Exophthalmos is a medical term for a bulging or protruding eyeball or eyeballs.
It is often used interchangeably with the term "proptosis", which means the same thing.
What causes exophthalmos?
Exophthalmos can be caused by many different conditions. It's important that the underlying cause is identified so appropriate treatment can be given.
Thyroid eye disease
One of the main causes of exophthalmos in the UK is thyroid eye disease, also known as Graves' ophthalmopathy.
This is an autoimmune condition that affects around one in every three people with an overactive thyroid gland (hyperthyroidism) caused by Graves' disease. It is particularly common in women who are 30-50 years of age and people who smoke.
An autoimmune condition is where the immune system (the body's defence against illness and infection) mistakenly attacks healthy tissue.
In the case of thyroid eye disease, the immune system attacks the muscles and fatty tissues around and behind the eye, causing them to become inflamed (swollen).
Graves' disease is an autoimmune condition in which the thyroid is attacked, leading to an increase in the level of thyroid hormones in your blood. It's not clear exactly why thyroid eye disease sometimes occurs along with this condition.
Thyroid eye disease can also occasionally affect people with an underactive thyroid gland (hypothyroidism) and, in rare cases, people with seemingly normal thyroid function.
Exophthalmos can also have a number of other causes, but these are generally less common than thyroid eye disease.
Other cause of exophthalmos can include:
an injury to the eyes
bleeding behind the eyes
abnormally shaped blood vessels behind the eyes
an infection of the tissue in the eye socket
cancerous tumours – such as those caused by neuroblastoma and some soft tissue sarcomas
Exophthalmos can also affect newborn babies if they are born with eye sockets that are shallower than normal.
Other problems associated with exophthalmos
Depending on what is causing your bulging eyes, you may also have other associated symptoms. For example, if exophthalmos is caused by a thyroid eye disease, your eyes may also be:
inflamed, red and painful
dry and "gritty"
sensitive to light (photophobia)
You may also experience some double vision.
In severe cases of exophthalmos, you may not be able to close your eyes properly. This can damage your corneas (the transparent tissue that covers the front of your eye) by causing them to dry out.
If your corneas become very dry, an infection or ulcers (open sores) may develop. These could damage your vision if left untreated.
There is also a small risk of the optic nerve (which transmits signals from the eye to the brain) becoming compressed if you have exophthalmos, which may affect your sight permanently if it is not treated quickly.
Seeking medical advice
It's important to see your GP or an optometrist (optician) if you notice that one or both of your eyes are protruding, as treatment is often more effective if it's started as soon as possible.
If necessary, your GP or optometrist can refer you to an ophthalmologist (a specialist in diagnosing and treating eye conditions) for further assessment.
The ophthalmologist will check how well you are able to move your eyes. They may also use an instrument called an exophthalmometer to measure how far your eyeball protrudes.
If the ophthalmologist wants to examine your eye socket in more detail, a computerised tomography (CT) scan or magnetic resonance imaging (MRI) scan may be carried out.
You may also have a blood test to assess how well your thyroid gland is working, and you may be referred for an assessment by an endocrinologist (a specialist in conditions affecting glands and hormones) if you are found to have abnormal thyroid hormone levels.
If exophthalmos is being caused by thyroid eye disease, the following treatments are often helpful:
medication to correct the level of thyroid hormones in your blood – this will not necessarily improve the problems with your eyes, but may stop them getting worse
corticosteroid medication given directly into a vein (intravenously) – this can help reduce the inflammation associated with the condition
corrective surgery – this may be carried out to improve the appearance of your eyes once the inflammation is under control
Other useful measures include stopping smoking, using artificial tears to reduce eye dryness and irritation, and wearing special lenses to correct double vision.
In other cases, treatment will vary depending on the underlying cause of the condition. For example, treatments such as radiotherapy,chemotherapy and/or surgery may be recommended if exophthalmos is caused by a tumour.
The outlook for exophthalmos can vary considerably.
Many of the symptoms of thyroid eye disease tend to improve over time, although this can take a number of years, and there is a chance your eyes will continue to protrude if corrective surgery is not carried out.
Some people with exophthalmos are left with long-term vision problems, such as double vision, but permanent visual impairment is rare if the condition is identified and treated promptly.
Treatment for exophthalmos (bulging eyes), will largely depend on what is causing the problem.
In some cases, an ophthalmologist (eye specialist) may feel that immediate treatment is not necessary, in which case you may be advised to have regular examinations to monitor your condition.
Treating thyroid eye disease
If you have thyroid eye disease, your treatment may involve several different stages. This is because the condition tends to progress through two main phases:
an "active" phase – when symptoms caused by inflammation of the eyes, such as dryness and redness, are prominent and you may be at risk of vision problems
an "inactive" phase – when the condition has "burnt out" and many of the symptoms settle down, but you may be left with some long-term problems (including protruding eyes)
Typically, the initial active phase lasts for between several months and around two years.
Some of the main treatments you may be offered if you have thyroid eye disease are described below.
Correcting thyroid hormone levels
If you have an overactive thyroid gland (hyperthyroidism) or an underactive thyroid gland (hypothyroidism), you will usually be offered medication to help correct the level of thyroid hormones in your blood.
For example, an overactive thyroid can be treated with medication such as thionamides, which prevent your thyroid gland producing excess amounts of thyroid hormones.
Treating your thyroid problems will not necessarily improve your eye-related symptoms, but it may help prevent other problems associated with abnormal thyroid levels. It may also help the problems affecting your eyes from getting worse.
