Visual rehabilitation using microperimetric acoustic biofeedback training in individuals with central scotoma

Patients with central scotoma have poor fixation stability and poor visual acuity. Acoustic biofeedback training can be an effective way to train such patients to eccentrically fixate. This study analyses the mean retinal sensitivity, saccadic velocity, and fixation stability after acoustic biofeedback training and shows correlation with age and scotoma size.

Patients with irreversible central scotoma in both the eyes secondary to macular diseases were selected. After undergoing comprehensive low vision assessment, 19 patients who were willing were recruited for the acoustic biofeedback training to the better eye in 10 sessions, using the MP-1 Microperimeter. Mean retinal sensitivity, saccadic velocity, fixation stability before and after the acoustic biofeedback were recorded.

There were 17 men and two women. Ages ranged from 19-94 years (mean 54.63 ± 24.66). The scotoma size ranged from four to 20 degrees. Ten patients had age-related macular degeneration, four had Stargardt disease, three had traumatic macular scar, two had scarred myopic choroidal neovascular membrane, and one had myopic macular degeneration. The vision improved from 1.06 ± 0.36 to 0.86 ± 0.33 logMAR (p < 0.0001). The mean retinal sensitivity improved from 2.1 ± 2.9 dB to 2.7 ± 3.1 dB (p = 0.01), with negative correlation with age (p = 0.01) and scotoma size (p = 0.02). Fixation stability improved with reduction in the bivariate contour ellipse area (p = 0.01). It showed negative correlation with age (p = 0.02) and scotoma size (p = 0.10). The saccadic velocity reduced from 0.34°/second to 0.26°/second but was not significant (p > 0.99). The majority (58 per cent) had their preferred retinal locus superior to the fovea. There was good agreement between bivariate contour ellipse area and MP-1 Microperimeter inbuilt fixation parameters. The effect was maintained at six months with slight reduction in fixation stability.

Acoustic biofeedback can improve fixation behaviour, visual acuity and retinal sensitivity in patients with central scotoma. The results are better with younger age and smaller scotoma size.