title: Ultrasonography in distinguishing optic neuritis from nonarteritic anterior ischemic optic neuropathy.
abstract: OBJECTIVE
  Optic neuritis (ON) and nonarteritic anterior ischemic optic neuropathy (NAION) have some overlapping clinical profiles. We evaluated the usefulness of B-scan ultrasonography in distinguishing ON from NAION by measuring diameter of the optic nerve.
  
  
  METHODS
  Consecutive patients with an acute noncompressive unilateral optic neuropathy with relative afferent pupillary defect and onset of visual loss during the last 2 weeks were included. Diagnosis of ON was based on age ≤ 35 years, orbital pain associated with eye movement, and no disk edema, and diagnosis of NAION was based on age ≥ 60 years, no orbital pain associated with eye movement, and presence of disk edema. Age- and gender-matched subjects without ocular disease were selected for comparison. The diameter of the optic nerve was measured by a single radiologist with B-scan ultrasonography.
  
  
  RESULTS
  In ON patients, the mean diameter of the affected nerve was significantly larger than that of the unaffected nerve and also larger than that of the right nerve of young controls; P < 0.05. In NAION patients, however, there was no significant difference between the mean diameter of the affected nerve and of the unaffected nerve or the right nerve of elderly controls; P > 0.05. Also, the diameter of the affected nerve was significantly larger in ON than in AION patients; P < 0.05.
  
  
  CONCLUSIONS
  B-scan ultrasonography is helpful in the early stages of optic neuropathy to distinguish ON from NAION in those cases for which the diagnosis is still uncertain after clinical evaluation.
authors.affiliation: Department of Ophthalmology, Isfahan Eye Research Center, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Alireza
authors.initials: A
authors.lastname: Dehghani
authors.forename: Masoomeh
authors.initials: M
authors.lastname: Giti
authors.forename: Mohamad Reza
authors.initials: MR
authors.lastname: Akhlaghi
authors.forename: Mehdi
authors.initials: M
authors.lastname: Karami
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Salehi