Computed tomography of the optic canals.

Radiographic delineation of the optic canals was first performed by Winckler [1] in 1901 and then by Rhese [2], who outlined the canal in the oblique position. Further refinements were made by Goalwin [3, 4], who examined 1,000 optic canals, and later by Pfeiffer [5], whose x-ray techniques are now commonly used in projecting the optic foramen in the inferolateral quadrant of the orbit. The simultaneous demonstration of both optic canals in their axial plane by complex motion tomography [6, 7] further improved the detection of subtle abnormalities. However, a drawback of this technique is that it requires a skilled technician and a cooperative patient. The hyperextended head position required to obtain the satisfactory angle is often difficult for adult patients. Computed tomography (CT) has now enabled routine detailed visualization of the optic canals without subjecting the patient to any discomfort.