Structural microvascular changes, visible in the eye, may precede development of severe hypertension

The eyes may be the window to the soul – and future hypertension, according to research reported in Hypertension: Journal of the American Heart Association.

The tiny vessels that supply blood to the retina appear to narrow before blood pressure exceeds normal ranges, said study co-author Paul Mitchell, M.D., Ph.D., professor of ophthalmology at the Center for Vision Research at the University of Sydney and Westmead Hospital, NSW, Australia. A long-term study suggests that people with relatively narrowed retinal arterioles (the tiny vessels of the retina) are twice as likely to develop severe hypertension in five years as people with relatively wider arterioles.

“These retinal signs appear to predict development of severe hypertension independent of other risk factors such as age, gender, body mass index, smoking, blood glucose levels, and blood pressure status at baseline,” Mitchell said. “This suggests that the risk associated with narrowed retinal arterioles adds to the risk associated with previous high blood pressure. For example, we already know that high normal blood pressure (pre-hypertension) or mild hypertension predicts later development of severe hypertension. At the same level of blood pressure, arteriolar narrowing signifies further risk.”

Mitchell and colleagues used special cameras to photograph the retinas of 3,654 Sydney residents who enrolled in the Blue Mountains Eye Study and to document retinal vessel wall structural changes. The participants, 82 percent of whom were 49 or older, were recruited to the study from 1992 to 1994.

Researchers also recorded the blood pressure of all participants and identified them as normal, high normal (systolic pressure 121–139 and/or diastolic pressure 81–89 mm Hg), mild hypertension (systolic 140–159 and/or diastolic 90–99 mm Hg) or severe hypertension (a previous diagnosis of hypertension and current use of antihypertensive medications, or systolic pressure 160 mm Hg or higher, or diastolic pressure 100 mm Hg or higher).

At baseline, 1,032 people had normal or high-normal blood pressure and 950 people had mild hypertension, said Mitchell. Researchers report that 1,319 of these 1,982 participants returned for follow-up examinations after five years. Among these, 390 (29.6 percent) had developed severe hypertension.

While the changes in retinal arterioles predicted hypertension regardless of age, “the association was even stronger in patients younger than age 65,” he said.

The study results confirm findings of another study, the Atherosclerosis Risk in Communities (ARIC) study. A study published earlier this year found that changes in the retina predicted new-onset hypertension within three years.

These findings suggest that structural microvascular changes, visible in the eye, may precede development of severe hypertension. Effective treatment for the earliest stages of hypertension might therefore need to target the microcirculation. These structural signs could also be a more stable measure of risk than functional measures, like blood pressure, which often vary over time.

The senior author is Wayne Smith, M.B., Ph.D., with co-authors Jie Jin Wang, M.Med., Ph.D.; Tien Yin Wong, M.B., Ph.D.; Elena Rochtchina, M.Stat.; Ronald Klein, M.D., M.P.H. and Stephen R. Leeder, M.B., Ph.D.