Retinal vessel calibres and haemostasis in black and white South Africans: the SABPA study

Retinal arteriolar narrowing associates with hypertension development and indicates increased cardiovascular risk. Evidence on whether the retinal vessel calibres are related to the haemostatic system is limited, especially in the black hypertension-prone population with a high stroke incidence. We therefore investigated the relationships between haemostatic markers and retinal vessel calibres.

We performed a cross-sectional study involving 170 black (mean age, 58 years; 44% women) and 189 white (mean age, 49 years; 52% women) teachers, and determined ambulatory blood pressure, haemostatic factors (fibrinogen, von Willebrand factor, D-dimer, plasminogen activator inhibitor-1 and clot lysis time) and retinal vessel calibres (central retinal artery and vein equivalent). The black and white groups were stratified by median split of the retinal arteriolar calibre.

Both ethnic groups with a smaller arteriolar calibre had higher SBP and narrower venular calibres. In the black population, the central retinal vein equivalent was positively (β = 0.293; P = 0.024) associated with fibrinogen, whereas in the white population, the central retinal artery equivalent (β = -0.256; P = 0.016) was negatively and central retinal vein equivalent (β = 0.234; P = 0.021) positively associated with von Willebrand factor. Furthermore, clot lysis time was negatively associated with the central retinal artery equivalent (β = -0.390; P = 0.014) in the black group and positively associated with the central retinal vein equivalent (β = 0.275; P = 0.008) in the white group.

Relationships between markers of haemostasis and the retinal vessel calibres exist, and vary between ethnicities. Haemostatic alterations are linked to early retinal microvascular changes, and future studies should investigate whether it translates into an elevated stroke risk.