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W. E. Adams, H. Haggerty, J. Dickinson, A. Coulthard; Graves Ophthalmopathy - Predictors of Diplopia. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1981.
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© ARVO (1962-2015); The Authors (2016-present)
Patients with Graves Ophthalmopathy (GO) frequently experience diplopia due to restrictive myopathy. Some investigators have suggested that the MRI measurements of extraocular muscle volume can be used to predict ocular motility and diplopia. We compared muscle volumes and uniocular fields of fixation (UFOF) to the field of binocular single vision (BSV).
24 patients with GO were evaluated by plotting a field of BSV on the Goldmann perimeter and scored from 0 (constant diplopia) to 100 (no diplopia). UFOF were plotted for each eye along 6 muscle axes. Muscle volumes were measured from 3-D MRI images. UFOF measurements and muscle volumes were compared between the 12 patients with significant diplopia (BSV score <80) and the 12 without significant diplopia (BSV≥80).
The patients with diplopia had lower UFOF scores for 7 of 8 muscles compared to those without diplopia (Right Medial Rectus 37.0 deg vs 48.2, R Lateral Rectus 32.1 vs 42.8, R Inferior Rectus 19.9 vs 32.5, R Superior Rectus 44.7 vs 55.5, Left Medial Rectus 37.9 vs 47.7, L Lateral Rectus 34.3 vs 43.3, L Inferior Rectus 25.1 vs 33.9, p < 0.01 for all comparisons). Only the UFOF of the LSR was borderline significantly different (47.6 deg vs 54.7, p=0.06). In contrast, individual muscle volumes (mm3 ) although numerically larger in patients with severe diplopia, were statistically similar (RMR 938.8 vs 836.8, RLR 809.4 vs 705.8, RIR 1050.3 vs 948.9, RSR 1185.8 vs 874.2, LMR 1066.6 vs 895.8, LLR 788.3 vs 672.6, LIR 1078.0 vs 846.5, LSR 1182.3 vs 874.3, all comparisons p>0.05). Total muscle volumes and total orbital volumes were also similar (8075.5 +/- 2632.7 vs 6671.2 +/- 1904.9, p= 0.1 and 41298.3 +/- 9140.9 vs 37405.3 +/- 8776.0, p=0.3 respectively).
Diplopia in GO is strongly associated with reductions of individual muscle ductions, but this association is not paralleled by significant differences in muscle volumes. MRI cannot be used to predict motility and diplopia, and restriction should be assessed by clinical methods such as UFOF and BSV.
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