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Updated: Mar 12, 2026
Retinal Vascular Reactivity as Assessed by Optical Coherence Tomography Angiography
Published on: March 26, 2020
Retinal vessel calibre measurements by optical coherence tomography angiography
Khalil Ghasemi Falavarjani1,2,3, Mayss Al-Sheikh1,2, Fatemeh Darvizeh2,4
1Department of Ophthalmology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA.
Purpose:
To compare the vessel calibre measurements between optical coherence tomography angiography (OCTA) and colour fundus photography.
Methods:
In this retrospective comparative study, OCTA and colour fundus images of healthy eyes and eyes with optic atrophy were evaluated. The colour fundus image was registered manually using Image J software to the OCTA image of the optic disc. Two independent graders measured the vessel calibre of the widest vein and artery in each peripapillary quadrant on a 3.4 mm diameter circle centred on the optic disc in the same location on both images. The difference in vessel calibre between the two techniques was assessed.
Results:
A total of 312 vessels from 29 healthy eyes and 20 eyes with atrophic optic discs were included. There was a high level of agreement between graders for measurement of vessel calibre in both colour fundus (intraclass correlation coefficient=0.93, coefficient of variation=0.07) and OCTA images (intraclass correlation coefficient=0.94, coefficient of variation=0.05). The mean vessel calibre in colour fundus images (94.5±23.2 µm) and OCT images (112.2±26.1 µm) was correlated (r=0.8, p<0.001), but the difference was statistically significant (mean difference: 17.6±1.5 µm, p<0.001). This difference was evident for both arteries (mean difference: 18.2±16.3 µm, p<0.001) and veins (mean difference: 15.1±16.2 µm, p<0.001) individually, with a similar magnitude of difference for both vessel types (p=0.08). In addition, the magnitude of difference between imaging modalities was similar in atrophic and healthy discs (17.1±15.9 vs 18.4±15.2 µm, respectively, p=0.4). The difference, however, was significantly higher in vessels with a calibre of ≤94.5 compared with larger vessels (19.3±16.3 vs 15.6±14.4 µm, respectively, p=0.02).
Conclusions:
Vessel calibre measurements were significantly larger in OCTA images compared with colour fundus photographs, particularly for smaller vessels. These differences may need to be accounted for when using OCTA-derived metrics.
