Medial rectus volume only independent predictor of dysthyroid optic neuropathy

This retrospective case series found medial rectus volume to be the only significant independent predictor of compressive dysthyroid optic neuropathy (DON). Orbital geometry was not predictive.

The authors reviewed the images of 198 orbits from 99 patients suffering from thyroid-related orbitopathy.

Multivariate modeling found only medial rectus volume to be a significant independent predictor of optic neuropathy. Significant volumetric univariate predictors of DON included medial rectus volume (P = 0.005), lateral rectus volume (P = 0.011), superior muscle group volume (P = 0.04) and total rectus muscle volume (P = 0.015). Assessment of orbital geometry, including bowing of the medial wall, orbital apex angle, globe diameter and orbital volume, were not found to be predictive of DON.

The authors note that the area under the ROC curves were similar between medial rectus volume and medial rectus maximal diameter. This suggests that the simple and quick 2-D correlates of volume and medial rectus maximal diameter as measured on axial scans are equivalent in their ability to predict DON.