This is the main artery that supplies blood to the eye, specifically the retina. The artery travels inside the optic nerve. Once the artery enters the back of the eye at the optic disk, it branches widely within the superficial layers of the retina. These coursing blood vessels can be examined during a dilated eye exam. This is the only artery in the body that is visible to the naked eye (i.e., not obscured by opaque skin). Some medical problems, like hypertension, can be detected by looking at this artery during an eye exam.