Lacunar strokes account for 25% of ischaemic strokes but its precise aetiology is unknown. Similarities between the retinal and cerebral small vessels mean that clarification of the exact relationship between retinal microvascular abnormalities and stroke, and particularly with stroke subtypes, may aid understanding of the aetiology of lacunar stroke and stroke risk.
We performed a systematic review of the literature by searching Medline and Embase to October 2007 for studies in humans that investigated the association between retinal microvascular abnormalities and prevalent or incident stroke. We extracted data and calculated summary risk ratios (sRR) for associations between retinal microvascular abnormalities and stroke, including stroke subtypes where possible, adjusted for key variables.
We included 37 papers from 21 different studies with 62,975 subjects (mean age 62 years) amongst whom there were 2,893 strokes. Stroke identification and diagnosis methods varied. Retinopathy was associated with incident stroke (sRR 2.1, 95% CI 1.7-2.6) and prevalent stroke (sRR 2.5, 95% CI 1.4-4.3). Incident stroke was also associated with retinal artery embolism (sRR 2.9, 95% CI 1.6-5.1) and venular widening (sRR 1.4, 95% CI 1.2-1.8). There was significant heterogeneity between studies for some associations. There were no data on retinal microvascular abnormalities and haemorrhagic versus ischaemic stroke or ischaemic stroke subtypes.
Retinal microvascular abnormalities are associated with stroke but more data are required to clarify associations between specific types of retinal microvascular abnormality and stroke, as well as between different stroke subtypes. Future retinal-stroke studies should concentrate on carefully diagnosing and accurately sub-typing ischaemic stroke.