Visual field expansion after visual restoration therapy

Abstract

Objective: To determine whether visual field expansion occurs with visual restoration therapy (VRT), using fundus-controlled microperimetry to assess visual fields. Design: This longitudinal cohort analysis assesses patients’ visual fields before and after visual restoration therapy using microperimetry and standard high-resolution perimetry. Subjects: Seven patients with stroke-induced homonymous field cuts were studied. Intervention: Visual restoration therapy is a computerized, home-based treatment aimed at reducing the size of the visual field defect of stroke patients with hemianopia through repetitive stimulation of the visual borderzone adjacent to the blind field. During twice-daily therapy for three months patients maintain central fixation while responding to eccentrically placed stimuli in the visual borderzone. The programme is adjusted monthly to changes in the patient’s visual field. Controversy exists as to whether expansion of visual fields measured at home with high-resolution perimetry is due to inadvertent eye movements and therefore would overrepresent the treatment’s effect. Main measures: Microperimentry uses an infrared camera to track retinal vessels so that any shift or movement between the reference image and the real-time fundus image corrects the stimulus position, thus delivering stimuli to known retinal locations, and allowing accurate assessment of visual fields independent of eye movements. Results: There was an average improvement in stimulus detection rate by microperimetry of 12.5% (range —1.4% to 38.9%, P =0.033). Six of 7 patients had ≥ 3% improvement in stimulus detection by home-based perimetry. Conclusion: Our results demonstrate modest but real expansion in visual fields following visual restoration therapy which is not due to eye movements.