Retinal microvascular signs are frequently seen in people with hypertension, a condition sometimes referred to as hypertensive retinopathy, the authors point out. It is unclear, however, when these small vessel wall changes develop in the course of hypertension, and, if they precede it, whether they may signal systemic pathology, they note.

A paper published earlier this year from the Atherosclerosis Risk in Communities (ARIC) study provided some evidence on this question, showing subjects with generalized or focal retinal alveolar narrowing were 60% more likely to develop hypertension within three years than those without these changes.2

For this report, the researchers used data from the Blue Mountains Eye Study, a population-based cohort study of vision, eye diseases, and other outcomes in a group of 3654 residents of two postal code areas west of Sydney, who were 49 years or older at baseline. Each had retinal photographs taken at that time.

This report focused on 1319 subjects who both returned for the five-year follow up examination and were free of severe hypertension at baseline. At the study outset, each was classified as normotensive, high-normal (prehypertensive), or mildly hypertensive, defined as 140 to 159 mm Hg systolic and/or 90 to 99 mm Hg diastolic.

Of these, 390 (29.6%) had developed severe hypertension (systolic BP >160 mm Hg or diastolic BP >100 mm Hg) by the five-year examination. After adjusting for age, sex, body mass index, smoking, glucose, and total cholesterol, generalized retinal arteriolar narrowing was associated with a more than doubling of risk for incident severe hypertension, comparing the quintiles with the narrowest vs the widest vessels (odds ratio 2.6, 95% CI 1.7-3.9).

The association remained significant after further adjustment for baseline mean arterial BP or BP status, they note. The risk was more apparent in younger than older subjects.

Wang and Mitchell told heartwire that problems with precision and instrumentation in measuring the caliber of small vessels mean their findings probably don't have immediate clinical application in predicting risk among patients seen in clinical practice. "Development of automated methods to quantify retinal vessel wall signs in vivothis is potentially achievablemay substantially improve their clinical applicability," they note. In the meantime, though, certain antihypertensive medications, such as ACE inhibitors, target the microcirculation "and thus could have therapeutic effects beyond reduction in blood pressure. This will be a potentially important area for future research."