title: Differentiation between optic disc drusen and optic disc oedema using fundus photography.
abstract: OBJECTIVE
  To describe a funduscopic sign that can be used to differentiate between optic disc drusen (ODD) and optic disc oedema (ODE).
  
  
  METHODS
  A total of 73 eyes from 73 consecutive subjects with disc margin blurring who had been evaluated using spectral-domain optical coherence tomography (SD-OCT) were included. Final diagnosis was made by SD-OCT; ODD was defined by direct visualization of ODD, while ODE was defined by documentation of retinal nerve fibre layer oedema (nasal retinal nerve fibre layer thickness >78.0 μm). Peripapillary retina was selected as a two-disc-diameter-sized square image from the fundus photograph. Using MATLAB software, colour photographs were converted to indexed image of eight colours. Presence of a smooth contour strip between the nasal disc margin and juxtapapillary retina was defined as a halo. Whether the halo could predict the ODD was analysed retrospectively.
  
  
  RESULTS
  The halo sign was detected in 45 eyes (100%) with ODD including one eye with both ODD and ODE. No eyes with ODE alone showed the halo sign. The halo sign implied the presence of ODD (Cohen's kappa = 1.000, p < 0.001) and the absence of ODE (Cohen's kappa = 0.971, p < 0.001). The halo sign showed a good interobserver reliability [ICC (2, 1) = 0.944, 95% confidence interval 0.912-0.964]. SD-OCT images showed that halos represented retinal elevations above ODD.
  
  
  CONCLUSIONS
  In the patients with blurred disc margin, the presence of a halo strongly suggested underlying ODD rather than ODE.
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea.|Department of Ophthalmology, Seoul National University Bundang Hospital, Seongnam, Gyeonggi, Korea.
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Lee
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea.|Department of Ophthalmology, Seoul National University Bundang Hospital, Seongnam, Gyeonggi, Korea.
authors.forename: Se Joon
authors.initials: SJ
authors.lastname: Woo
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea.|Department of Ophthalmology, Seoul National University Bundang Hospital, Seongnam, Gyeonggi, Korea.
authors.forename: Jeong-Min
authors.initials: JM
authors.lastname: Hwang
mesh_terms: D000328:Adult; D003937:Diagnosis, Differential; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009412:Nerve Fibers / Q000473:pathology*; D009898:Optic Disk / Q000473:pathology*; D015594:Optic Disk Drusen / Q000175:diagnosis*; D010211:Papilledema / Q000175:diagnosis*; D010781:Photography / Q000379:methods*; D015203:Reproducibility of Results; D012165:Retinal Ganglion Cells / Q000473:pathology*; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods*
keywords: halo sign; optic disc drusen; optic disc oedema; spectral-domain optical coherence tomography