Optic neuritis is something that can happen in either children or adults; it may also involve one or both of a person's optic nerves.
Defining Optic Neuritis
Optic neuritis is inflammation of a person's optic nerve. The optic nerve is the structure that connects a person's eye to their brain. The optic nerve is comprised of axons which originate in the retina of each eye. The optic nerve carries visual information from the person's retina to the nerve cells in the person's brain stem where the information is then relay/health/autoimmunediseases/Information regarding autoimmune diseased to the area of the person's brain that recognizes vision, referred to as the, 'occipital cortex.'
Optic neuritis is something that can happen in either children or adults; it may also involve one or both of a person's optic nerves. Optic neuritis commonly affects young adults between the ages of eighteen and forty-five years of age. The average age of people affected by optic neuritis is between thirty and thirty-five. More females are affected than males. Approximately five out of every one-hundred thousand people are affected by optic neuritis each year.
Causes of Optic Neuritis
The exact cause of optic neuritis remains unknown at this time. Medical science believes it may be a form of autoimmune disorder. A person's immune system generally fights infections through creation of a reaction that fights viruses, bacteria, fungi, and additional foreign proteins. Where autoimmune diseases are concerned; however, this reaction on the part of a person's immune system is mistakenly directed against a part of the person's body, causing inflammation and potentially, damage. Where optic neuritis is concerned, the person's optic nerve becomes inflamed and its function impaired. The inflammation causes the person to experience a loss of vision due to the swelling and destruction of the protective myelin sheath that both covers and insulates their optic nerve. Damage to the person's axons can also occur, resulting in nerve destruction.
For some people, the signs and symptoms of optic neuritis might be an indication of multiple sclerosis, a disease involving immune system attacks on the person's myelin sheath covering nerve fibers in their brain and spinal cord, which results in inflammation and damage to the person's nerve cells in their spinal cord and brain. Another term for this condition is, 'demyelinating optic neuritis.' People affected by optic neuritis resulting from demyelinating disease, multiple sclerosis in particular, might experience recurrences of optic neuritis over time.
Among people who eventually develop multiple sclerosis, between fifteen and twenty-percent experience optic neuritis as a first symptom. The risk of developing multiple sclerosis after a single episode of optic neuritis is around fifty-percent within fifteen years of the episode of optic neuritis. After receiving an MRI scan, nearly half of the people with optic neuritis present with abnormal brain white matter changes that were consistent with multiple sclerosis. In people who received MRI scans as they were experiencing an initial attack of optic neuritis, the finding of brain lesions on MRI images increased the risk of development of later multiple sclerosis by three times over people with average MRI scan results. Nearly have of people with any brain lesions on MRI results at the time of their initial episode of optic neuritis have not developed multiple sclerosis even ten years later.
One other autoimmune condition that causes optic neuritis is, 'neuromyelitis optica.' The condition is considered to be unusual and causes inflammation in the person's optic nerve and spinal cord, although not usually within the person's brain as often as multiple sclerosis. Optic neuritis resulting from neuromyelitis optics is often more severe than the optic neuritis people experience in association with multiple sclerosis. There are a number of causes of optic neuritis that are not associated with multiple sclerosis. Among these causes are the following.
Autoimmune Diseases: Autoimmune diseases, such as systemic lupus, might cause inflammation of blood vessels that nourish the optic nerve.
Cranial Arteritis: Cranial arteritis involves an inflammation of the lining of the arteries within the skull. Inflammation of cranial arteries may block the flow of blood to a person's eyes and brain, leading to permanent vision loss or stroke. Cranial arteritis is also known as GCA.
Diabetes: Diabetes is a condition in which a person's body is unable to make or appropriately use insulin, a hormone that regulates the amount of sugar in the blood and additional tissues. People with diabetes are at an increased risk of developing disorders of their optic nerve, to include optic neuritis.
Drugs: Some drugs have been associated with the development of optic neuritis, to include ethambutol and some antibiotics.
Infections: Bacterial infections, such as tuberculosis, Lyme disease, toxoplasmosis, cat scratch fever, and syphilis, as well as viral infections to include hepatitis B, HIV, and herpes zoster, may cause optic neuritis. Encephalitis, bacterial meningitis, and sinusitis can cause optic neuritis as well.
