How does thyroid eye disease typically affect ocular motility?

How does thyroid eye disease typically affect ocular motility?

• A. Restrictive strabismus due to enlarged extraocular muscles, commonly IR and MR; results in incomitancy and diplopia with limited ductions particularly in downgaze.
• B. Paretic involvement of the lateral rectus only.
• C. Superior oblique myopathy with cyclodeviation.
• D. Isolated pupil anomalies with preserved motility.

Answer: (A)

Thyroid eye disease causes the extraocular muscles to enlarge and become fibrotic, producing a mechanical restriction of movement rather than a nerve palsy. The inferior rectus and medial rectus are most commonly involved, so the eyes have difficulty moving freely in certain directions, leading to an eye misalignment that changes with gaze (incomitancy) and diplopia. The restriction is especially evident when trying to look downward because the inferior rectus is typically the affected muscle, limiting downgaze. Other options describe nerve palsy or isolated pupil problems, which don’t fit the typical restrictive pattern seen in thyroid eye disease.

Thyroid eye disease causes the extraocular muscles to enlarge and become fibrotic, producing a mechanical restriction of movement rather than a nerve palsy. The inferior rectus and medial rectus are most commonly involved, so the eyes have difficulty moving freely in certain directions, leading to an eye misalignment that changes with gaze (incomitancy) and diplopia. The restriction is especially evident when trying to look downward because the inferior rectus is typically the affected muscle, limiting downgaze. Other options describe nerve palsy or isolated pupil problems, which don’t fit the typical restrictive pattern seen in thyroid eye disease.