Retinal blood flow velocity in metabolic syndrome

Background: Metabolic syndrome (MetS) is characterized by obesity, insulin resistance, dyslipidemia, and hypertension. The Retinal Function Imager (RFI) is a new technique for measuring retinal blood-flow velocity. This study aims to compare retinal blood flow velocity between MetS and healthy subjects. Methods: Twenty eyes of 20 MetS males and 21 eyes of 21 aged-matched healthy males underwent RFI and carotid-femoral pulse wave velocity (PWV) measurement as well as assessment of MetS parameters. The results in MetS and healthy subjects were compared. Results: The average venular velocity in the MetS patients was significantly higher than in the healthy subjects (2.7 ± 0.0 mm/sec versus 2.5 ± 0.0 mm/sec respectively, P = 0.013), following adjustment for age, heart rate and systolic blood pressure. Carotid-femoral PWV was higher in the MetS population than the healthy controls (10.3 ± 1.2 mm/sec versus 9.3 ± 1.5 mm/sec respectively, P = 0.005). The diastolic blood pressure and MAP were correlated strongly with the arterial blood flow velocities in healthy subjects (r = 0.503, P = 0.020 and r = 0.474, P = 0.030 respectively) but not in MetS subjects. Conclusions: The RFI was able to distinguish between the retinal blood flow of normal and MetS subjects. Higher venular blood flow velocity and the poor correlation between velocity and blood pressure of MetS subjects suggest that MetS causes microvascular damage.