title: Objective detection of retinal vessel pulsation.
abstract: OBJECTIVE
  Retinal venous pulsation detection is a subjective sign, which varies in elevated intracranial pressure, venous obstruction and glaucoma. To date no method can objectively measure and identify pulsating regions.
  
  
  METHODS
  Using high resolution video-recordings of the optic disk and retina we measured fluctuating light absorption by haemoglobin during pulsation. Pulsation amplitude was calculated from all regions of the retinal image video-frames in a raster pattern. Segmented retinal images were formed by objectively selecting regions with amplitudes above a range of threshold values. These were compared to two observers manually drawing an outline of the pulsating areas while viewing video-clips in order to generate receiver operator characteristics.
  
  
  RESULTS
  216,515 image segments were analysed from 26 eyes in 18 research participants. Using data from each eye, the median area under the receiver operator curve (AU-ROC) was 0.95. With all data analysed together the AU-ROC was 0.89. We defined the ideal threshold amplitude for detection of any pulsating segment being that with maximal sensitivity and specificity. This was 5 units (95% confidence interval 4.3 to 6.0) compared to 12 units before any regions were missed. A multivariate model demonstrated that ideal threshold amplitude increased with increased variation in video-sequence illumination (p = 0.0119), but between the two observers (p = 0.0919) or other variables.
  
  
  CONCLUSIONS
  This technique demonstrates accurate identification of retinal vessel pulsating regions with no areas identified manually being missed with the objective technique. The amplitude values are derived objectively and may be a significant advance upon subjective ophthalmodynamometric threshold techniques.
authors: Lions Eye Institute, University of Western Australia, Nedlands, Australia.
authors: William H
authors: WH
authors: Morgan
authors: Department of Ophthalmology, Manukau Health, Auckland, New Zealand.
authors: Anmar
authors: A
authors: Abdul-Rahman
authors: Lions Eye Institute, University of Western Australia, Nedlands, Australia.
authors: Dao-Yi
authors: DY
authors: Yu
authors: Statistics and Bioinformatics Group, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
authors: Martin L
authors: ML
authors: Hazelton
authors: Statistics and Bioinformatics Group, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
authors: Brigid
authors: B
authors: Betz-Stablein
authors: Neurofinity, School of Surgery, University of Western Australia, Nedlands, Australia.
authors: Christopher R P
authors: CR
authors: Lind
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009898:Optic Disk / Q000098:blood supply; D011673:Pulsatile Flow; D012169:Retinal Vein / Q000294:innervation / Q000502:physiology*; D014741:Video Recording; D055815:Young Adult
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