The prevalence of diabetes mellitus (DM) is rapidly increasing worldwide, with low-and-middle income countries bearing the heaviest burden. In these countries, majority of newly diagnosed DM is incidental, with many new patients unaware of their prior glycaemic status; which increases the likelihood that they may present with DM-related complications, like diabetic retinopathy (DR). The mechanisms underlying the development of diabetic retinopathy are still not fully understood, although elevated glucose levels are thought to be responsible for alterations in retinal vessel architecture, leading to perfusion abnormalities.
The current study sought to determine the relationship between hemodynamic flow in the central retinal artery and long-term glycaemic control as measured by serum haemoglobin A1c.
This was a cross-sectional study involving 140 diabetic patients attending an outpatients DM clinic at Mulago National Referral hospital. Color Doppler imaging (CDI) of the orbit was used to determine hemodynamic flow parameters (end-diastolic velocity (EDV), peak-systolic velocity (PSV), resistivity index (RI), and pulsatility index (PI)) in the central retinal artery. The hemodynamic flow parameters in these patients where compared to the levels of haemoglobin A1c, which was used as measure of long-term glycaemic control.
Generally, the mean central retinal artery hemodynamic flow parameters --peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistivity index-- did not differ significantly among diabetic patients with either normal (<7%), well-regulated (7-8%), or poorly regulated (>8%) glucose levels upon HbA1c measurement. However, the mean pulsatility index of the right retinal artery differed significantly among diabetics with varying degrees of glycaemic control (P < 0.05). Additionally, the duration which an individual has been diabetic was negatively correlated to the EDV in both the right (r = -0.201, n = 140, p = 0.017), and the left orbit (r = -0.181, n = 140, p = 0.033).
Our findings of no significant correlation between hemodynamic flow in the central retinal artery and HbA1c may indicate that the effects of glucose on ocular hemodynamic flow in DM are possibly short-lived and not long-term.