CHANGES IN OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY MEASURES THROUGHOUT THE DAY: Diurnal Variation or Test-Retest...

Area of Science:

• Ophthalmology
• Medical Imaging
• Retinal Imaging

Background:

• Optical coherence tomography angiography (OCTA) is a key imaging modality in ophthalmology.
• Assessing the repeatability and diurnal variations of OCTA parameters is crucial for clinical application.

Purpose of the Study:

• To evaluate the repeatability and diurnal variation of retinal vessel density and foveal avascular zone parameters using OCTA.

Main Methods:

• Forty-one healthy individuals underwent OCTA measurements twice in the morning and once in the evening.
• Parameters assessed included foveal avascular zone area, perimetry, foveal density, superficial and deep capillary plexus vessel density, and central macular thickness.
• Intraclass correlation coefficient, coefficient of repeatability, and Bland-Altman plots were used for analysis.

Main Results:

• High repeatability was observed for foveal avascular zone area, perimetry, and foveal density (excellent ICC).
• Superficial capillary plexus vessel density showed excellent repeatability for the fovea but poor for the parafovea.
• Deep capillary plexus vessel density demonstrated poor repeatability, while central macular thickness showed excellent repeatability (1-2% CoR). Diurnal variation analysis yielded comparable results.

Conclusions:

• OCTA is a highly reproducible device for measuring foveal avascular zone and vessel density with 6x6 scans and undilated pupils.
• Parfoveal vessel density is an exception, showing lower reproducibility.
• Observed diurnal variations in OCTA parameters are likely due to test-retest variability rather than a true diurnal rhythm.