title: Distinguishing ischaemic optic neuropathy from optic neuritis by ganglion cell analysis.
abstract: OBJECTIVE
  To determine whether a pattern of altitudinal ganglion cell loss, as detected and measured by optical coherence tomography (OCT), can be used to distinguish non-arteritic ischaemic optic neuropathy (NAION) from optic neuritis (ON) during the acute phase, and whether the rate or severity of ganglion cell loss differs between the two diseases.
  
  
  METHODS
  We performed a retrospective, case-control study of 44 patients (50 eyes) with ON or NAION and 44 age-matched controls. Non-arteritic ischaemic optic neuropathy and ON patients had OCT at presentation and four consecutive follow-up visits. Controls had OCT at one point in time. The ganglion cell complex (GCC) was evaluated in the macula, and the retinal nerve fibre layer (RNFL) was evaluated in the peripapillary region. Ganglion cell complex thickness, RNFL thickness and GCC mean superior and inferior hemispheric difference were compared between NAION and ON patients at each time-point using unpaired t-tests and between disease and control subjects at first measurement using paired t-tests.
  
  
  RESULTS
  Mean time from onset of symptoms to initial presentation was 10.7 ± 6.6 days in NAION and 11.7 ± 8.6 days in ON (p = 0.67). There was a significantly greater vertical hemispheric difference in GCC thickness in NAION patients than ON patients at all time-points (5.5-10.7 μm versus 3.1-3.6 μm, p = 0.01-0.049). Mean GCC thickness was significantly decreased at less than 2 weeks after onset in NAION compared to age-matched controls (72.1 μm versus 82.1 μm, p < 0.001), as well as in ON compared to age-matched controls (74.3 μm versus 84.5 μm, p < 0.001). Progression and severity of GCC and RNFL loss did not differ significantly between NAION and ON.
  
  
  CONCLUSIONS
  A quantitative comparison of mean superior and inferior hemispheric GCC thickness with OCT may be used to distinguish NAION from ON.
authors.affiliation: New England Eye Center, Tufts University School of Medicine, Tufts Medical Center, Boston, Massachusetts, USA.
authors.forename: Natalie
authors.initials: N
authors.lastname: Erlich-Malona
authors.affiliation: New England Eye Center, Tufts University School of Medicine, Tufts Medical Center, Boston, Massachusetts, USA.|Dysautonomia Center, New York University Schools of Medicine, NYU Langone Medical Center, New York, USA.|Ophthalmology Department, Pontifical Catholic University of Chile, Santiago, Chile.
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Mendoza-Santiesteban
authors.affiliation: New England Eye Center, Tufts University School of Medicine, Tufts Medical Center, Boston, Massachusetts, USA.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Hedges
authors.affiliation: New England Eye Center, Tufts University School of Medicine, Tufts Medical Center, Boston, Massachusetts, USA.
authors.forename: Nimesh
authors.initials: N
authors.lastname: Patel
authors.affiliation: New England Eye Center, Tufts University School of Medicine, Tufts Medical Center, Boston, Massachusetts, USA.
authors.forename: Caitlin
authors.initials: C
authors.lastname: Monaco
authors.affiliation: New England Eye Center, Tufts University School of Medicine, Tufts Medical Center, Boston, Massachusetts, USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Cole
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009902:Optic Neuritis / Q000175:diagnosis*; D018917:Optic Neuropathy, Ischemic / Q000175:diagnosis*; D012165:Retinal Ganglion Cells / Q000473:pathology*; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence
keywords: OCT; ganglion cell complex; ischaemic optic neuropathy; optic neuritis; retinal nerve fibre layer