The optic nerve is your eye's connection to the brain and is critical to how you process sight. If the optic nerve becomes swollen, vision can be dramatically affected. While swollen optic nerves can have many causes, the most common ones include papilledema or increased spinal fluid pressure, inflammation, blood vessel blockage, infection and a mass compressing the nerve.
Papilledema describes optic nerve swelling due to increased intracranial pressure, which means the pressure inside your skull is abnormally elevated. It can be caused by a tumor, a disorder in the absorption of spinal fluid by the body or benign idiopathic intracranial hypertension. Idiopathic intracranial hypertension means there is no tumor or other disorder, but the intracranial pressure is still high. It is most commonly seen in women of childbearing age who are markedly overweight. Primary symptoms of papilledema include headaches, blurry vision, nausea, pulsating sounds in the ears and dizziness.
Optic nerve swelling due to inflammation is called optic neuritis. Optic neuritis may be the first sign of an autoimmune disease, such as multiple sclerosis. It can also be caused by certain infections, including measles, mumps, chicken pox, shingles, Lyme disease, cat scratch fever, meningitis and syphilis. Generally, optic neuritis presents in one eye only and can cause blurry vision or loss of vision associated with eye pain.
Ischemic Optic Neuropathy
Ischemic optic neuropathy is a swollen optic nerve caused by damage to one of the arteries leading to the eye. In younger individuals, this condition typically starts with a painless loss of vision in one eye caused by a blocked artery. In people older than 65, it is usually due to inflammation of a branch of the carotid artery near the temple, which presents with painful vision loss in one eye. Pain is often worse when chewing food or brushing the hair. High blood pressure, high cholesterol and diabetes increase the risk for ischemic optic neuropathy.
Another cause of optic nerve swelling could be a mass or tumor that presses on the optic nerve. This could be in the brain, pituitary gland, retina or other structures near the eye. An overactive thyroid gland may also lead to compression of the optic nerve. Symptoms include headaches, an eye that bulges from the socket or inability to move eyes smoothly in all directions.
Because optic nerve swelling can have many causes and many are related to serious health conditions or infections, it is important to see an eye care professional immediately if you have eye pain or loss of vision.