Abstract
Purpose: :
To define clinical background factors such as thyroid function, systemic and ocular history, and Magnetic Resonance Imaging (MRI) features in patients with dysthyroid optic neuropathy (DON).
Methods: :
The study involved 42 consecutive DON patients (male: 17, female: 25) of which 72 eyes were examined. All patients underwent visual field and MRI examination. Mean age was 58 years old.
Results: :
Patients with thyroid dysfunction included Graves' disease (40 patients), and Hashimoto disease (2 patients). Of those with Graves' disease 2 (5%) were pregnant females and 4 (10%) had undergone radioiodine treatment. Thyrotropin receptor antibodies (TRAb) and thyroid stimulating antibodies (TSAb) were found to be present in 31 of 37 and 38 of 38 patients, respectively. In past history, 6 patients had diabetes and 4 had hepatitis. Twenty-seven patients (64%) were smokers or ex-smokers. In ophthalmic examination the proptosis ranged from 12 to 24 mm (average 18.1 mm). Best corrected visual acuity was less than 20/200 in 15 eyes and 20/25 or better in 19 eyes. All eyes had visual fields abnormalities and reduced critical flicker fusion frequency (CFF). Optic disc appearance was normal in 36 eyes (50%) with DON. Orbital imaging using MRI showed apical muscle crowding in all eyes. Forty five eyes had enlargement of 4 rectus muscles, 21 had enlargement of 3 rectus muscles, 5 had enlargement of 2 rectus muscles, and one only involved the superior rectus. In T2 enhanced MRI, 25 of 67 eyes had superior ophthalmic vein enhanced.
Conclusions: :
Patients with DON did not show severe proptosis or abnormal optic disc features. TSAb should be tested in equivocal DO patients as this was found to be present in all patients. Radiological evidence of optic nerve compression is the most useful clinical features in DON, as all eyes showed involvement of at least one rectus muscle.
Keywords: orbit • extraocular muscles: structure • optic nerve