Ultrasonographic Measurements of Extraocular Muscle Thickness in Normal Eyes and Eyes with Orbital Disorders Causing Extraocular Muscle Thickening

Abstract

The thickness of the extraocular muscles was determined by ultrasonography using St. Marianna’s high-powered ultrasonic diagnostic equipment (ZD-252). The mean thickness of the extraocular muscles was 3.5 mm for the medial rectus muscle. 3.4 mm for the lateral rectus muscle, 3.3 mm for the superior rectus muscle, and 3.4 mm for the inferior rectus muscle in 240 eyes of Japanese normal adults. The thickness ranged from 4.1 to 4.3 mm in 34 eyes with dysthyroid ophthalmopathy, showing significantly thicker muscles than that in normal persons. As a result of ultrasonography of the extraocular muscles in patients with orbital myositis and inflammatory pseudotumor, the thickness of the extraocular muscles of the affected eye was significantly greater than that of the healthy eye. Ultrasonography of the extraocular muscle was considered to be useful for early diagnosis and observation of the course of dysthyroid ophthalmopathy, as well as certain other orbital disorders, and for evaluating therapeutic effects.