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S.T. Venkataraman, C. Hudson, E. Harvey, J.G. Flanagan; Light Scatter and Scanning Laser Doppler Flowmetry Assessment . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2560.
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Purpose: To determine the impact of simulated light scatter on scanning laser Doppler flowmetry (SLDF) assessment of retinal capillary blood flow and image quality. Methods: Ten normal subjects (mean age 24years, SD 1.7, range 22–27) participated in the study. The study eye was randomly selected in each subject. Varying concentrations of polystyrene microspheres (Polybead ® Polysciences Inc., USA) 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 was measured both with and without the cells. Optimal focus and alignment was established by acquiring 3 SLDF images each of the optic nerve head (ONH) and of the macula using the Heidelberg Retina Flowmeter (HRF) with no cell in place. Subsequently, SLDF images were 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 ANOVA as a function of microsphere concentration. Results: The baseline group mean capillary blood flow values for the ONH, nasal macula, fovea and temporal macula were 226.68 a.u (SD 191.63), 176.52 a.u (SD 39.46), 192.65 a.u (SD 53.92), and 163.89 a.u (SD 83.11), respectively. Retinal capillary blood flow was significantly higher in the ONH, nasal macula, fovea and temporal macula with increase in microsphere concentration (p<0.0001). Using Fisher’s least significant difference post hoc test, retinal capillary blood flow was found to significantly increase relative to baseline for the 0.03% and 0.05% cell concentrations. Conclusions: An artifactual increase in capillary blood flow in all areas of the retina and ONH was produced by the simulated light scatter model. Caution needs to be exercised in the interpretation of retinal capillary blood flow measurements in patients with cataract.
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