Cortical Blindness

Damage to visual cortex on one side of the brain frequently produces a profound and permanent blindness in contralesional space (hemianopia), a debilitating condition that causes enormous suffering for patients and their families.

The BRIGHT (Behavioral Rehabilitation Through Image-Guided Home-based Training) study aims to evaluate the effectiveness of image-guided, home-based perceptual training at improving visual performance in individuals with visual field loss. Using a prospective, crossover design, BRIGHT combines visual behavioral testing, neuroimaging, and a home-based intervention. It aims to 1) identify neural pathways that support training-induced visual plasticity; and 2) compare the efficacy of different types of visual training delivered in a home-based setting.

This is a randomized, pilot interventional study in participants with visual field deficit (VFD) caused by cortical lesion. Damage to the primary visual cortex (V1) causes a contra-lesional, homonymous loss of conscious vision termed hemianopsia, the loss of one half of the visual field. The goal of this project is to elaborate and refine a rehabilitation protocol for VFD participants. It is hypothesized that visual restoration training using moving stimuli coupled with noninvasive current stimulation on the visual cortex will promote and speed up recovery of visual abilities within the blind field in VFD participants. Moreover, it is expected that visual recovery positively correlates with reduction of the blind field, as measured with traditional visual perimetry: the Humphrey visual field test or an eye-tracker based visual perimetry implemented in a virtual reality (VR) headset. Finally, although results will vary among participants depending on the extent and severity of the cortical lesion, it is expected that a bigger increase in neural response to moving stimuli in the blind visual field in cortical motion area, for those participants who will show the largest behavioral improvement after training. The overarching goals for the study are as follows: Group 1a will test the basic effects of transcranial random noise stimulation (tRNS) coupled with visual training in stroke cohorts, including (i) both chronic/subacute ischemic and chronic hemorrhagic VFD stroke participants, and (ii) longitudinal testing up to 6 months post-treatment. Group 1b will test the effects of transcranial tRNS coupled with visual training on a Virtual Reality (VR) device in stroke cohorts, including both chronic/subacute ischemic and chronic hemorrhagic VFD stroke participants. Group 2 will examine the effects of tRNS alone, without visual training, also including chronic and subacute VFD stroke participants and longitudinal testing.

This project will collect brain imaging data to quantify the effects of early visual cortex damage and visual training interventions on the structure and function of the residual visual system. Our goal is to improve understanding of the consequences of permanent visual cortex damage in humans, and to understand how visual training impacts the function of the residual visual system to restore perception.

The VIBRANT (Vision Improvement through Behavioral Rehabilitation And Neuroplasticity Training) study is a prospective, double-blind, crossover design (within-subject) in participants with homonymous hemianopia-a type of visual field loss resulting from damage to the post-chiasmatic visual pathways. It aims to investigate whether transcranial random noise stimulation (tRNS) combined with perceptual learning-based training has potential for improving visual impairments.

This project is intended to collect data using standard clinical tests and psychophysics to quantify the effect of visual cortical damage on the structure of the residual visual system, visual perception, spatial awareness, and brain function. The investigators will also assess the effect of intensive visual retraining on the residual visual system, processing of visual information and the use of such information in real-world situations following damage. This research is intended to improve our understanding of the consequences of permanent visual system damage in humans, of methods that can be used to reverse visual loss, and of brain mechanisms by which visual recovery is achieved.