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Giovanni Sato, Gianfrancesco M. Villani, Roberta Rizzo, Carlo Camerucci, Ronald A. Schuchard; Analysis Of Mp-1 Audio-biofeedback Impact On Fixation in Low Vision. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4368.
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To study the impact of a low vision rehabilitation strategy based on Nidek MP-1 auditory biofeedback (BFB).
Retrospective study of 39 eyes/26 consecutive patients referred for low vision rehabilitation. Patients received 8 monocular training sessions of BFB, each of 10 minutes duration, 7-14 days apart. Microperimetry (MP-1, Nidek Tech., Padova, Italy) was performed at the beginning and at the end of the sequence, as well as ETDRS visual acuity (VA) and Pelli-Robson Contrast Sensitivity (CS) at 1 meter. BFB employs a sound to train the patient to keep a specific gaze position, which is marked on the digital retinal image by the operator and displayed as a target to the patient. As long as the patient's gaze matches the selected position, a continuous sound is emitted. When the eye drifts away, the sound becomes progressively more discontinuous.
Age median (range) was 70 (98-56). Pre-BFB logMAR VA was 1 (2-0.5), CS 0.60 (1.2-0). Post-BFB logMAR VA was 1 (2-0.3), CS 0.75 (1.35-0.30). Dense central scotomas and eccentric fixation locations were detected in 35 eyes/24 patients, and relative scotomas with central fixations in 4 eyes/2 patients. Mean sensitivity was 7.60 dB (15.70-0.10) pre-BFB, and 8 db (18-0.10) post-BFB. Pre-BFB fixation stability was 24% (60-2%) within 2°, and 67% (96-19%) within 4°; post-BFB, it was 25% (80-4%) within 2°, and 64% (98-17%) within 4°. BCEA (area of fixation stability) analysis showed pre-BFB values for 68.2% BCEA to be 3.6 (24.4-0.85), and 4.46 (25.5-0.71) post-BFB. After BFB, no significant difference was found for any of the above-mentioned parameters in the sample as a whole. Nevertheless, grouping cases by change in pre- vs post-BFB BCEA (group A: decrease in BCEA, n= 21; group B: increase in BCEA, n= 18) showed a significant difference in terms of BCEA itself, and in the related fixation stability (p<0.05).
Although no significant difference in VA, CS, mean sensitivity, fixation stability at 2° and 4°, and BCEA was found after BFB in the sample as a whole, still there was an improvement in 21 eyes (53,8%) in terms of BCEA and fixation stability. Grouping analysis demonstrated that, while other tested outcome measures were not affected, some cases did respond significantly to BFB improving their fixation stability. However, this study does not suggest any pre-selection criteria of patient characteristics to identify responders before training is done.
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