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Dongsheng Yang, Amy Nau, Richard W. Hertle; Effect Of Tongue Stimulation On Nystagmus: Evidence Of Afferent Influence On Eye Movements. Invest. Ophthalmol. Vis. Sci. 2011;52(14):3020.
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To report dramatic effects of tactile tongue stimulation on nystagmus eye movements in patients with acquired blindness.
Six adult subjects (3 subjects with light perception or worse vision and 3 normal subjects) were included in this study. Causes of blindness included: traumatic explosion, anterior ischemic optic neuropathy, and central retinal artery occlusions. Duration of the blindness was 15 years, 3 years and 1.5 years respectively. A video eye tracking system (Eyelink 1000, desktop system) was used to record eye movements at a 500 Hz sampling frequency. Subjects were instructed to look straight ahead and their eye movements were recorded for 120 seconds. The eye movement recording (EMR) was repeated four times in about 20 minutes. Two of EMRs were performed without tongue stimulation and two with tongue stimulation in randomized order. Normal subjects completed the same EMRs with careful eye movement calibration. Tongue stimulus was applied to the surface of the tongue by a tongue pad matrix that produced electrical tactile stimulus in a sine wave pattern. The frequency of the nystagmus with and without tongue stimulation was analyzed.
All blind subjects showed continuous nystagmus with slow and quick phases in both horizontal and vertical planes in their primary eye positions. The recorded nystagmus waveforms were mainly jerk with linear velocity slow phases. No nystagmus eye movements were recorded from normal subjects. The frequency of nystagmus in the blind subjects was dramatically reduced by 47%, 40% and 11% respectively when the tongue stimulus was applied.
We hypothesize that the effects of tongue stimulation on nystagmus is an evidence of afferent influence on eye movements.
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