Research results published in a Journal of the Optical Society of America this month.
"It's been well established that high blood pressure can lead to a range of health problems, and many investigators feel that high blood pressure can contribute to the development of age-related eye disease," said co-author Alvin Eisner, Ph.D., senior scientist at the OHSU Neurological Sciences Institute. "Our results suggest that high blood pressure can lead to visual change even among people without eye disease. Among subjects with normal blood pressure, the ability of the eye to adjust to bright light appears to be related to blood pressure and heart rate, although probably not in a way that a person would be able to notice."
To conduct the research, scientists studied groups of middle-aged subjects (40 to 69 years old). Some of the subjects had previously been diagnosed with high blood pressure. Some of the subjects had no medical history of high blood pressure. All of the participants had to meet stringent criteria to be eligible for the study. For instance, eligible subjects were required to have 20/20 vision or better in the eye being studied and similar vision in the companion eye. In addition, subjects needed to have normal color vision, and they needed to have no history of eye disease, diabetes, ocular surgery or any of various other conditions, such as high eye-pressure or pronounced near-sightedness.
Both groups of subjects underwent a series of vision tests, some of which involved the use of a specialized device designed to control precisely how much light enters a subject's eye. Various aspects of visual sensitivity were evaluated, including, for instance, the ability of a subject to detect rapidly flickering light. Blood pressure and heart rate were measured. Most of the vision testing concerned visual function mediated by the portion of the retina called the fovea. The fovea, which lies in the retinal center, is the most sensitive part of the retina for many aspects of daytime vision, and it is the single most important region of the retina for fine visual tasks such as reading.
"What we found were several types of differences in the vision of those who have been diagnosed with high blood pressure and those who have not," explained study co-author John Samples, M.D., a physician at the Casey Eye Institute and professor of ophthalmology in the OHSU School of Medicine. "However, there was substantial overlap between the two research subject groups, and we have not proved that the high blood pressure condition itself led to the observed effects, but it seems likely."
Both researchers believe that future studies of age-related visual change should routinely include information regarding the blood pressure status of participating subjects. It is possible that some of the "normal" effects of aging on visual function involve changes in cardiovascular function that are not inherently part of the aging process. In any event, more work is needed to understand the relations between visual function and cardiovascular function.
In addition, both researchers feel their study adds one more item to a long list of reasons for Americans to take steps to avoid high blood pressure. What is good for a person's overall health is, in all likelihood, good for the eye.
The study was funded by The National Eye Institute, a component of the National Institutes of Health.