DOI: 10.1097/iae.0000000000004020 ISSN: 0275-004X

Changes in OCTA measures throughout the day: Diurnal variation or test-retest variability?

Beyza Tekin Altinbay, Emin Kurt, Muhammed Altinisik
  • Ophthalmology
  • General Medicine


To evaluate the repeatability and diurnal variation of the retinal vessel density (VD) and foveal avascular zone (FAZ) parameters using optical coherence tomography angiography (OCTA).


41 healthy individuals were measured twice in the morning and once in the evening. FAZ area, perimetry, foveal density (FD); superficial and deep capillary plexus (SCP, DCP) VD, central macular thickness (CMT) were evaluated with the intraclass correlation coefficient (ICC), coefficient of repeatability (CR) and Bland-Altman plots.


Repeatability was evaluated with two consecutive scans taken in the morning. The CRs (%) was 5.4; 4.3 and 8.8 for the FAZ area, perimetry and FD respectively with excellent ICCs. ICC was poor for parafovea (0.33), whereas excellent for fovea (0.97) in SCP-VD. CR for fovea and parafovea, were 19.19% and 10.43% respectively. ICC values were poor (0.3-0.4) with 10-16% measurement differences in DCP-VD parameters. CRs for CMT were between 1-2% with excellent ICC. The analysis on diurnal variation yielded comparable results.


Except for the parafoveal VD, OCTA is a highly reproducible device for measuring FAZ and VD using 6x6 scans with undilated pupils. However, variation in OCTA parameters observed throughout the day could be attributed to test-retest variation rather than diurnal rhythm.

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