title: Retinal nerve fiber layer and future risk of multiple sclerosis.
abstract: BACKGROUND
  Optical coherence tomography (OCT)--measured retinal nerve fiber layer (RNFL) values may represent a surrogate biomarker for axonal integrity in multiple sclerosis (MS). The purpose of this study was to determine whether RNFL measurements obtained within two years of an optic neuritis (ON) event distinguish patients at increased risk of developing clinically-definite MS (CDMS).
  
  
  METHODS
  Fifty consecutively sampled patients who experienced a single ON event were followed prospectively for a mean period of 34 months with OCT testing. Values of RNFL in clinically-affected and non-affected eyes were compared between patients who developed CDMS and those that did not develop MS after ON.
  
  
  RESULTS
  Twenty-one patients (42%) developed CDMS during the course of the study, with a mean conversion time of 27 months. Mean RNFL values were thinner in the clinically-affected eyes of non-MS patients than CDMS eyes after one year (p = 0.0462) due to more severe ON events in the former. By year two, CDMS patients manifested more recurrent ON events and RNFL thinning than non-MS patients. Temporal RNFL values were thinner in the non-affected eyes of CDMS patients with a trend towards significance (p = 0.1302).
  
  
  CONCLUSIONS
  Our results indicate that RNFL thickness does not reliably distinguish patients at higher risk of converting to CDMS after ON. The severity of ON has a greater effect on RNFL thickness than risk of CDMS at one year. The CDMS patients demonstrate progressive RNFL thinning likely due to recurrent sub-clinical ON events, which may help differentiate them from non-MS patients over time.
authors.affiliation: Hotchkiss Brain Institute, University of Calgary, Department of Clinical Neurosciences, Calgary, Alberta, Canada.
authors.forename: Fiona
authors.initials: F
authors.lastname: Costello
authors.forename: William
authors.initials: W
authors.lastname: Hodge
authors.forename: Y Irene
authors.initials: YI
authors.lastname: Pan
authors.forename: Luanne
authors.initials: L
authors.lastname: Metz
authors.forename: Randy H
authors.initials: RH
authors.lastname: Kardon
mesh_terms: D000293:Adolescent; D000328:Adult; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009103:Multiple Sclerosis / Q000175:diagnosis / Q000473:pathology*; D009412:Nerve Fibers / Q000473:pathology*; D009902:Optic Neuritis / Q000175:diagnosis / Q000473:pathology*; D011446:Prospective Studies; D012165:Retinal Ganglion Cells / Q000166:cytology / Q000473:pathology; D012307:Risk Factors; D041623:Tomography, Optical Coherence