Lebers Hereditary Optic Neuropathy: Leber's hereditary optic neuropathy is an inherited form of vision loss that affects largely males in their twenties and thirties and can cause optic neuritis.
Radiation Therapy: Radiation therapy administered to a person's head is an uncommon cause of optic neuritis.
Sarcoidosis: As well as pernicious anemia, Graves disease, bee stings, and vaccinations, mall all cause vision loss from swelling of the person's optic nerve.
Toxins: Methy alcohol, lead, arsenic, and quinine can cause vision loss and additional symptoms which mimic optic neuritis.
The term, 'optic neuropathy,' is one that is used to describe any condition that results in damage to a person's optic nerve. Optic neuritis itself is a particular type of optic neuropathy that is the result of inflammation. Some of the common, noninflammatory causes of optic neuropathy include:
Blocked or limited blood flow
Elevated intracranial pressure
Direct trauma to the optic nerve
Primary and metastatic optic nerve tumors
Trauma may interfere with the nerve's ability to conduct electrical impulses. Any of these can cause a person to experience a loss of vision, as well as additional symptoms that mimic optic neuritis.
Symptoms of Optic Neuritis
The most characteristic signs a doctor finds after examining someone includes a reduction in their visual accuracy, a measurable change in their peripheral vision, a decrease in their perception of brightness in the eye that is affected, as well as a change in the person's color vision - something that is often out of proportion to their loss of visual acuity. There is also a detectable disturbance in the function of the person's pupil if the person's other eye is either unaffected or is involved but to a lesser degree.
The main symptom of optic neuritis is loss of vision, something that occurs within one or two days and varies from a small area of blurring to complete blindness. People who are affected by optic neuritis might also experience a distorted vision, loss of contrasts, reduced color vision, and vision that is, 'washed out,' or less vivid than usual. The loss of vision commonly develops over the course of a day or two, but may take up to two week, and could be worsened by exercise or heat. The loss of vision is usually temporary, although it may be permanent in some cases.
The majority of people who develop optic neuritis experience eye pain that is made worse when they move their eyes. The pain that is associated with optic neuritis commonly peaks within a week, then disappears within several days. Optic neuritis usually affects only one of a person's eyes, although it can affect both of a person's eyes at the same time. At times when only one of a person's eyes is affected, people might be unaware of subtle visual loss or changes in their color vision until a doctor asks them to close or cover their healthy eye.
Diagnosing Optic Neuritis
Optic neuritis is something a doctor suspects as a diagnosis in people who experience characteristic eye pain and vision loss. A doctor will pursue a complete medical examination, to include chemical analysis of the person's blood, with the goal of ruling out any related diseases. The tests might include pupillary testing, visual acuity testing, color vision testing, visual field testing, and visualization of the person's optic disc either directly or indirectly through opthalmoscopy.
People experiencing their first episode of optic neuritis commonly undergo an MRI of their brain to look for central nervous system lesions. An MRI exam with gadolinium enhancement might reveal an enlarged, enhancing optic nerve. An MRI can also assist in diagnosing multiple sclerosis by revealing typical abnormalities in the person's brain.
Treatment of Optic Neuritis
Should a doctor find a definite cause, such as a disease or an infection, they can treat the disease or infection. If the person's optic neuritis is due to something that cannot be determined, or is related to multiple sclerosis, the person's vision many times returns to usual within two to twelve weeks without treatment, although it could also advance to a permanent state of either partial or total loss of vision.
Treatment with steroid medications such as Deltason, Orason, Prednison, Methylprednisolone or others can speed up the persons vision recovery time. While treatment with steroids have little effect on the end visual outcome of people with optic neuritis, people who receive initial treatment with intravenous steroids have around half of the risk of developing multiple sclerosis in two years compared with people who do not receive such treatment. The affect disappears by the third year of follow up. People who receive intravenous steroid treatment experience fewer repeated attacks of optic neuritis than people who do not. Intravenous steroid treatment is commonly followed by approximately eleven days of oral steroids. When optic neuritis is associated with MRI lesions which are suggestive of multiple sclerosis, immunosuppressive or immunomodulator therapy might be prescribed with the goal of reducing the number of future attacks.