Retinal vasculature is affected in many ocular conditions including diabetic retinopathy, glaucoma and age-related macular degeneration and these alterations can be used as biomarkers. Therefore, it is important to segment and quantify retinal blood vessel characteristics (RBVC) accurately. Using a new automated image processing method applied to optical coherence tomography angiography (OCTA) images we computed the RBVC and compared them between emmetropic (n=40) and ametropic (n=97) subjects. All 137 OCTA images had dimensions of 420x420 pixels corresponding to 6mm x 6mm. The myopia OCTA images were labelled based on a severity scale as mild, moderate, high and very high using standard refractive error classifications. Before image processing, all the images were cropped to 210 X 210 pixels keeping the foveal avascular zone (FAZ) at the centre to quantify the RBVC. The mean ± standard deviation of the Grisan index, a measure of retinal blood vessel tortuosity in the emmetropic, and myopic eye were 0.05 ± 0.02 and 0.05 ± 0.03 respectively. The total vessel distance measures were calculated and the largest were found in emmetropic eyes (45.95 ± 19.54) and shortest in myopic eyes (6.50 ± 5.17). The total number of turning points and inflection points were found to be statistically significant (p<0.05) between control and myopic eyes. However, other RBVC parameters were not statistically different (p=<0.05). We found qualitatively that RBVC changes with increasing severity of the refractive power. Among RBVC parameters, average number of turning points (NTP) decreasing trend with degree of myopia increases.
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