Retinal vasculature: a window on the brain.

1 studied 2907 participants in the Atherosclerosis Risk in Communities Study, who were free of diabetes mellitus, stroke, or coronary artery disease at baseline, and were followed for 13 years. Using retinal photographs and a simplified classification of hypertensive retinopathy, they found that even among patients who were well-controlled on antihypertensive medication, moderate/severe retinopathy carried a nearly 3-fold increase in the risk of stroke. Retinal signs of vascular pathology include an increased light reflex of the retinal arterioles (copper wiring or silver wiring, thought to occur as a result of atherosclerotic vessel wall thickening) and other arteriolar changes, including focal arteriolar narrowing, arteriovenous nicking, and microaneu-rysms. Retinal cotton-wool spots and exudates are the visible manifestations of small retinal infarctions and retinal hemorrhages , respectively, and represent the retinal consequences of the underlying arteriolar disease. All these findings predict an increased risk of vascular disease, and in particular, the risk of stroke, 2 but the kind of stroke predicted differs with the retinal findings as follows: copper wiring and silver wiring predict atherosclerotic cerebral infarction, 3 whereas signs of hypertensive arteriolar disease predict lacunar infarction 4 and probably also predict deep intracerebral hemorrhages because of hyaline degeneration or fibrinoid necrosis. 5 Although in the past most of the focus was on retinal arterioles, it is now apparent that retinal venous caliber is also important, particularly for risk of intracerebral hemorrhage. In the Rotterdam study, wider venular caliber was associated with lobar hemorrhage and anticoagulant-associated hemorrhage. Increasingly sophisticated methods for analyzing retinal vascular geometry have shown in recent years that the fractal geometry of retinal arteriolar branching differs by small vessel disease subtype, 6 increased complexity of retinal branching is associated with lacunar infarction, and age-related rarefaction of retinal arteri-oles with deep white matter intensities on MRI. The classification by Ong et al 1 of retinopathy into none, mild, moderate, or severe is a simplified approach compared with historical classifications, such as the Keith–Wagener classification, but is helpful to clinicians. Also helpful was their pointing out that retinal photographs are readily available , even in optical shops in the community, and therefore, assessment of retinopathy is available even to clinicians not skilled in ophthalmoscopy. One diagnostic trap is worth mentioning: as discussed by Matas, 7 simple obscuration of the venular wall behind a thickened retinal arteriole is a result of atherosclerotic wall thickening and should not be mistaken for arteriovenous nicking. In …