By Anthony Ekong, MD, Illinois Retina & Eye Associates
Systemic arterial high blood pressure or high blood pressure (HBP) has widespread and profound effects on our eyes. Unlike the other organs affected by high blood pressure, the eye is unique in that it allows for the effect of elevated blood pressure to be observed early, through changes in the blood vessels of the retina.
Even people on medication with good control of their blood pressure may still have damage to their retinal blood vessels or hypertensive retinopathy. Retinopathy is the most common manifestation of HBP and refers to damage to the retinal blood vessels due to acute and/or chronic (long-term) elevations in blood pressure.
Here we focus on changes seen in people with chronic HBP.
Eye Findings in Long-Term High Blood Pressure
In general, HBP increases the blood flow to a tissue, which the small blood vessels usually cannot handle, and are thus eventually damaged.
Fortunately, the retinal blood vessels, the arterioles, like those present in the brain, have a built-in protective blood flow regulating mechanism called autoregulation that enables it by constricting or dilating to maintain constant blood flow despite changes in blood pressure. It’s this autoregulation response or its breakdown when the BP rises above a certain range, which is responsible for some of the eye changes seen in people with high blood pressure.
The initial response of the retinal blood vessels, the arterioles to HBP is vasoconstriction or narrowing to control the amount of blood that is delivered to the retina. There are two types of narrowing of the arterioles that occur with persistent hypertension; generalized arteriolar narrowing in which the whole arteriole is diffusely narrowed, or focal narrowing in which the arteriole has a constricted area. Arteriolar narrowing could also result from arteriosclerosis in the absence of hypertension.
If the HBP is not treated and remains chronically high, other changes occur in the retinal blood vessels. The arterioles respond by thickening or hardening its walls to enable it to handle the increased pressure. Over time, HBP-related changes can limit the amount of blood that can flow through the blood vessels.
In the retina, the arteriole and vein share a common covering and usually cross over each other. In people with HBP, this normal crossing is complicated by the thick and stiff arteriole’s walls pushing against the veins, which results in the compression of the veins with bulging on the crossing. This sign of damage to the retina by hypertension is called arteriovenous nicking and can contribute to blockage of veins with serious visual consequences.
Patients with the changes described above are said to have mild hypertensive retinopathy, usually suggestive of chronic hypertensive damage. Thus they are related not only to the patient’s current blood pressure levels, but also to previous high blood pressure.
These retinal arteriolar changes may in some cases enable the eye care professional to make the initial diagnosis of hypertension and refer the patient for treatment. It’s not always the case that hypertensive retinopathy is present when these retinal signs exist, but the index of suspicion should be heightened if these features are present.
Dr. Ekong is a fellowship-trained retina specialist at Illinois Retina & Eye Associates in Peoria and helps individuals achieve better vision through advanced treatments for macular degeneration, diabetic eye disease, and other retina diseases. Attend a presentation by Dr. Ekong and Dr. Michael Grossman, comprehensive ophthalmologist, “I’m Getting a Little Older, Why Can’t I See As Well?” Oct. 28 or Nov. 6. Macular degeneration and cataracts will be discussed, with a video of a LIVE cataract surgery shown. For more information, please call 309-589-1880 or visit www.illinoisretinainstitute.com.