The assessment of traumatic optic neuropathy in a neurologically impaired patient is difficult, and the size of the optic nerve has been suggested as a potential adjunct in differential diagnosis. This controlled retrospective study was designed to evaluate the size of the optic nerve involved in traumatic optic neuropathy when compared to the optic nerve in the noninjured eye. Maxillofacial computerized tomographs of 22 patients were examined; intraorbital optic nerve diameter was measured on injured and noninjured sides, with the examiner unaware of the side of injury. No statistically significant difference in size was found between the traumatized optic nerves and those that remained intact. The authors have concluded that the size of the optic nerve is not a reliable predicator of the presence or absence of traumatic optic neuropathy when measured with computerized tomograph scans.