title: Automated Quantification of Capillary Nonperfusion Using Optical Coherence Tomography Angiography in Diabetic Retinopathy.
abstract: OBJECTIVE
  Macular ischemia is a key feature of diabetic retinopathy (DR). Quantification of macular ischemia has potential as a biomarker for DR.
  
  
  OBJECTIVE
  To assess the feasibility of automated quantification of capillary nonperfusion as a potential sign of macular ischemia using optical coherence tomography (OCT) angiography.
  
  
  METHODS
  An observational study conducted in a tertiary, subspecialty, academic practice evaluated macular nonperfusion with 6 × 6-mm OCT angiography obtained with commercially available 70-kHz OCT and fluorescein angiography (FA). The study was conducted from January 22 to September 18, 2014. Data analysis was performed from October 1, 2014, to April 7, 2015. Participants included 12 individuals with normal vision serving as controls and 12 patients with various levels of DR.
  
  
  METHODS
  Preplanned primary measures were parafoveal and perifoveal vessel density, total avascular area, and foveal avascular zone as detected with 6 × 6-mm OCT angiography and analyzed using an automated algorithm. Secondary measures included the agreement of the avascular area between the OCT angiogram and FA.
  
  
  RESULTS
  Compared with the 12 healthy controls (11 women; mean [SD] age, 54.2 [14.2] years), the 12 participants with DR (4 women; mean [SD] age, 55.1 [12.1] years) had reduced parafoveal and perifoveal vessel density by 12.6% (95% CI, 7.7%-17.5%; P < .001) and 10.4% (95% CI, 6.8%-14.1%; P < .001), respectively. Total avascular area and foveal avascular zone area were greater in eyes with DR by 0.82 mm2 (95% CI, 0.65-0.99 mm2; P = .02) and 0.16 mm2 (95% CI, 0.05-0.28 mm2; P < .001). The agreement between the vascular areas in the OCT angiogram and FA had a κ value of 0.45 (95% CI, 0.21-0.70; P < .001). Total avascular area in the central 5.5-mm-diameter area distinguished eyes with DR from control eyes with 100% sensitivity and specificity.
  
  
  CONCLUSIONS
  Avascular area analysis with an automated algorithm using OCT angiography, although not equivalent to FA, detected DR reliably in this small pilot study. Further study is necessary to determine the usefulness of the automated quantification in clinical practice.
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Hwang
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: Simon S
authors.initials: SS
authors.lastname: Gao
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: Liang
authors.initials: L
authors.lastname: Liu
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: Andreas K
authors.initials: AK
authors.lastname: Lauer
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: Steven T
authors.initials: ST
authors.lastname: Bailey
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: Christina J
authors.initials: CJ
authors.lastname: Flaxel
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: David J
authors.initials: DJ
authors.lastname: Wilson
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: David
authors.initials: D
authors.lastname: Huang
authors.affiliation: Casey Eye Institute, Oregon Health & Science University, Portland, Oregon.
authors.forename: Yali
authors.initials: Y
authors.lastname: Jia
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001331:Automation; D016022:Case-Control Studies; D003930:Diabetic Retinopathy / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D005451:Fluorescein Angiography / Q000379:methods*; D006801:Humans; D007511:Ischemia / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008268:Macular Degeneration / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D011859:Radiography; D012171:Retinal Vessels / Q000503:physiopathology*; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D041623:Tomography, Optical Coherence / Q000379:methods* / Q000706:statistics & numerical data