OCT-A Measurement of Retinal Vessel Density: Key Factors Influencing Repeatability
By Lynda Seminara
Selected By: Deepak P. Edward, MD
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.