Vision restoration therapy (VRT) after brain damage: retrospective analysis of visual fields in 300 patients and eye movement recordings

Objective: Restoration of visual field defects have long been considered impossible. However, visual plasticity can be induced by a computer-based training program, „Vision Restoration Therapy (VRT)“. We now wished to determine the role of eye movements in this process and analyzed retrospectively the effects of VRT in a 300 patient sample. Background: VRT stimulates areas of residual vision („relative defects“) during daily training for a 6 months period which results in visual field enlargements as shown perimetrically. We now replicated our earlier findings with a larger patient population and in a separate patient sample we checked the role of eye movements in this process. Design/Methods: Visual field charts generated by computer-based high resolution perimetry (HRP) of 300 patients were obtained from the NovaVision Clinic in Magdeburg. HRP charts were compared before and after VRT and stimulus detection and reaction times were quantified. This was validated by standard near-threshold perimetry in 69 patients. Because eye movements might possibly contribute to apparent visual improvements, we also measured eye movements in a separate group of 20 patients using eye-tracker recordings before and after VRT. Results: After VRT there the ability of patients to detect visual stimuli increased from 56.57±0.85% at baseline to 66.30±0.91% at final testing (t=-16.13, p<0.001). In addition, the reaction time improved significantly from 463.6 ms±5.08ms to 446.2 ms±5.23 ms, while fixation performance remained stable. Visual field enlargements were confirmed in standard near-threshold perimetry. Eye tracker recordings demonstrated that eye movements did not systematically changed after VRT, as hemianopic patients looked equally as often to each side (no preference toward the hemianopic field) and the average distance of the eye position from fixation point remained unchanged. Conclusion: Restoration of vision following VRT was thus confirmed in a large patient sample. Eye tracker recordings provide evidence that visual field recovery is not caused by eye movements but is rather the consequence of true restoration of some visual functions. VRT is therefore effective in inducing neuroplasticity of the visual system, though more work needs to be done to determine the precise neurobiological/cognitive mechanisms involved in visual field recovery.