The optic nerve is located at the back of the eye and is responsible for sending information from the retina to the brain. Essentially, it allows the brain to process what the eye is seeing. The optic nerve and the retina are two of the most important parts of the eye so damage to either of these is definitely cause for concern. This article aims to provide an overview of what causes optic nerve damage, any complications that may arise with nerve damage and some possible treatment options.
What Is Optic Neuritis?
The medical term for optic nerve damage is “Optic Neuritis” (ON) and this refers to inflammation of the optic nerve. The inflammation within the nerve is typically due to damage of the protective shield around the optic nerve called “myelin”. As nerve tracts are the communication route to the brain, it is no surprise that when this pathway is damaged vision will be affected.
The most common symptoms of ON are a loss of vision, usually only in one eye, which can last up to 10 days, pain around the eye especially when moving the eye, as well as the inability to see colors correctly. Those affected by ON may also experience distorted vision and that colors are washed out or not as bright as they typically would be.
Those suffering with ON may also find their symptoms worsened by the heat in a phenomenon known as Uhthoff's phenomenon. While in most cases these changes to vision are temporary, in some cases they may be permanent.
What Causes Optic Neuritis?
The specific cause of ON is unknown thus meaning there is not really one particular cause. The most common cause of ON is thought to be linked to Autoimmune diseases. The body’s first line of defence against infection and viruses is through the immune system which works to protect the body and keep it healthy. With Autoimmune diseases the immune system does not function normally and will mistakenly begin to attack normal parts of the body as if they were infections or viruses.
When ON is developed as a direct impact of an Autoimmune disease what happens is the optic nerve becomes swollen and inflamed after being attacked by the immune system. Unsurprisingly, being swollen and inflamed impairs the nerves ability to transmit images effectively from the retina to the brain which then, in-turn, effects the over quality of vision.
While autoimmune disease is thought to be the most common cause of ON, there are a number of factors that can cause Optic Neuritis. These factors are typically linked to nerve diseases or infections, let's look at a couple in a little more detail.
There are a number of infections that can increase the chances of getting ON but the chances of developing ON as a direct result of these illnesses is rare. The reason ON may develop as a complication of other illnesses could be due to a weak immune system and not treating the initial illness or infection properly. Infections that may lead to ON developing as a complication include bacterial infections and viruses like Lyme disease, syphilis, measles, mumps, herpes, shingles, meningitis and tuberculosis.
Multiple Sclerosis (MS)
Multiple Sclerosis is an autoimmune disease in which the immune system of the body starts to attack healthy cells. MS can cause the immune system to attack the protective myelin of the optic nerve and when this happens it reduces the speed at which images reach the brain. This can distort vision and how images are sent to the brain as well as affecting the eyes ability to see at all.
It is a common symptom of MS to develop vision loss with up to 50% of patients reporting problems with their vision. So a diagnosis of MS vastly increases the likelihood of developing optic nerve damage. A diagnosis of ON can also be a warning sign of MS with 15-20% of people eventually developing MS with ON being their first symptom.
Less Common Causes Of ON
There are a number of other reasons that may cause ON to develop including rare autoimmune diseases like Guillain-Barre syndrome, rare responses to vaccinations and some chemicals and drugs like quinine and certain antibiotics.
Risk Factors – Who Is More At Risk To Develop On?
There are certain factors that may increase someone’s likelihood of developing ON. Some of these include specific trauma to the eye, pre-existing nutritional problems, diabetes or glaucoma. Some studies have shown that there are some other factors that can affect your likelihood of developing ON, these include the following:
- Age: Your age can directly impact your likelihood of developing ON. Those most likely to develop ON are typically between the ages of 18 to 45.
- Sex: Women are more likely than men to develop ON.
- Race: Statistics show that ON is more common in people with lighter skin than those with darker skin.
- Genetic Mutations or Inherited Genes: If there is a history of genetic mutation in your family for example the HLA DR(2)15 genetic mutation, there is a higher risk of developing illnesses like MS that can cause ON.
- Other weak risk factors include living at a higher altitude, particularly during your childhood, being exposed to infectious diseases like Lyme disease and syphilis as well as having an EBV infection during late childhood.
There are a number of complications that may arise as a result of having ON however they are usually not critical or life threatening.
Decreased Visual Activity
For those who have had ON typically they will recover normal vision or very close to normal vision within a few months of finishing their treatment. However, in some cases where normal vision is not regained, patients may suffer with a partial loss of the ability to clearly distinguish between different colors.
Side Effects Of ON Treatment
Complications may arise during, or as a result of, the treatment of ON. The typical treatment for ON is a steroid medication that works to moderate the immune system. The effect of having a less effective immune system can leave you at a higher risk to develop other infections as your body will be less effective at fighting off infection. Side effects of the steroid treatment for ON can also include mood swings and mood changes as well as potential weight gain, upset stomach and insomnia.
Treatment For Optic Neuritis?
In most cases ON can improve on its own without the need for intervention or serious treatment – treatment will typically only be advised when a definite cause is identified. When the specific cause of ON is identified within a patient and medical treatment is considered necessary, a steroid treatment will be given. This is administered intravenously (by vein) and may increase the recovery time but does not directly affect the amount of vision or the quality of vision that will be recovered.
This steroid treatment does not only work to help to treat ON, it is usually also administered in an attempt to slow the development of Multiple Sclerosis. As mentioned previously, if someone has developed ON it is likely that they will develop MS in the future, particularly if the case of ON is recurring.
If the steroid treatment fails to work effectively to restore the vision loss, there is an alternative treatment that may be offered. A treatment called “Plasma Exchange Therapy” may be given in an attempt to aid in vision recovery. However, there is limited evidence to prove that this form of therapy is effective and works to help patients of ON.
Other medication that may be prescribed to those suffering with ON include non-steroidal anti-inflammatory medication. While there is no evidence that these medications works to improve the quality of a patient's vision, they may work to ease any pain that may be caused as a result of ON. Particularly pain when moving the eye which is a common symptom of ON.
There are also a number of lifestyle changes that can be taken into account in an attempt ease the symptoms during acute optic neuritis. These include avoiding overheating to prevent Uhthoff's phenomenon from worsening symptoms, as well as avoiding smoking, keeping hydrated and maintaining a healthy balanced diet with plenty of fruit and vegetables.
Optic Neuritis Prognosis
Like many medical issues the prognosis of ON depend mainly on the underlying cause. The majority of cases will clear up without medical intervention within a time span anywhere between two weeks to three months. However, the minority of cases can experience recurring ON and with recurring cases there is also the increased risk of ON developing into both eyes within 10 years. Those that experience recurring ON are also at higher risk of developing Multiple Sclerosis within 15 years of diagnosis.