Changes in Choroidal Blood Flow by Diurnal Variation in Healthy Young Adults

Background: Little is known about the diurnal variation in choroidal circulatory dynamics in healthy eyes.Objective: This study aimed to clarify the diurnal variation in choroidal circulatory hemodynamic changes in healthy participants using laser speckle flowgraphy.Methods: This prospective study included the left eye of 14 healthy young adults (21.9 +/- 4.0 years). The mean blur rate, a quantitative index of the relative blood flow velocity, was measured by laser speckle flowgraphy. The macular mean blur rate of choroidal blood flow velocity, subfoveal choroidal thickness, intraocular pressure, systolic blood pressure, diastolic blood pressure, mean blood pressure, and ocular perfusion pressure were evaluated at eight points every 3 h over a 24-h period. In addition, differences in each parameter between daytime and night were also investigated.Results: Intraocular pressure, systolic blood pressure, diastolic blood pressure, mean blood pressure, ocular perfusion pressure, and macular mean blur rate were highest at 6 PM, and subfoveal choroidal thickness was thinnest at 6 PM. There was a significant positive correlation between mean blur rate and intraocular pressure, diastolic blood pressure, and mean blood pressure. Furthermore, intraocular pressure, systolic blood pressure, diastolic blood pressure, mean blood pressure, ocular perfusion pressure, and mean blur rate were significantly higher and choroidal thickness significantly lower during daytime than at night.Conclusion: These results suggest that choroidal circulation hemodynamics change with diurnal variations in systemic circulation involving the autonomic nervous system in healthy eyes.