Background: Lacunar strokes account for 25% of ischaemic strokes, but their 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. Methods: A systematic review of the literature was performed 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. Data and calculated summary risk ratios (sRR) were extracted for associations between retinal microvascular abnormalities and stroke, including stroke subtypes where possible, adjusted for key variables. 37 papers from 22 different studies were included with 62 975 subjects (mean age 62 years) among whom there were 2893 strokes. Stroke identification and diagnosis methods varied. Results: Retinopathy was associated with incident stroke (sRR 2.1, 95% CI 1.7 to 2.6) and prevalent stroke (sRR 2.5, 95% CI 1.4 to 4.3). Incident stroke was also associated with retinal artery embolism (sRR 2.9, 95% CI 1.6 to 5.1) and venular widening (sRR 1.4, 95% CI 1.1 to 1.7). 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. Conclusions: 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.Lacunar ischaemic stroke accounts for 25% of all ischaemic strokes, 1 but its precise aetiology is unknown.2 Possible causes include atherothromboembolism, 3 intracranial large artery stenosis, intrinsic microvascular atheroma, or endothelial dysfunction manifesting either through ischaemia or failure of the blood-brain barrier. 4 The cerebral blood vessels that, when diseased, give rise to lacunar stroke share many characteristics with retinal vessels, 5 being developmentally related during embryogenesis and of similar diameter (50-250 mm). Retinal vessels are visibly affected by known risk factors for stroke such as diabetes and hypertension.6 Therefore, determining any association between retinal microvascular abnormalities and stroke may improve understanding of the nature of the cerebral small vessel changes underlying lacunar ischaemic stroke and aid cerebrovascular and cardiovascular risk profiling.Several studies have examined a possible link between stroke and the retina, including large epidemiological studies in community-dwelling populations and small detailed studies of patients with specific diseases attending tertiary hospitals. The presence and strength of any repo...

Retinal venules are wider and arteriovenous ratios are smaller in patients with lacunar strokes compared with those in patients with cortical strokes.