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X. Shan, I. Hamazaki, J. Tian, H. Ying, R. Tamargo, D. S. Zee; Evolution of Vertical Alignment in Monkey Following Acute Unilateral Iv Nerve (sop) Palsy: Effects of Paretic vs. Intact Eye Viewing. Invest. Ophthalmol. Vis. Sci. 2010;51(13):2998.
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We previously reported changes in vertical alignment with intracranial section of the IV nerve in two rhesus monkeys (IOVS 2007). Each animal wore a patch in front of the paretic eye (PE) for 6-9 days beginning immediately post-lesion. With habitual normal eye (NE) viewing the vertical deviation (VD) decreased gradually over several days, after habitual binocular viewing was allowed the VD gradually increased. The comitancy of the VD changed pari passu with the VD amplitude. Here we investigated changes in vertical alignment and comitancy in a monkey (M6) following SOP with habitual paretic eye (PE) viewing.
NE was immediately patched post lesion and kept patched for 4 weeks. Eye movements were recorded pre and post-lesion during straight ahead and eccentric fixation ±20° with the PE viewing. To assess comitancy, a gradient (Δ VD/ Δ eye position) was calculated (larger gradient = less comitant deviation) along the horizontal (HG) or the vertical (VG) meridian.
Post-lesion, the paretic eye was extorted and the monkey had a VD (PE hyper) greater in adduction(ADD) and in down gaze. The VD was 5.1° in straight ahead, 10.9° in adduction/down gaze; In the first week post-lesion, with the NE patched the VD decreased to 2.6° in straight ahead, and 9.7° in adduction down gaze. However, even with the NE still patched, after 7 days post-lesion the VD began to increase gradually and, by 4 weeks post-lesion it reached a maximum of 9.0° in straight ahead and 15.3° in adduction/down gaze. Post-lesion, with the initial decrease in VD, the HG along horizontal midline changed from 0.16 to 0.08 in ADD and 0.14 to 0.12 in abduction (ABD). VG along vertical midline remained 0.14 in upgaze but increased from 0.17 to 0.20 in downgaze. By the end of 4 weeks with the increase in VD, VG gradually increased to 0.21 in up gaze and ~0.25 in down gaze, while HG changed little.
Our data shows that the initial decrease and the late increase in vertical misalignment after SOP occurred during habitual monocular PE viewing just as with habitual NE viewing as reported previously. With the late increase in ocular misalignment in this monkey, the VD gets more incomitant along the vertical meridian.
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