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  • OCT-A Measurement of Retinal Vessel Density: Key Factors Influencing Repeatability

    By Lynda Seminara
    Selected By: Deepak P. Edward, MD
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    Journal Highlights

    British Journal of Ophthalmology
    Published online Aug. 16, 2017

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    Optical coherence tomography angi­ography (OCT-A) may permit rapid quantification of retinal capillary plexus density in various disease states. Although studies have indicated that OCT-A has potential for excellent reproducibility and repeatability, meth­ods of appraising scan quality have not been clearly defined. Fenner et al. set out to identify key factors affecting the repeatability of OCT-A measurements and noted the importance of ensuring visibility of fine vasculature while mini­mizing motion artifact.

    For this study, the researchers obtained OCT-A images of 44 healthy eyes (44 subjects; mean age, 70 years) during 2 separate clinic visits. Each eye was examined using the Topcon DRI OCT Triton imaging system. Parafoveal vessel density within a 1.5-mm radius centered over the fovea was determined with the built-in tool for assessing superficial and deep retinal plexuses. Repeatability of vessel density was ascertained by intraclass correlation (ICC) and mean variation. Several im­age-quality parameters were evaluated to determine their influence on the repeatability of vessel density measure­ments in each capillary plexus.

    The repeatability of measurements was better for the superficial plexus, a finding that has been reported by other investigators. For the superficial plexus, mean parafoveal vessel density measurements for the first and second visits were 53.3 ± 11.1 and 53.3 ± 10.3, respectively; for the deep plexus, those measurements were 27.3 ± 8.59 and 27.0 ± 8.78, respectively. According to ICC analyses, clear visibility of fine vessels, absence of motion artifact, and a software-derived image-quality score of at least 60 were necessary to obtain good (ICC > 0.6) or excellent (ICC > 0.75) repeatability. Variations in centration and image tilt did not affect measurement repeatability for either plexus.

    The original article can be found here.