Thyroid eye disease
Thyroid eye disease (also known as thyroid associated orbitopathy). This is an unusual condition which occurs as a result of thyroid disease, usually Graves. Patients often present with diplopia and proptosis, which are caused by enlargement of the extraocular muscles due to infiltration by inflammatory cells. Typically, the inferior and medial rectus muscles are the first to be involved. In this example, if you compare the two sides you will notice that the inferior and medial recti are severely thickened on the right (arrows), and that the right globe protrudes further anteriorly from the orbit than the left. When advanced, this condition can result in optic nerve compression and blindness. In some cases, thyroid eye disease can predate the actual thyroid abnormality.