Thyroid ophthalmopathy presenting as superior oblique paresis.

Six patients with thyroid ophthalmopathy presented with what appeared to be a unilateral superior oblique paresis by the three-step test, which was eventually followed by more typical findings of thyroid disease. This early motility defect in thyroid ophthalmopathy may be caused by a restrictive process due to involvement of the inferior rectus muscle. Clues to the proper diagnosis included an increase in vertical deviation in upgaze, elevation of intraocular tension in upgaze, and the lack of excyclodeviation. These features should be assessed in patients with isolated superior oblique paresis.