Double insertion of superior oblique muscle of the eye: a rare variation.

Superior oblique muscle of the eye is involved in depression, abduction and intorsion of the eyeball. Knowledge of its variations is useful for understanding and repairing strabismus cases and other visual problems. We report a rare unilateral variation of right superior oblique muscle. The superior oblique muscle had a normal origin. However, it had two insertions. Its tendon passed through the fibrous trochlea and was inserted to the sclera in a usual manner. In addition, it had an additional insertion to the roof of the orbit through an aponeurosis. We also observed the encroachment of the roof of the orbit by the frontal and ethmoidal air sinuses. The knowledge of these variations could be important to ophthalmologists.