title: Optical Coherence Tomography Angiography for Anterior Segment Vasculature Imaging.
abstract: OBJECTIVE
  To evaluate the application of an optical coherence tomography angiography (OCTA) system adapted for the assessment of anterior segment vasculature.
  
  
  METHODS
  Cross-sectional, observational study.
  
  
  METHODS
  Consecutive subjects with normal eyes on slit-lamp clinical examination and patients with abnormal corneal neovascularization.
  
  
  METHODS
  All scans were performed using a commercially available AngioVue OCTA system (Optovue, Inc., Fremont, CA) using an anterior segment lens adapter and the split-spectrum amplitude decorrelation angiography algorithm. Each subject underwent scans from 4 quadrants (superior, inferior, nasal, and temporal) in each eye by 2 trained, independent operators.
  
  
  METHODS
  Analysis of signal strength, image quality, and reproducibility of corneal vascular measurements was performed.
  
  
  RESULTS
  In our study of 20 normal subjects (10 men, 10 women; mean age, 25.3±7.8 years), we found good repeatability (κ coefficient, 0.76) for image quality score and good interobserver agreement for vasculature measurements (intraclass coefficient, 0.94). After optimization of the angiography scan protocol, vascular measurements within the regions of interest were compared in the superior versus inferior quadrants (mean vascular loops, 3.34±1.16 vs. 3.12 ± 0.90 [P = 0.768]; segment-to-loop ratio, 4.18±0.71 vs. 4.32±0.87 [P = 0.129]; fractal dimension [Df] value, 1.78±0.06 vs. 1.78±0.06 [P = 0.94]; vascular loop area, 25.9±14.5 vs. 25.9±10.7 × 10(-3) mm(2) [P = 0.21]) and nasal versus temporal quadrant (mean vascular loops, 2.89±0.98 vs. 3.57±0.99 [P < 0.001]; segment-to-loop ratio, 3.94±0.69 vs. 4.55±0.78 [P = 0.897]; Df value, 1.78±0.06 vs. 1.77±0.06 [P = 0.14]; vascular loop area, 29.7±15.7 vs. 22.1±7.1 × 10(-3) mm(2) [P = 0.38]. We then used the established OCTA scanning protocol to visualize abnormal vasculature successfully in 5 patients with various corneal pathologic features, including graft-associated neovascularization, postherpetic keratitis scarring, lipid keratopathy, and limbal stem cell deficiency.
  
  
  CONCLUSIONS
  This preliminary study describes a method for acquiring OCTA images of the cornea and limbal vasculature with substantial consistency. This technique may be useful for the objective evaluation of corneal neovascularization in the future.
authors.affiliation: Department of Cornea and External Eye Diseases, Singapore Eye Research Institute, Singapore National Eye Center, Singapore; Department of External Eye Diseases, Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom. Electronic address: marcus.ang.h.n@snec.com.sg.
authors.forename: Marcus
authors.initials: M
authors.lastname: Ang
authors.affiliation: Department of Medical Retina, Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.
authors.forename: Dawn A
authors.initials: DA
authors.lastname: Sim
authors.affiliation: Department of Medical Retina, Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom; Institute of Ophthalmology, University College London, United Kingdom.
authors.forename: Pearse A
authors.initials: PA
authors.lastname: Keane
authors.affiliation: Department of Cornea and External Eye Diseases, Singapore Eye Research Institute, Singapore National Eye Center, Singapore; Department of Ophthalmology, National University Hospital, Singapore.
authors.forename: Chelvin C A
authors.initials: CC
authors.lastname: Sng
authors.affiliation: Department of Medical Retina, Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Egan
authors.affiliation: Department of Medical Retina, Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.
authors.forename: Adnan
authors.initials: A
authors.lastname: Tufail
authors.affiliation: Department of External Eye Diseases, Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom; Institute of Ophthalmology, University College London, United Kingdom.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Wilkins
mesh_terms: D000328:Adult; D000869:Anterior Eye Segment / Q000098:blood supply*; D016510:Corneal Neovascularization / Q000503:physiopathology; D003430:Cross-Sectional Studies; D003952:Diagnostic Imaging / Q000379:methods; D005260:Female; D005451:Fluorescein Angiography; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000502:physiology; D008875:Middle Aged; D011625:Pterygium / Q000503:physiopathology; D012039:Regional Blood Flow / Q000502:physiology*; D041623:Tomography, Optical Coherence; D055815:Young Adult