Neurologically related visual field defects (VFDs) can occur as a consequence of stroke, traumatic brain injury, or complications of brain surgery. VFDs can occur in one eye (ocular injury) or both eyes (brain injury), and range from partial loss of vision field to complete blindness. So much of human perception, learning, cognition, and daily activities are mediated through vision that visual loss of any sort can be devastating to patients’ lives. In one study of stroke patients, for example, the probability of reaching relative independence (as measured on a standard disability scale, the Barthel Index) was diminished by 20% when a visual field defect is present, and the chances of walking >150 feet was reduced from 35% to 3%1.

Until recently, the only clinically available treatments to assist patients with visual field cuts were prism lenses and oculomotor (eye movement) training. These approaches are “compensatory” in nature, in that the training relies on the acquisition of strategies to compensate for the impairment, rather than attempt to treat the impairment itself.  Many current rehabilitation strategies work on the compensatory principle -- for example learning to use a wheelchair when gait is impaired, or being trained to use the non-dominant hand to write if the dominant hand is weak. Although these compensatory strategies have an important role in getting the patient back to performing some activities of daily living, they leave untreated the impairment itself.  There is growing evidence in the neuroscience community, however, that actual restoration of function through treatment at the level of impairment is possible, and can be accomplished through targeted behavioral, pharmacological, and brain stimulation techniques. These newer, targeted therapies are thought to work through “neuroplasticity,” which is the ability of the nervous system to modify its structural and functional organization in order to respond to changes in one’s environment or recover from injury.  By working to reverse the impairment, a better ultimate outcome may be expected. It is in the category of impairment-targeted treatment that visual restoration therapy (VRT) is thought to work. Some initial data have been published from our lab regarding the brain reorganization that occurs early in the course of VRT treatment.2

Visual restoration therapy is a home-based, computerized visual stimulation treatment that was developed in the late1990s by a neuroscientist in Germany, and introduced clinically in the US in 2003.  It is now being offered across an expanding number of academic institutions and clinics in this country.  Columbia University Medical Center was among the first to offer the therapy in the US.  Because of my lab’s ongoing clinical research on mechanisms of stroke recovery, we were interested in participating in the VRT program from a clinical as well as scientific perspective. We have treated 67 patients to date, some of whom have participated in our research investigations.

Tracking the results of our patients form a clinical perspective, we find that approximately 50% of patients have a significant expansion of their visual fields, ranging from 3% to 20% (average 8.2%) absolute increase in detection of stimuli in visual areas that were previously blind. Furthermore, approximately 61% report subjective improvement, including faster reading speed, better mobility (e.g. bumping into things less), a return to previous hobbies, and overall improved visual function. Our results with regard to the visual field improvement are slightly lower than previously reported results3-5 which were derived from NovaVision’s automated visual field testing that patients perform at home at the end of each monthly module.  The main reason for the discrepancy we have come to learn is that some patients acquire a compensatory strategy of briefly shifting their eyes toward the blind field in order to bring stimuli into their seeing fields. These rapid out-and-back eye movements (visual saccades) are often performed without conscious awareness on the part of the patient, and may be a consequence of the VRT training procedure itself.  When these eye movements are controlled for using a specialized eye camera there still appears to be true visual field expansion, which is the primary goal of the therapy. It may turn out that a combination of visual field expansion and subconsciously trained saccades account for the improvements in visual function that patients experience.

In addition to visual field expansion, the VRT stimulation therapy appears to confer additional benefits in other realms of cognitive restoration, in particular sustained attention. One young man we treated, a 19 year old who had suffered head trauma from a motor vehicle accident 3 years prior, gained attentional skills such that he went from a score of 8 of 9 measures on a test for attentional deficit disorder prior to starting VRT, to a score of 1 of 9 by the end of the therapy. Thus, improved global and directed attention, a common accompanying deficit in head injury, may be an important secondary benefit to VRT.

I would conclude that VRT has significant merit in the treatment of visual field defects following brain injury, and may contribute to improved functioning, both at the level of the visual impairment, as well as improvement of disability and quality of life.

References.

1.         Reding MJ, Potes E. Rehabilitation outcome following initial unilateral hemispheric stroke. Life table analysis approach. Stroke. 1988;19:1354-1358

2.         Marshall RS, Ferrera JJ, Barnes A et al. Brain Activity Associated With Stimulation Therapy of the Visual Borderzone in Hemianopic Stroke Patients. Neurorehabil Neural Repair. 2008;22:136-144

3.         Kasten E, Bunzenthal U, Sabel BA. Visual field recovery after vision restoration therapy (VRT) is independent of eye movements: an eye tracker study. Behav Brain Res. 2006;175:18-26

4.         Kasten E, Wust S, Behrens-Baumann W, Sabel BA. Computer-based training for the treatment of partial blindness. Nat Med. 1998;4:1083-1087

5.         Poggel DA, Kasten E, Sabel BA. Attentional cueing improves vision restoration therapy in patients with visual field defects. Neurology. 2004;63:2069-2076