The effects of Graves' eye disease on levator muscle function.

The levator function and exophthalmometer reading were measured on each side of 81 patients with Graves' eye disease (GED) and 111 normal subjects. There was a significant positive correlation between the levator function and exophthalmometer reading for both GED patients and normal subjects. This indicates that the forward position of the eye chronically stretches the levator muscle by the addition of sarcomeres which increases the range of movement of the lid. The range of movement may be decreased in patients with Graves' eye disease, from inflammation, such as is seen with other extraocular muscles. This effect is most likely to be marked in the patient with compressive optic neuropathy.