title: Quantifying axonal loss after optic neuritis with optical coherence tomography.
abstract: OBJECTIVE
  To determine to what degree changes in retinal nerve fiber layer (RNFL) thickness after optic neuritis (ON) correlate with either visual recovery or impairment.
  
  
  METHODS
  ON can cause visible defects within the RNFL, which can be quantified using optical coherence tomography (OCT). It may be possible to predict visual recovery by measuring RNFL loss after ON. Fifty-four patients underwent repeated evaluations with optical coherence tomography and standardized ophthalmic testing after ON. Regression analyses were used to determine the relationship between RNFL thickness and visual function.
  
  
  RESULTS
  Thinning of the RNFL was seen in the majority of patients (74%), and it tended to occur within 3 to 6 months of ON. The average RNFL value was thinner (p<0.0001) in the affected (78 microm) compared with the unaffected eye (100 microm). Patients with incomplete visual recovery demonstrated greater RNFL loss after ON. Regression analyses demonstrated a threshold of RNFL thickness (75 microm), below which RNFL measurements predicted persistent visual dysfunction.
  
  
  CONCLUSIONS
  Determination of RNFL thickness may predict visual recovery after ON, and lower RNFL values correlate with impaired visual function. Optical coherence tomography may have a potential role as a surrogate marker for axonal integrity within the optic nerve among patients with ON.
authors.affiliation: Division of Neurology, Ottawa, Ontario Canada. fcostello@ottawahospital.on.ca
authors.forename: Fiona
authors.initials: F
authors.lastname: Costello
authors.forename: Stuart
authors.initials: S
authors.lastname: Coupland
authors.forename: William
authors.initials: W
authors.lastname: Hodge
authors.forename: Gianni R
authors.initials: GR
authors.lastname: Lorello
authors.forename: Jeannie
authors.initials: J
authors.lastname: Koroluk
authors.forename: Y Irene
authors.initials: YI
authors.lastname: Pan
authors.forename: Mark S
authors.initials: MS
authors.lastname: Freedman
authors.forename: David H
authors.initials: DH
authors.lastname: Zackon
authors.forename: Randy H
authors.initials: RH
authors.lastname: Kardon
mesh_terms: D000293:Adolescent; D000328:Adult; D001369:Axons / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009410:Nerve Degeneration / Q000175:diagnosis* / Q000209:etiology; D009902:Optic Neuritis / Q000150:complications / Q000473:pathology*; D011379:Prognosis; D011446:Prospective Studies; D020127:Recovery of Function; D012160:Retina / Q000473:pathology*; D041623:Tomography, Optical Coherence; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology; D014787:Vision Tests; D014794:Visual Fields