Falavarjani KG, et al. - Among 24 healthy eyes and 20 eyes with diabetic macular oedema (DMO), researchers assessed the impact of segmentation error on vessel density measurements in this prospective, comparative, non-interventional study. In healthy and diabetic eyes, respectively, the rate of segmentation error was 33% and 100%. In DMO, the mean absolute change in superficial and deep inner retinal thickness was statistically significantly higher. In all eyes with DMO and in one-third of healthy eyes, misidentification of retinal layers and consequent vessel density measurement error occurred. In the optical coherence tomography angiography vessel density measurements, particularly in the presence of macular oedema, the segmentation error should be checked and manually corrected.