Association of visual field, cup-disc ratio, and magnetic resonance imaging of optic chiasm.

Abstract

To assess the association of visual field, vertical cup-disc (VC/D) ratio, and vertical height of optic chiasm. Case series. Outpatient eye clinic. Eighteen patients with low, normal, or elevated intraocular pressure, with or without visual field defects. Measurement of visual field, VC/D ratio, and vertical height of optic chiasm. Association between VC/D ratio and visual field defects compared with association between vertical height of optic chiasm and visual field defects. Visual field defects were graded as 0, 1 to 10, and 11 to 20 (from least to most severe). Group mean VC/D ratios were 0.47 (0), 0.55 (1-10), and 0.69 (11-20) for right eyes and 0.48 (0), 0.57 (1-10), and 0.75 (11-20) for left eyes. The significance level for trend was P = .02 for right eyes and P = .006 for left eyes. Group mean chiasm heights were 3.5 (0), 2.9 (1-10), and 2.2 (11-20) mm for right eyes and 3.5 (0), 2.8 (1-10), and 2.2 (11-20) mm for left eyes. The significance level for trend was P < .001 for right eyes and P = .002 for left eyes. To assess the simultaneous effects of VC/D ratio and chiasm height on the visual field defects groups, we used ordinal logistic regression models. Models with both variables implied that chiasm height was a stronger predictor of visual field defects group than VC/D ratio (for right eyes, P = .04 [VC/D ratio], P = .001 [chiasm height]; for left eyes, P = .11 [VC/D ratio], P = .005 [chiasm height]). When chiasm and VC/D ratio were analyzed in the same model, chiasm height was a stronger predictor of visual field defects. In advanced visual field defects, the optic chiasm is atrophic.