The optic nerves begin at the back of the eye in an area called the optic disc. They transmit visual information from the eye to the brain, which is responsible for comprehending the visual input. Many types of disorders can damage the optic nerves, including inherited diseases, acquired eye conditions, infections, inflammation, tumors and toxins. Damage to the optic nerves causes visual symptoms, which vary depending upon the underlying cause.
Loss of Peripheral Vision
The eyes normally function much like a wide-angle lens on a camera, taking in a broad view as opposed to seeing only what's straight ahead. The medical term for the breadth of what can be seen is called the visual field, which includes the central vision--that which is straight ahead--and the peripheral vision.
Damage to the optic nerves may cause loss of peripheral vision. Gradual loss of peripheral vision occurs with open-angle glaucoma, the National Eye Institute says. Tripping over unseen objects, not noticing objects to the side and difficulty driving often develop. "The Merck Manual for Healthcare Professionals" notes peripheral vision loss may also occur with optic neuritis, an inflammation of the optic nerve due to multiple sclerosis, infection, tumors or toxins. With significant loss of peripheral vision, perception is primarily in the central visual field. The view is much as it would be if you were looking through a tube. This is termed tunnel vision.
Loss of Central Vision
Optic nerve damage may cause loss of central vision. With this type of visual loss, there are blurry, dark or blind spots in the central visual field. The International Foundation for Optic Nerve Disease reports central visual loss occurs with Leber's hereditary optic neuropathy. This genetic disorder causes progressive central visual loss, which leads to blindness within approximately two months after the onset of symptoms. Visual symptoms typically begin between age 15 and 35, notes "The Merck Manual for Healthcare Professionals." Optic neuritis, lead and methanol poisoning, and certain medications may also cause loss of central vision.
Generalized Visual Loss
Some types of optic nerve damage cause a generalized visual loss affecting both the central and peripheral vision. Dominant optic atrophy, a hereditary eye disorder, causes slowly progressive, generalized loss of vision in both eyes. The University of Iowa Department of Ophthalmology and Visual Sciences says color blindness is common with this disorder. Ischemic optic neuropathy may cause sudden generalized loss of vision, advises "The Merck Manual for Healthcare Professionals." In this condition, the optic nerve is deprived of oxygen, causing damage and potentially the death of the nerve tissue.
