Yao X, Ke M, Ho Y, et al. - In this investigation involving 15 healthy volunteers, aged 21 and above, with no history of systemic or ocular diseases, researchers sought to compare the retinal vessel diameter measurements obtained from the swept-source optical coherence tomography angiography (OCTA; Plex Elite 9000, Carl Zeiss Meditec, USA) and adaptive optics ophthalmoscope (AOO; RTX1, Imagine Eyes, France). This research was carried out at the Singapore Eye Research Institute between June 2019 and August 2019. The inter-rater agreement has been excellent in both OCTA protocols and AOO for measuring vessel diameters. In general, the diameter of retinal vessels measured from OCTA scans were wider than that obtained from AOO scans. Various OCTA scanning protocols can affect measurements of the vessel's diameter. This needs to be taken into consideration when calculating OCTA measures such as vessel density.