Quantitative computed tomographic predictors of compressive optic neuropathy in patients with thyroid orbitopathy: a volumetric analysis.
OBJECTIVE
To evaluate the relationship between orbital bony geometry and the volume of the intraorbital structures in predicting compressive dysthyroid optic neuropathy (DON).


METHODS
Retrospective, consecutive case series.


METHODS
Images of 198 orbits from 99 patients suffering from thyroid-related orbitopathy were reviewed.


METHODS
Clinical examination and computed tomography of the orbits, including volumetric analysis, were performed on all patients.


METHODS
Clinical and radiologic predictors of DON.


RESULTS
Significant volumetric univariate predictors of compressive optic neuropathy 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). Inferior rectus muscle volume, orbital volume, bony orbital apex angle, globe diameter, and bony medial wall contour were not associated with optic neuropathy. Multivariate modeling found medial rectus volume the only independently significant predictor. Univariate modeling of simple rectus diameter measurements found medial rectus axial diameter (P = 0.003) and total recti diameter (P = 0.016) predictive of optic neuropathy. Lateral rectus, superior rectus, and inferior rectus diameters were not predictive. Multivariate modeling found only medial rectus diameter to be a significant independent predictor of optic neuropathy. The area under the receiver operating characteristic curve was not different between the volumetric and rectus diameter curves.


CONCLUSIONS
Medial rectus size was found to be the most important quantifiable predictor of compressive optic neuropathy in patients with optic neuropathy. In this study, simple maximum medial rectus diameter, as measured on axial scans, was equally predictive of compressive optic neuropathy as the more involved volumetric calculation. 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.
Department of Ophthalmology, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada. ezekiel_weis@post.harvard.edu
Ezekiel
E
Weis
Manraj K S
MK
Heran
Ashu
A
Jhamb
Andy K
AK
Chan
Jack P
JP
Chiu
Michael C
MC
Hurley
Jack
J
Rootman
D005188:False Negative Reactions; D005260:Female; D049970:Graves Ophthalmopathy / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009801:Oculomotor Muscles / Q000000981:diagnostic imaging; D009901:Optic Nerve Diseases / Q000000981:diagnostic imaging*; D009915:Orbit / Q000000981:diagnostic imaging; D009916:Orbital Diseases / Q000000981:diagnostic imaging*; D009929:Organ Size; D011237:Predictive Value of Tests; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed