Abstract • Quantitative assessment of computed tomographic (CT) scans was performed on 98 orbits of 49 patients with Graves' ophthalmopathy. Extraocular muscle volume and orbital fat volume were determined, according to whether optic neuropathy was absent, had developed during follow-up, or was present at the time of scanning. No differences in muscle volume were found between the group already having optic neuropathy and the group in which optic neuropathy developed during follow-up. Both optic neuropathy groups, however, had significant increases in extraocular muscle volume compared with the group without optic neuropathy. The absolute amount of orbital fat was the same for all groups, but the relative amount of orbital fat tended to decrease as total orbital volume increased with development or presence of optic neuropathy. This study establishes a quantitative relationship between optic neuropathy and extraocular muscle enlargement in Graves' ophthalmopathy. Orbital fat, however, does not play an important role in the disease. References 1. Kroll AJ, Kuwabara T: Dysthyroid ocular myopathy: Anatomy, histology, and electron microscopy . Arch Ophthalmol 1966;76:244-257.Crossref 2. Rundle FF, Pochin EE: The orbital tissues in thyrotoxicosis: A quantitative analysis relating to exophthalmos . Clin Sci 1944;5:51-74. 3. Riley FC: Orbital pathology in Graves' disease . Mayo Clin Proc 1972;47:975-979. 4. Trokel SL, Jakobiec FA: Correlation of CT scanning and pathologic features of ophthalmic Graves' disease . Ophthalmology 1981;88:553-564.Crossref 5. Coleman DJ, Jack RL, Franzen LA, et al: High resolution B-scan ultrasonography of the orbit: Eye changes of Graves' disease . Arch Ophthalmol 1972;88:465-471.Crossref 6. Shammas HJF, Minckler DS, Ogden C: Ultrasound in early thyroid orbitopathy . Arch Ophthalmol 1980;98:277-279.Crossref 7. Kennerdell JS, Rosenbaum AE, El-Hoshy MH: Apical optic nerve compression of dysthyroid optic neuropathy on computed tomography . Arch Ophthalmol 1981;99:807-809.Crossref 8. Trokel SL, Hilal SK: Submillimeter resolution CT scanning of orbital diseases . Ophthalmology 1980;87:412-417.Crossref 9. Feldon SE, Weiner JM: Clinical significance of extraocular muscle volumes in Graves' ophthalmopathy: A quantitative computed tomography study . Arch Ophthalmol 1982;100:1266-1269.Crossref 10. Penn RD, Belanger MG, Yasnoff WA: Ventricular volume in man computed from CAT scans . Ann Neurol 1978;3:216-223.Crossref 11. Steiner L, Bergvall U, Zwetnow N: Quantitative estimation of intracerebral and intraventricular hematoma by computer tomography . Acta Radiol 1975;346( (suppl) ):143-154. 12. Pentlow KS, Rottenberg DA, Deck MDF: Partial volume summation: A simple approach to ventricular volume determination from CT . Neuroradiology 1978;16:130-132.Crossref 13. Feldon SE, Muramatsu S, Weiner JM: Clinical classification of Graves' ophthalmopathy: Identification of risk factors for optic neuropathy . Arch Ophthalmol 1984;102:1469-1472.Crossref 14. Smelser GK: Experimental studies on exophthalmos . Am J Ophthalmol 1962;54:929-951.
Archives of Ophthalmology – American Medical Association
Published: Feb 1, 1985