The purpose of this study was to evaluate the diurnal variation of blood flow index and vascular density in superficial and deep plexus of retina and choroid and optic nerve head in healthy eyes to show if diurnal variation may have role in alteration in blood flow index and vascular density due to physiologic changes of body blood flow using optical coherence tomography angiography (OCTA).

34 healthy eyes of 17 volunteer were scanned by an RTVue XR Avanti; Optovue with OCTA using the split-spectrum amplitude-decorrelation angiography algorithm technique. The superficial and deep plexus of retina and choroid and optic nerve head were measured in 3×3 and 8×8 mm scans.

A total of 34 eyes of 17 healthy participants with a mean age of 27 years old were examined. The flow index of superficial and deep plexus of retina was not different over time, but flow index of choroid in 8×8 scans was different over day with P value of 0.047(P-values <0.05 were considered statistically significant). The vascular density of deep layer of foveal and parafoveal area was significantly different with p Value of 0.021 and 0.032. Vascular density of peripapillary area and deep layer of whole was statistically different too with p Value respectively 0.032 and 0.042

There is no difference in blood flow of retina in different hours of day but on the other hand choroidal blood flow in 8 millimeters and vascular density of fovea and deep parafoveal and peripapillary area and deep whole region changes significantly over different hours of day and it is important in assessment of choroid and retinal disease which are based on blood flow index and vascular density changes. This reminds clinicians to perform OCTA at the same time of day to avoid normal diurnal variations and mistakes in interpretation of tests.