Which extraocular muscle enlargement is most likely to cause optic nerve compression in Thyroid Eye Disease?

Which extraocular muscle enlargement is most likely to cause optic nerve compression in Thyroid Eye Disease?

• A. Inferior rectus
• B. Medial rectus
• C. Lateral rectus
• D. Superior rectus

Answer: (B)

In thyroid eye disease, inflammatory swelling causes the extraocular muscles to enlarge, and the space at the orbital apex is very tight. The muscle closest to the optic nerve at that point is the medial rectus, so when it enlarges it most readily crowds the posterior orbit and compresses the optic nerve. This proximity explains why optic nerve compression is most often due to medial rectus enlargement. The other muscles can enlarge as well, but their position farther from the nerve makes direct compression at the apex less likely.

In thyroid eye disease, inflammatory swelling causes the extraocular muscles to enlarge, and the space at the orbital apex is very tight. The muscle closest to the optic nerve at that point is the medial rectus, so when it enlarges it most readily crowds the posterior orbit and compresses the optic nerve. This proximity explains why optic nerve compression is most often due to medial rectus enlargement. The other muscles can enlarge as well, but their position farther from the nerve makes direct compression at the apex less likely.