Comparison of retinal vessel diameter measurements from swept-source OCT angiography and adaptive optics ophthalmoscope

Abstract

Background/imsTo 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).MethodsFifteen healthy subjects, 67% women, mean age (SD) 30.87 (6.19) years, were imaged using OCTA and AOO by a single experienced operator on the same day. Each eye was scanned using two OCTA protocols (3×3 mm2 and 9×9 mm2) and two to five AOO scans (1.2×1.2 mm2). The OCTA and AOO scans were scaled to the same pixel resolution. Two independent graders measured the vessel diameter at the same location on the region-of-interest in the three coregistered scans. Differences in vessel diameter measurements between the scans were assessed.ResultsThe inter-rater agreement was excellent for vessel diameter measurement in both OCTA protocols (ICC=0.92) and AOO (ICC=0.98). The measured vessel diameter was widest from the OCTA 3×3 mm2 (55.2±16.3 µm), followed by OCTA 9×9 mm2 (54.7±14.3 µm) and narrowest by the AOO (50.5±15.6 µm; p<0.001). Measurements obtained from both OCTA protocols were significantly wider than the AOO scan (OCTA 3×3 mm2: mean difference Δ=4.7 µm, p<0.001; OCTA 9×9 mm2: Δ=4.2 µm, p<0.001). For vessels >45 µm, it appeared to be larger in OCTA 3×3 mm2 scan than the 9×9 mm2 scan (Δ=1.9 µm; p=0.005), while vessels <45 µm appeared smaller in OCTA 3×3 mm2 scan (Δ=−1.3 µm; p=0.009)ConclusionsThe diameter of retinal vessels measured from OCTA scans were generally wider than that obtained from AOO scans. Different OCTA scan protocols may affect the vessel diameter measurements. This needs to be considered when OCTA measures such as vessel density are calculated.

Retinal microvasculature dysfunction is associated with Alzheimer’s disease and mild cognitive impairment

“…Retinal vessels measured from fundus photos are considerably larger in diameter than those obtained from OCTA [4]. Also, the diameters of retinal vessels measured with OCTA are in good agreement with the ground truth as obtained with adaptive optics ophthalmoscope [57]. Therefore, the lack of large vessel changes despite capillary changes suggests that microvascular alterations precede large vessel changes.…”

Combining OCT and OCTA for Focal Structure–Function Modeling in Early Primary Open-Angle Glaucoma

“…48 Vascular parameters were obtained from OCTA, which does not provide an actual quantification of blood flow but does provide a visualization of ocular perfusion, which has been shown to be a close approximation of vascular characteristics. 12 Assessments of structure–function relationships were limited to linear mixed models, 41 and other approaches were not considered. Only subjects from a single ethnicity were included in this study.…”

“… 8 , 9 OCT angiography (OCTA) is a recent technique 10 , 11 for the visualization of retinal perfusion to the level of capillaries. 12 In glaucoma, the usefulness of OCTA-based vascular metrics has been demonstrated in the discrimination of diseased eyes from healthy eyes. 13 – 15 Relating structural and, increasingly, vascular 16 – 25 changes with functional loss of vision in glaucoma is referred to as the structure–function relationship.…”

Methods to measure blood flow and vascular reactivity in the retina

“…The determination of the vessel diameter is an important feature to analyze retinal blood flow. It has been shown that the diameters of retinal vessels measured from OCTA scans were generally wider than with measurements obtained from adaptive optics ophthalmoscope (AOO) (100) or fundus photographs (101) regardless of scan protocols and vessel types. Reasons could be the oversampling rate of the OCTA system, the poorer lateral resolution compared with the AOO system or the effect of binarization (100).…”