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Reduction of congenital nystagmus amplitude with auditory biofeedback
1Dr Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, and the Department of Biomedical Engineering, Indian Institute of Technology, New Delhi, India. anudeep@ndf.usnl.net.in
Purpose:
Treatment options for congenital nystagmus without null position are limited. The purpose of this study was to evaluate the role of auditory biofeedback in controlling congenital nystagmus.
Methods:
Ten patients with congenital nystagmus without null position underwent 6 sessions (twice a week for 3 weeks) of auditory biofeedback. Each half-hour session had simultaneous electronystagmographic recording done during the session.
Results:
The patients could reduce the nystagmus during the treatment sessions. Mean amplitude (degrees) of nystagmus was reduced from 6. 28 +/- 4.94 to 3.05 +/- 2.48 (P =.028) and mean intensity (amplitude x frequency) was reduced from 33.37 +/- 22.84 to 13.35 +/- 7.99 (P =. 0174), but the mean frequency change was not significant, from 5.8 +/- 1.05 to 4.98 +/- 1.35 (P =.148). The mean amplitude and mean intensity decreased by 51% and 60%, respectively. After completion of the session, although a subjective improvement was reported, the patient's binocular visual acuity on Snellen's charts and contrast sensitivity did not show any significant change. Also no sustained benefit was noted because the electronystagmographic recordings reverted to baseline after the auditory stimulus for biofeedback was discontinued.
Conclusion:
Simultaneous electronystagmographic recording shows significant reduction of nystagmus amplitude and intensity because of auditory biofeedback only during the treatment session. The beneficial effect does not persist after the auditory stimulus is discontinued. No objective effect on visual acuity and contrast sensitivity was noted after the therapy.