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Br J Ophthalmol 2005;89:1192-1195 doi:10.1136/bjo.2004.065169
  • Clinical science
    • Extended reports

Impact of simulated light scatter on scanning laser Doppler flowmetry

  1. S T Venkataraman1,
  2. C Hudson1,2,
  3. E Harvey3,
  4. J G Flanagan1,2
  1. 1Multi-Disciplinary Laboratory for the Research of Sight-Threatening Diabetic Retinopathy, School of Optometry, University of Waterloo, Waterloo, Ontario, Canada
  2. 2Department of Ophthalmology and Vision Science, University of Toronto, Ontario, Canada
  3. 3Department of Statistics and Actuarial Science, University of Waterloo, Waterloo, Ontario, Canada
  1. Correspondence to: Dr C Hudson School of Optometry, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada; chudsonscimail.uwaterloo.ca
  • Accepted 1 April 2005

Abstract

Aim: To determine the impact of simulated light scatter on scanning laser Doppler flowmetry (SLDF) assessment of retinal capillary blood flow and retinal image quality.

Methods: One eye of 10 normal subjects (mean (SD) age 24 (1.7) years, range 22–27) was randomly selected. Varying concentrations of polystyrene microspheres were suspended in optically clear cells to simulate light scatter. The microsphere concentrations used were 0.05%, 0.03%, 0.02%, 0.01%, and a cell containing only water. LogMAR visual acuity and contrast sensitivity were measured both with and without cells. Optimal focus and alignment was established by acquiring three SLDF images each of the optic nerve head (ONH) and of the macula using the Heidelberg retina flowmeter (HRF) with no cell in place. SLDF images were subsequently acquired with each of the light scatter cells mounted in front of the HRF. The group mean retinal capillary blood flow was compared using repeated measures analysis of variance (reANOVA) as a function of microsphere concentration.

Results: Retinal capillary blood flow increased significantly in the ONH, nasal macula, fovea, and temporal macula with increasing microsphere concentration (p<0.0001). Using Dunnett’s post hoc test, retinal capillary blood flow was found to be significantly increased relative to the no cell condition for the 0.03% and 0.05% cell concentrations.

Conclusions: Simulated light scatter produces an artifactual increase in retinal capillary blood flow. The impact of cataract on SLDF measurements has yet to be determined.

Footnotes

  • This work was funded by the Canadian Institutes of Health Research and by a Premier’s Research Excellence Award (recipient CH).

  • Competing interests: none declared

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