The traditional view has been that the brain is hardwired in early childhood, therefore one could not expect significant recovery of function in an adult’s injured brain. Recent findings show that in fact the brain has remarkable plasticity that is retained throughout an adult’s lifetime, and hence specific therapies for both motor and visual impairments have been developed leading to significant recovery. The process that the brain goes through to regain lost functions, for example lost vision, is called neuroplasticity. When a brain is damaged so is the network of neurons that process vision. Some networks in the brain however are duplicated and the systematic stimulation of the damaged area with light stimuli at a specific location enables the activation and usage of alternative routes to process the visual information. The brain in essence develops a bypass mechanism. Repetitive stimulation has proven effective not only in vision but also in the recovery of other functions such as movements of lower limbs after stroke.
VRT is designed to strengthen the visual information processing of residual neuronal structures that have survived following acute lesions of the nervous system resulting from trauma, stroke, inflammation, or elective surgery for removal of brain tumours or the like. By repeated activation through the course of the therapy, VRT is designed to improve the neuronal efficacy of such residual cells, i.e., patients use the program to train and improve their impaired visual functions, and thus regain useful vision in the area of the visual field deficit.
While the patient focuses on a central fixation point on a computer screen, light stimuli are repetitively presented in the transition zones between the intact and damaged visual field. These areas have the highest potential to improve. Light stimuli parameters (i.e., size and brightness) are determined to address each patient’s unique needs. Patients are made to respond to the repetitive stimulation, such that visual processing in the areas of impaired vision is repetitively activated over the course of the therapy leading to recovery of visual function.
VRT has multiple phases, including diagnostics, stimulation and evaluation of visual performance. In the diagnostic phase, it is essential to establish the precise limits and boundaries of the lost vision. This is done initially using High-Resolution Perimetry (HRP) when small white light dots are briefly presented on a grid (central ±20 x ±15 degrees) in random locations. Detection of a dot requires patient response. The task is repeated 3 times and the results are averaged. A map of visual sensitivity is then produced based on the frequency of detection at each point. In addition, the reaction time of the patient is recorded.
Following the initial diagnostic phase, the patient undergoes repeated stimulation of a the areas of the impaired visual field that show residual vision and are therefore most likely to improve. Intense, frequently repeated light stimulation has proven to strengthen and restore visual functions in the targeted areas of the visual field.
While patients are performing the stimulation therapy at home, performance quality parameters are controlled: a central fixation point changes intermittently colour or shape and the patient is required to respond after each change. A lack of response after a fixation change is a measure of fixation accuracy whereas a button press in the absence of a target presentation is considered as a false alarm response.
The final stage of VRT involves determination of visual fields, using High-Resolution Perimetry (HRP), when again detection of very small white dots at multiple locations is measured repeatedly, and the responses after three consecutive runs are averaged to obtain a map of visual sensitivity. Visual fields are then compared pre and post VRT to assess the improvements gained.