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A. Pradeep, R. J. McLean, F. A. Proudlock, I. Gottlob; Vertical Smooth Pursuit in Congenital Idiopathic Nystagmus. Invest. Ophthalmol. Vis. Sci. 2007;48(13):877.
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It has been suggested that Congenital Idiopathic Nystagmus (CIN) may be caused by instability of the normal pursuit subsystem. Most CIN occurs along the horizontal axis with the majority of investigations analysing the axis of oscillation.We compared pursuit function in volunteers with horizontal CIN to age matched controls along the unaffected vertical axis.
Horizontal and vertical eye movements were recorded at 250 Hz in 15 patients with CIN and 24 age matched controls when following a smooth pursuit target with a linear velocity of 20°/s and amplitude of ±20°. The pursuit gain was measured in along the vertical axis.
Pursuit gains were 0.74 (SD 0.20) and 0.70 (SD 0.14) in nystagmus volunteers and 0.72 (SD 0.22) and 0.65 (SD 0.15) in controls for upward and downward moving stimuli, respectively. Consequently, there is no significant difference in vertical smooth pursuit gain between idiopathic nystagmus subjects and controls. We also found that volunteers could pursue the vertical targets during horizontal foveating and non-foveating periods.
We found the pursuit gain for nystagmus volunteers was normal along the vertical axis. These findings may indicate that oculomotor deficits may be limited only to the axis of oscillation in CIN and other axes have otherwise normal oculomotor function.
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