Changes in OCTA measures throughout the day: Diurnal variation or test-retest variability?
Beyza Tekin Altinbay, Emin Kurt, Muhammed Altinisik- Ophthalmology
- General Medicine
Purpose:
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).
Methods:
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.
Results:
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.
Conclusion:
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.