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X. Shan, H. S. Ying, J. Tian, D. L. Guyton, R. Tamargo, M. Walker, D. S. Zee; Effect of Corrective Strabismus Surgery After Unilateral IV Nerve Palsy in Monkey: I. Vertical Alignment and Head Tilt. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4869.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the effect of corrective strabismus surgery on vertical misalignment following induced IV nerve palsy (SOP) in rhesus monkeys.
The IV nerve was sectioned intracranially in 2 rhesus monkeys (M1 and M2). More than 4 months after lesion, the ipsilateral IO muscle was denervated and extirpated for both M1 and M2. After another 4 months, M2 received contralateral IR recession (2.0 mm). Eye movements were recorded pre and post-correction during straight ahead or eccentric fixation (±20°, horizontal and/or vertical) with the head upright or tilted (±30º).
With the initial SOP, monkeys developed a vertical deviation (VD) that increased with down gaze and adduction. Post-lesion, the VD stabilized at 5.0° in straight and 11.3° in adduction/down gaze for M1, and 11.9° and 14.7° for M2. Following IO surgery, VD was neutralized in straight-ahead gaze for M1 (0.32°). For M2, VD improved modestly in straight ahead gaze (5.3°) but improved more in up gaze (1.4°) and also showed more comitancy across horizontal positions. After IR recession, VD was neutralized in straight-ahead gaze for M2 (0.64°). The gradient of VD from 30° head tilt towards the normal side to 30° head tilt to the paretic side post-lesion was 3.0° for M1 and 8.1° for M2. Following IO surgery, this gradient decreased to 1.6° for M1 and 4.8° for M2. Following IR recession in M2, this gradient slightly increased to 5.7°.
Rhesus monkeys with induced IV nerve palsy show changes after corrective strabismus surgery in vertical alignment similar to those shown by humans treated for acquired IV nerve palsy.
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