neuronal activity from source-reconstructed MEG data. We investigated whether event-related and oscillatory...
IEEE Access
Cortical Activity at Baseline and During Light Stimulation in Patients With Strabismus and Amblyopia
Torres-pacheco Irineo
Journal of nuclear medicine : official publication, Society of Nuclear Medicine
Brain SPECT evaluation of the visual cortex in amblyopia
1995 •
Tanju Erdil
In amblyopia, the number of visual cortical neurons are reduced and abnormal or absent sensitivity to retinal light stimulation of the amblyopic eye is demonstrated. Ten amblyopic patients were studied to evaluate the response of the visual cortex to visual stimulation. All patients with unilateral amblyopia received 500-550 MBq 99mTc-HMPAO during visual stimulation. Strobe light flashing was used as the stimulus for five patients and a checkerboard pattern reversal was used in the other five patients, closing one eye. For both groups a 2-Hz frequency was used. One week later, the same procedure was repeated with the opposite eye closed. SPECT images were reconstructed with prefiltering techniques and sliced along the orbitomeatal line. For all patients, the amblyopic eye demonstrated less radioactivity in the visual cortex than in the normal eye. The mean cerebral-to-cerebellar ratios were 0.95 +/- 0.05 and 1.09 +/- 0.07 for amblyopic and normal eyes, respectively (p < 0.0001). ...
Combined Therapy of Bilateral Transcranial Direct Current Stimulation and Ocular Occlusion Improves Visual Function in Adults with Amblyopia, a Randomized Pilot Study
2021 •
Ivan Rosales
Amblyopia is the interocular visual acuity difference of two lines or more with best correction in both eyes. Ocular occlusion therapy depends on neuroplasticity, and thus is effective in children but not in adult with later diagnoses. Transcranial Direct Current Stimulation (tDCS) is suggested to increase neuroplasticity. To determine if combined therapy of bilateral tDCS and ocular occlusion improves visual function in adults with amblyopia, we conducted a double blind randomized, controlled pilot trial in volunteers with amblyopia (ClinicalTrials.gov Identifier: NCT05016830). While applying ocular occlusion and performing a reading task, participants received sham bilateral tDCS or bilateral tDCS. Visual function and visual evoked potential were evaluated immediately after. 12 volunteers with amblyopia were randomized, 2 were excluded after misdiagnosis confirmation. A significant increase in visual acuity was observed after stimulation in the bilateral group (n = 5) versus the s...
