Arteriovenous (AV) nicking is a phenomenon seen in the eye, usually in association with hypertensive retinopathy. Patients with this condition experience retinal damage as a result of chronic high blood pressure. If it is not addressed, they could be at risk of vision loss and other serious complications, like cardiac problems caused by the sustained hypertension. An ophthalmological exam can show signs of AV nicking, also known as the Gunn sign, and pictures can be taken for the record or for evaluation by another health care professional.
In this clinical sign, at the point where one of the venules in the eye crosses an arteriole, the venule has a bulged, hourglass-like appearance. There are a number of theories to explain this phenomenon, including physical compression from the thickened walls of the artery and cellular changes that may occur with chronic high blood pressure. Whatever the cause, it can precede an occlusion, where the venule is partially blocked and cannot carry blood. This exposes the patient to the risk of serious complications.
Examination of the eye to identify AV nicking can be performed by introducing a bright light through the pupil to visualize the retina, and magnifying with the assistance of a lens. The eye may be dilated to make it easier to see as much of the retina as possible, and injectable dyes can be used to enhance contrast if the care provider thinks this may be helpful. Signs of AV nicking are usually very easy to spot, thanks to the distinctive bulges. Images can help care providers track changes in the eye over time, which may be important if they want to assess response to treatment.
When AV nicking develops, this indicates that ongoing damage is occurring and the patient needs to address the cause. High blood pressure is usually the culprit. Treatments can include diet and exercise modifications to determine if it is possible to lower blood pressure naturally. Medications are also available and may be recommended if the patient doesn’t respond to initial treatment. High blood pressure can increase the risk of not just retinopathy, but also glaucoma and damage to the optic nerve.
Patients with advanced hypertensive retinopathy typically have more signs in addition to the AV nicking. These can include cotton wool spots, areas of smeared vision across the eye, as well as blurred vision. Other clinical signs of high blood pressure may be present as well, like kidney damage and heart problems.