Upon investigating the diurnal changes of choroidal sublayer perfusion in normal eyes and identifying influencing factors using optical coherence tomography angiography (OCT-A), German researchers found that OCTA-based analysis demonstrated significant diurnal variations in choroidal sublayer perfusion.

The prospective study evaluated 22 healthy volunteers who underwent repeated measurements of subfoveal choroidal thickness with enhanced-depth-imaging OCT as well as perfusion of choroidal vascular sublayers using OCT-A at 7am, 12pm, 4pm and 8pm. The team looked into possible interactions between diurnal variations and other factors, such as mean arterial pressure, gender and age.

The study authors observed a significant pattern of diurnal variation for subfoveal choroidal thickness as well as perfusion of Sattler's layer and Haller's layer. They also noted subfoveal choroidal thickness was thicker in the morning (348μm) and thinner in the evening (310μm). 

The researchers went on to discover that both Sattler's layer and Haller's layer showed an association with the time of day, increasing from morning (64% and 76%, respectively) to afternoon (66% and 77%, respectively) before decreasing again in the evening (64% and 76%, respectively). They note that Haller's layer changes were significantly associated with fluctuations in mean arterial pressure. They did not detect any significant differences in regards to gender; however, older participants (≥60 years) had fewer diurnal changes. These finding suggest researchers and clinicians should account for the time of day when comparing longitudinal OCT-A data, the authors said in the study.