title: An easy method to differentiate retinal arteries from veins by spectral domain optical coherence tomography: retrospective, observational case series.
abstract: BACKGROUND
  Recently it was shown that retinal vessel diameters could be measured using spectral domain optical coherence tomography (OCT). It has also been suggested that retinal vessels manifest different features on spectral domain OCT (SD-OCT) depending on whether they are arteries or veins. Our study was aimed to present a reliable SD-OCT assisted method of differentiating retinal arteries from veins.
  
  
  METHODS
  Patients who underwent circular OCT scans centred at the optic disc using a Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) were retrospectively reviewed. Individual retinal vessels were identified on infrared reflectance (IR) images and given unique labels for subsequent grading. Vessel types (artery, vein or uncertain) assessed by IR and/or fluorescein angiography (FA) were referenced as ground truth. From OCT, presence/absence of the hyperreflective lower border reflectivity feature was assessed. Presence of this feature was considered indicative for retinal arteries and compared with the ground truth.
  
  
  RESULTS
  A total of 452 vessels from 26 eyes of 18 patients were labelled and 398 with documented vessel type (302 by IR and 96 by FA only) were included in the study. Using SD-OCT, 338 vessels were assigned a final grade, of which, 86.4% (292 vessels) were classified correctly. Forty three vessels (15 arteries and 28 veins) that IR failed to differentiate were correctly classified by SD-OCT. When using only IR based ground truth for vessel type the SD-OCT based classification approach reached a sensitivity of 0.8758/0.9297, and a specificity of 0.9297/0.8758 for arteries/veins, respectively.
  
  
  CONCLUSIONS
  Our method was able to classify retinal arteries and veins with a commercially available SD-OCT alone, and achieved high classification performance. Paired with OCT based vessel measurements, our study has expanded the potential clinical implication of SD-OCT in evaluation of a variety of retinal and systemic vascular diseases.
authors.forename: Yanling
authors.initials: Y
authors.lastname: Ouyang
authors.forename: Qing
authors.initials: Q
authors.lastname: Shao
authors.forename: Dirk
authors.initials: D
authors.lastname: Scharf
authors.forename: Antonia M
authors.initials: AM
authors.lastname: Joussen
authors.affiliation: Charité-Universitätsmedizin Berlin, Department of Ophthalmology, Berlin, Germany. florian.heussen@gmail.com.
authors.forename: Florian M
authors.initials: FM
authors.lastname: Heussen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005451:Fluorescein Angiography; D005500:Follow-Up Studies; D005654:Fundus Oculi; D006801:Humans; D008297:Male; D008875:Middle Aged; D009887:Ophthalmoscopy; D012372:ROC Curve; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology*; D012164:Retinal Diseases / Q000175:diagnosis*; D012169:Retinal Vein / Q000473:pathology*; D012189:Retrospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult