The optic nerve enables people to see by translating photons of light into electrical impulses that can be interpreted by the brain. The optic nerve is the second of 12 cranial nerves that exit the brain through holes, called foramen, in the skull. When the optic nerve is damaged by disease or injury, blindness can result.
Optic Gliomas
Optic gliomas are slow growing, mostly benign tumors that grow in the optic nerves. The National Institutes of Health reports that they are most commonly found in people younger than age 20. A person with an optic glioma may experience symptoms such as bulging eyes, uncontrollable eye movement and the tendency to squint.
Doctors don't know the causes of optic gliomas, but use treatments such as surgery, radiation and therapy to treat them.
Neuromyelitis Optica
Neuropmyelitis optica is a disease in which the myelin sheath, a protective fatty layer that covers the nerve, becomes inflamed and damaged. Its cause is unknown. The disease affects the optic nerve and spinal column. MayoClinic.com describes neuromyelitis optica as more severe than multiple sclerosis, another disease that can cause demyelination of the optic nerve.
Ocular Toxoplasmosis
Toxoplasma gondii is a parasite that is found in animal feces, undercooked meat and drinking water, states the Jules Stein Eye Institute and the Department of Ophthalmology at UCLA. This parasite has been noted as a concern for pregnant women, who can be infected by contaminants in, among other things, cat litter boxes. Toxoplasmosis can affect the eye, a condition known as ocular toxoplasmosis. This disease manifests as reduced or blurred vision, eye pain and redness, and tearing of the eye. Ophthalmologists can treat the disease with medications.
Glaucoma
Many cases of blindness in the United States are caused by glaucoma. Dr. Gary Heiting, editor of the journal "Refractive Surgery News," states that nearly 2.5 million Americans suffer from the disease. In glaucoma, fluids build up in the eye, putting pressure on the optic nerve. This pressure if unabated can damage the nerve. Peripheral vision loss is often the first symptom of glaucoma, and by the time that symptom occurs the nerve has already been damaged beyond repair. An eye doctor can detect the disease before any symptoms have been observed by using a device called a tonometer to measure the pressure in the eye. Glaucoma is treated with eye drops or surgery. If left untreated, the vision loss can get progressively worse, until complete blindness results.