You may also be advised about things you can do, and treatments that are available, to relieve some of the symptoms associated with the active phase of thyroid eye disease.
stopping smoking if you smoke, as it can significantly increase the risk of eye problems becoming more severe
raising the head of your bed – for example, by using extra pillows – which may help reduce some of the puffiness around your eyes
wearing sunglasses if you have photophobia (sensitivity to light)
trying to avoid exposing your eyes to irritants such as dust
using eye drops to help relieve soreness and to moisten your eyes if you have dry eyes
wearing glasses containing special prisms designed to help correct double vision
If your thyroid eye disease is mild, these measures – along with the medications to correct your thyroid hormone levels mentioned above – may be all the treatment you need.
In more severe cases, when the eyes are particularly painful and inflamed during the active stage of thyroid eye disease, a type of medication called a corticosteroid may be recommended by your doctor.
Corticosteroids are powerful medications that can help bring the inflammation associated with thyroid eye disease under control, and can help ensure the condition is stable before any type of surgery (see below) is considered.
In many cases, corticosteroids given directly into a vein (intravenously) will be recommended, because taking corticosteroid tablets over a long period of time can have significant side effects.
A typical course of treatment with intravenous corticosteroids will involve weekly treatments over a 10-12 week period. You should start to notice an improvement in your condition after a week or two.
Severe side effects of intravenous corticosteroids are uncommon, but you may experience some short-lived problems for a few days following the treatment sessions, such as feeling agitated, having difficulty sleeping, headaches, and blushing of the neck and face.
Occasionally, orbital or retrobulbar radiotherapy may be considered during the active stage of thyroid eye disease if corticosteroids have not been effective. It may also be combined with corticosteroids.
This treatment uses high-energy radiation, usually X-rays, to destroy cells. Low doses of radiation can be used on the tissues and muscles in the eye socket to help reduce the swelling.
During treatment, you will lie down and a special shell will be placed over your head to keep it still. A machine will then be used to carefully direct beams of radiation at the area being treated.
This is usually done on an outpatient basis, which means you won't need to stay in hospital overnight, and will typically involve around 10 treatment sessions over a two-week period.
Radiotherapy can cause some side effects, although these should be minimal as the treatment will be confined to a specific area and shouldn't affect other parts of your body. However, possible side effects may include the short-term worsening of your eye symptoms,cataracts and, in rare cases, sight-threatening retinopathy (damage to the layer of tissue at the back of your eye).
In some cases, surgery may be considered as a treatment for exophthalmos if you have severe or persistent symptoms.
For example, surgery may be considered to improve the appearance of the eyes if exophthalmos has been in the inactive phase for a few months, as medical treatment alone will not necessarily reverse the protrusion of the eyes.
It may be carried out during the active phase of thyroid eye disease as well if there is an immediate threat to your vision due to compression of the optic nerve (which transmits signals from the eye to the brain).
Surgery may also be effective if the exophthalmos is caused by other problems, such as issues with the blood vessels behind the eyes.
Types of surgery
There are three main types of surgery that may be carried out on people with exophthalmos, although it is unusual for someone to have all three. These are:
orbital decompression surgery – (see below) where a small amount of bone is removed from your eye socket(s)
eyelid surgery – where surgery is carried out to improve the position, closure or appearance of the eyelids
eye muscle surgery – where surgery is carried out on your eye muscles to bring your eyes into alignment and reduce double vision
These procedures are usually carried out under general anaesthetic, which means you will be asleep. Depending on the type and extent of the operation you have, you may need to stay in hospital for up to a few days afterwards.
Orbital decompression surgery
Orbital decompression surgery is most often carried out to improve the appearance of the eyes of people with thyroid eye disease who are affected by exophthalmos. It may also be required to reduce any pressure on the optic nerve.
During the procedure, a small amount of bone will be removed from your eye sockets (orbits) and some of the fat surrounding the socket may also be removed.
This allows any excess tissue that is pushing the eyeballs forward to move down into the space below. It also allows your eyes to sit further back in your head, so they do not protrude forward as much.
This procedure is carried out under general anaesthetic and will normally involve making incisions near where your eyelids meet in the inner corner of your eyes (the point nearest the nose). You may need to stay in hospital for a day or two after this procedure, so your recovery can be closely monitored.
Possible complications that can occur following orbital decompression surgery include persistent double vision, a build-up of blood in the eye socket (haematoma), and an infection where the incision is made.
If you are considering having orbital decompression surgery, ask your doctor or surgeon to explain the benefits and risks of the procedure to you.
Treating other causes of exophthalmos
For most other problems that cause exophthalmos, treatment will vary, depending on the underlying cause.
For example, if you have an infection affecting the tissue in your eye socket, such as cellulitis, your ophthalmologist may prescribe antibiotics to treat the infection. They may also need to carry out a procedure to drain any abscesses that have developed.
If you have a tumour behind your eye, your doctors will discuss treatment options with you. For most types of cancer, treatment will involve one or more of the following:
chemotherapy – where medication is used to kill the cancerous cells
radiotherapy – where radiation is used to kill the cancerous cells
surgery to remove the cancerous tumour
If you have thyroid eye disease, your driving ability may be affected.
You are legally obliged to inform the Driver and Vehicle Licensing Agency (DVLA) about a medical condition that could have an impact on your driving ability.
The GOV.UK website provides information and advice on how to tell the DVLA that you have stopped driving or need to stop.