Background/ims 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).
Methods Fifteen 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.
Results The 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)
Conclusions The 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.
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Contributors XY, LS and JC conceived the concept and designed the study. EL collected the data. XY, MK and YH performed the image processing and data analysis. XY drafted the manuscript. DWKW and BT offered administrative or technical support. LS and JC coordinated the project and handled the funding. All contributed to the final manuscript.
Funding The study is funded by National Medical Research Council (grants CG/C010A/2017, OFLCG/004C/2018 and TA/MOH-000249-00/2018) and the Duke-NUS Medical School (Duke-NUS-KP(Coll)/2018/0009A), Singapore.
Disclaimer The sponsor or funding organisation had no role in the design or conduct of this research. The funders had no role in the design and conduct of the study; collection, management, analysis and interpretation of the data; and preparation, review or approval of the manuscript; and decision to submit the manuscript for publication.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. All raw data and measurement results are deidentified participant data, and are available upon reasonable request. Please contact Dr Jacqueline Chua: firstname.lastname@example.org if interested.
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