Trochlea of superior oblique muscle
Muscles · Latin: Trochlea musculi obliqui superioris
The superior oblique muscle loops through a pulley-like structure (the trochlea of superior oblique) and inserts into the sclera on the posterotemporal surface of the eyeball.
It is the pulley system that gives superior oblique its actions, causing depression of the eyeball despite being inserted on the superior surface.
Definition from Wikipedia, CC BY-SA 4.0.