The intermuscular septum of the inferior oblique muscle: revised concepts.

The classical anatomical descriptions of the inferior oblique muscle give little or no account of its intermuscular fascial septum. Operative and cadaver dissections show that a definite and constant fascial septum exists between the sheaths of the inferior oblique and the lateral and inferior recti. The clinical significance of this fascia is realised when it is pulled laterally, as its inner surface provides a guide to the inferior oblique sheath; also, when a muscle hook is placed under the lateral rectus muscle it may snag the septum and kink the inferior oblique and cause its overaction. The fascia forms a sling for the inferior oblique sheath and helps to maintain its line of action. For these reasons the intermuscular septum of the inferior oblique should be included in anatomical accounts of the ocular fascia and should be remembered during operations on the inferior oblique or lateral rectus muscles.