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Frank A Proudlock, Vijay Patel, Rebecca J McLean, Irene Gottlob; Head oscillations in infantile nystagmus during tasks of varying visual demand. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2582.
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© ARVO (1962-2015); The Authors (2016-present)
Involuntary head oscillations are often associated with infantile nystagmus (IN) although the nature and cause of the oscillations is unclear. Head oscillations in IN increase during tasks with higher visual demand, however it is unclear if this simply reflects normal patterns of head tremor or whether the oscillations provide any benefit in reducing nystagmus. We compare head and eye oscillations in IN volunteers with age-matched controls during tasks of varying visual demand.
Horizontal and vertical head and eye oscillations were measured at 1000Hz using a head and pupil tracker in 17 IN participants (10 with albinism, 6 idiopathic, 1 achromat) and 14 controls when performing two tasks of high visual demand (visual acuity and reading tasks where letters become progressively smaller) and three tasks of low visual demand (eyes closed, fixation task, fixation with mental maths task). The amount of head oscillations were quantified by summing the area under the curve of power spectral density functions between 1-10Hz. Nystagmus characteristics were evaluated during the visual acuity and fixation tasks and were compared when the head was fixed using a bite bar.
A larger degree of head oscillations were observed in both the IN and control group when performing the two tasks of higher visual demand compared to the fixation and eyes closed task. The differences were highly significant in the IN group (p<0.005 for all comparison) but only some comparisons reached significance in controls as larger head oscillations were observed in the IN group overall. Nystagmus intensity and foveation characteristics were not significantly different between tasks although the nystagmus frequency was slower during the fixation tasks compared to the visual acuity tasks (p<0.05). Nystagmus oscillations were even slower during the mental maths task. Fixing the head did not significantly change the nystagmus.
Similar patterns of head oscillations were observed in the IN group and controls in relation to visual demand suggesting that changes in head oscillations observed in IN with visual task are not specific to IN but are more apparent in IN because of the larger head oscillations overall. The head oscillations did not appear to influence the overall intensity or foveation characteristics of the nystagmus. This suggests that head oscillations have a similar role in IN and normal controls.
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