Rehabilitation of damage to the visual brain

Abstract

Homonymous visual field loss is a common consequence of stroke and traumatic brain injury. It is associated with an adverse functional prognosis and has implications on day-to-day activities such as driving, reading, and safe navigation. Early recovery is expected in around half of cases, and may be associated with a return in V1 activity. In stable disease, recovery is unlikely beyond three and certainly six months. Rehabilitative approaches generally target three main areas, encompassing a range of techniques with variable success: visual aids aim to expand or relocate the affected visual field; eye movement training builds upon compensatory strategies to improve explorative saccades; visual field restitution aims to improve visual processing within the damaged field itself. All these approaches seem to offer modest improvements with repeated practice, with none clearly superior to the rest. However, a number of areas are demonstrating particular promise currently, including simple web-based training initiatives, and work on neuroimaging and learning. The research interest in this area is encouraging, and it is to be hoped that future trials can better untangle and control for the number of complicated confounds, so that we will be in a much better position to evaluate and select the most appropriate therapy for patients.

Quantifying the pattern of optic tract degeneration in human hemianopia

“…Over the past few years, attempts have been made to develop therapies that may improve visual function in patients with hemianopia 5 6. The most common interventions fall into three main groups: optical therapies, eye movement training and restorative therapies including Vision Restoration Therapy7 and Neuro-eye Therapy 8.…”

Changes in perilesional V1 underlie training-induced recovery in cortically-blind patients

“…The prevalence of blindnessinducing post-chiasmal lesions of the visual system in the general population is remarkably high (Pollock et al, 2011), and its impact on everyday life deeply debilitating (Papageorgiou et al, 2007). Yet, there is a lack of validated clinical therapies that can help restore, rather than compensate for, deficits in CB patients (Ajina and Kennard, 2012;Chokron et al, 2008;Melnick et al, 2016b;Perez and Chokron, 2014;Pollock et al, 2011;Urbanski et al, 2014). In stark contrast with well-established physical therapies prescribed following motor cortex strokes, the ability of restitution therapies to restore vision in CB patients remains controversial.…”

“…One proposed recovery mechanism is that training stimulates and improves visual processing in extrageniculostriate pathways mediating blindsight (Ajina and Kennard, 2012;Chokron et al, 2008;Das and Huxlin, 2010;Perez and Chokron, 2014;Smirnakis, 2016). Both human and non-human primates with V1 lesions exhibit visually-guided perceptual abilities within their blind field, despite lacking awareness (Ajina and Bridge, 2016;Leopold, 2012;Weiskrantz et al, 1974).…”

“…Both human and non-human primates with V1 lesions exhibit visually-guided perceptual abilities within their blind field, despite lacking awareness (Ajina and Bridge, 2016;Leopold, 2012;Weiskrantz et al, 1974). Because blindsight is elicited by large stimuli with high-temporal and low-spatial frequency content, it is thought to rely mainly on direct geniculo-hMT+ and superior colliculus-pulvinar-extrastriate projections (Ajina and Bridge, 2016;Ajina and Kennard, 2012;Ajina et al, 2015;Bridge et al, 2008;Leopold, 2012;Schmid et al, 2010;Weiskrantz et al, 1974). Accordingly, some rehabilitation approaches have targeted blindsight to help CB patients recruit these unconscious processes, with some evidence of increased visual performance and awareness post-training (Chokron et al, 2008;Melnick et al, 2016b;Perez and Chokron, 2014;Sahraie et al, 2010;Sahraie et al, 2006).…”

Not prism prescription, but prism adaptation rehabilitates spatial neglect; a reply to Bansal, Han and Ciuffreda

“…The final result of looking through a full field prism is the same as without a prism and no gain of visual field is obtained. Other uses of a prism in order to ameliorate hemianopia have been devised and tested, such as sector prism and vision multiplexing, together with other rehabilitative approaches [5].…”