Sir,

I read with interest the case–control study by Gonen et al1 who sought to identify the incidence of renal artery stenosis (RAS) and abdominal aortic aneurysm (AAA) in patients with pseudoexfoliation syndrome (PXE).

PXE affects 30% of patients over 60 years of age;1 not all can undergo ultrasonographic screening. Elucidating the quantitative contribution—or relative risk—of PXE to cardiovascular disease is critical in identifying patients at significant cardiovascular risk who can be referred from ophthalmic clinics for further management. Any study seeking to evaluate the significance of a candidate cardiovascular risk factor must therefore identify and control all other established cardiovascular risk factors (Table 1).

Table 1 Cardiovascular risk factors
Full size table

Gonen et al1 did not account for serum cholesterol and urinary albumin excretion—two major independent cardiovascular risk factors associated with AAA and RAS—which may have conceivably contributed to their development. These were not obviously examined as explicit parameters, nor proven statistically equivalent between PEX cases and controls.

Hypercholesterolaemia has been demonstrated as an independent risk factor for both RAS and AAA. Overall, 33% of patients with heterozygous familial hypercholesterolaemia have RAS on formal renal angiography, predominantly proximal in location.2 Meta-analysis of pooled data from eight studies identified significantly lower HDL and higher LDL cholesterol in patients with AAA compared to controls.3

Microalbuminuria (>30 mg/24 h) is an independent cardiovascular risk factor and predictive of all-cause cardiovascular mortality (relative risk of 3.2).4 Microalbuminuria is associated with increased renovascular resistance and reduced aortic compliance in diabetic subjects, after adjustment for other cardiovascular risk factors.5 Microalbuminuria may conceivably influence renal artery peak systolic velocity parameters used as an end point in this study.

A prospective longitudinal cohort study is required in patients with PXE to determine the relative risk of serious cardiovascular events in relation to other risk factors. Alternatively, ocular examination of subjects in large existing population-based studies such as the Framingham Heart Study may help to identify the contribution of PXE to cardiovascular risk.

Urinary albumin estimation and serum cholesterol assays may have added further value to this study by excluding potentially confounding variables on the expressions of cardiovascular disease in PXE.