Arteriovenous nicking, also known as AV nicking, is the phenomenon where, on
examination of the eye, a small artery (
arteriole
An arteriole is a small-diameter blood vessel in the microcirculation that extends and branches out from an artery and leads to capillaries.
Arterioles have muscular walls (usually only one to two layers of smooth muscle cells) and are the primar ...
) is seen crossing a small vein (
venule
A venule is a very small blood vessel in the microcirculation that allows blood to return from the capillary beds to drain into the larger blood vessels, the veins. Venules range from 7μm to 1mm in diameter. Veins contain approximately 70% of t ...
), which results in the compression of the vein with bulging on either side of the crossing. This is most commonly seen in eye disease caused by high blood pressure (
hypertensive retinopathy
Hypertensive retinopathy is damage to the retina and retinal circulation due to high blood pressure (i.e. hypertension).
Signs and symptoms
Most patients with hypertensive retinopathy have no symptoms. However, some may report decreased or blurred ...
).
It is thought that, since the arteriole and venule share a common sheath, the arteriole's thicker walls push against those of the venule forcing the venule to collapse. This makes the venule form an hourglass shape around the arteriole. Other theories suggest that this results not from compression from the arteriole but from
sclerotic thickening or
glial cell
Glia, also called glial cells (gliocytes) or neuroglia, are non-neuronal cells in the central nervous system (brain and spinal cord) and the peripheral nervous system that do not produce electrical impulses. They maintain homeostasis, form mye ...
proliferation at the site where the two vessels cross.
Signs
1. Gunns sign - Tapering of veins
2. Bonnet sign- Banking of veins
3. Salus sign - Deflection of veins
References
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Medical signs