The microanatomy of the superior orbital fissure (SOF) was studied in 96 sides 
of cadaver specimens. The SOF is a narrow bony cleft that lies at the apex of 
the orbit between the greater and lesser wings of the sphenoid. Through this 
fissure, many important structures enter the orbit from the middle cranial fossa 
including the third, fourth, sixth cranial nerves, and the ophthalmic branch of 
the fifth nerve. In addition, the superior opthalmamic vein exits the orbit to 
drain into the cavernous sinus via the SOF. The fissure can be divided into 
three anatomical regions by the annulus of Zinn (common annular tendon): the 
lateral, central, and inferior regions. The lateral wall of the SOF can also be 
divided between the upper and lower segments, and the angle between them was 
measured to be 144.27 degrees +/- 20.03 degrees . Defining these regions is 
useful in describing the course and placement of the nerves and vasculature in 
the SOF. Managing lesions at the orbital apex requires an extensive knowledge of 
the cranial base and the intracranial and extracranial relationships of the 
anatomical structures coursing through the SOF. The goal of this study was to 
describe the microanatomy of the SOF region in detail and to provide a reference 
for surgical procedures involving the orbital apex.