We read with interest the report of the Barbados Eye Study1 in which Leske and associates reportedly failed to identify blood pressure (BP) as a "risk factor" for primary open-angle glaucoma (POAG). While there were many differences between their study and the Baltimore Eye Survey (which included 2500 African-Americans aged 40 years and older), the Baltimore study was able to identify a complex, biologically plausible relationship between BP and the risk of POAG.2
As we had anticipated, two interesting results came from our analyses. There was moderate evidence to suggest that elevated BP was protective at younger ages, presumably before significant vascular narrowing had occurred. Elevated BP was deleterious in the older age group, perhaps because vascular stenosis from chronic hypertension had reduced perfusion despite an elevated pressure head. There was also a marked relationship between perfusion pressure (BP minus intraocular pressure[IOP]) and the risk of POAG that