Table of Contents
ISRN Ophthalmology
Volume 2014, Article ID 435276, 6 pages
http://dx.doi.org/10.1155/2014/435276
Clinical Study

Orbital Volumetry in Graves' Orbitopathy: Muscle and Fat Involvement in relation to Dysthyroid Optic Neuropathy

1Department of Ophthalmology, Glostrup Hospital, University of Copenhagen, Glostrup, Denmark
2Eye Clinic 2061, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, Copenhagen, Denmark
3Department of Endocrinology, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, Copenhagen, Denmark
4Department of Radiology, Rigshospitalet, University of Copenhagen, Blegdamsvej 9, Copenhagen, Denmark

Received 22 December 2013; Accepted 17 February 2014; Published 2 April 2014

Academic Editors: L. Pierro and L. Racette

Copyright © 2014 Moug Al-Bakri et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose. We wanted to investigate the relative significance of fat and muscle enlargement in the development of dysthyroid optic neuropathy (DON) in Graves’ orbitopathy (GO). Methods. Preoperative coronal CT scans of 13 patients with and without DON who subsequently underwent orbital decompression were retrospectively analyzed. Thirteen patients imaged for unilateral orbital fractures served as controls. Results. The retrobulbar muscle volume was 2.1 ± 0.5 cm3 (mean ± SD) in controls, 4.3 ± 1.5 cm3 in GO without DON, and 4.7 ± 1.7 cm3 in GO with DON. The retrobulbar fat volume was 5.4 ± 1.6 cm3 in controls, 8.7 ± 8.0 cm3 in GO without DON, and 9.4 ± 3.1 cm3 in GO with DON. The muscle and fat volumes were higher in patients with GO than in controls (), but the volumes in orbits with and without DON were not significantly different. The volume of the optic nerve were similar in the 3 groups. The number of apical, coronal 2 mm thick slices with no fat was 2.9 ± 0.9 in normal orbits, it was 4.1 ± 1.0 in GO orbits without DON and 5.3 ± 0.8 in GO orbits with DON (). Conclusion. Apical muscle enlargement may be more important than orbital fat enlargement in the development of DON. However, the fact that apical crowding and muscle enlargement also occur in orbits without DON suggests that other factors also play a role in the development of DON.