Thyroid eye disease
Thyroid eye disease (thyroid orbitopathy or TO) is a condition that causes the muscles and soft tissues of the eye socket to swell. It happens when you have a problem with your thyroid gland. You may also hear it being called Graves’ disease.
How the eye works
We need light to see what is around us and its colour. Light bounces off the objects we look at and different objects reflect different amounts of light.
Light rays enter the front of your eye through the clear cornea and lens. It’s very important that both the cornea and lens are clear as this allows the light to pass directly through the front of your eye to the retina. The cornea and lens bends light so that it can focus on the retina at the back of your eye. This gives us a clear, precise image. The cornea focuses the light towards your retina and the lens fine tunes this focusing of light.
The tears form a protective layer at the front of your eye and also help to direct the light coming into your eye. Your iris, the coloured circle at the front of your eye, changes the size of the pupil which is the dark hole in the middle of the coloured part of your eye. The pupil gets smaller in bright conditions to let less light in and gets bigger in dark conditions to let more light in.
The middle of your eye is filled with a jelly-like substance called the vitreous. The vitreous is clear and allows light to pass directly from the front to the back of your eye.
The retina at the back of your eye is a light-sensitive layer which consists of rod and cone cells. These cells collect the light signals directed onto them and send them as electrical signals to the optic nerve.
Rod cells are concentrated around the edge of the retina. They help you to see things that aren’t directly in front of you, giving you a rough idea of what is around you. They help with your mobility and getting around by stopping you from bumping into things. They also enable you to see things in dim light and to see movement.
Cone cells are concentrated in the centre of the retina where the light is focused by the cornea and lens. This area is called the macula. Cone cells give you your detailed vision which you use when reading, watching TV, and looking at people’s faces. They are also responsible for most of your colour vision.
Our optic nerve is made up of thousands of nerve fibres. It’s the pathway for light signals to travel to your brain. The brain processes these signals to allow you to “see” the world around us.
Seeing can be likened to the process of taking pictures on a film with a camera which you then get developed. The retina is like a camera film which stores an image of what you are looking at. The image directed onto your retina is then sent along to your brain where it is processed, like developing a camera film. Therefore you actually “see” in your brain with the light information sent to it from your eyes. This whole process happens very quickly so that everything you see is in focus.
About thyroid eye disease
Thyroid eye disease (thyroid orbitopathy or TO) affects the soft tissues such as the fat and muscles surrounding our eyeball within the eye socket. The condition is characterised by a period of inflammation and swelling of these tissues, followed by a healing response.
The condition most commonly occurs in association with an overactive thyroid gland, but can also occur if you have an underactive thyroid gland; an identical picture sometimes occurs when the thyroid gland itself is not affected.
The thyroid is one of our body's endocrine glands; these are glands which produce hormones. Hormones are chemical messengers in our blood streams, which co-ordinate long term changes in function. The thyroid is located in the neck just below the Adam’s apple, and its hormones regulate our metabolism.
Diseases of thyroid
The effect of thyroid disease is felt to be as a result of either an over-activity or under-activity of the gland, and therefore either a speeding up or a slowing down of metabolism.
Autoimmune disease and the thyroid
The main problem affecting the thyroid is autoimmune disease. Our immune system normally makes small proteins (antibodies) to attack bacteria and other ‘germs’ that are foreign to us. If you have an autoimmune condition, your immune system makes antibodies to act against normal tissues of your body. At the moment the reason for this is not entirely clear. Thyroid cancers can also occur.
Why thyroid problems affect the eyes
When an auto-immune attack starts on your thyroid, it responds by producing more of its hormones. At the same time the antibodies attacking your thyroid gland also attack the tissues around your eyes.
You may find it helpful to know more about thyroid problems, and this is available from the British Thyroid Association.
How thyroid disease affects the eyes
The commonest problem is dry eyes. This is because, in autoimmune disease, more than one organ may be attacked, and commonly the thyroid and all the orbital contents (the soft tissues around the eye), including your lacrimal gland, are attacked by your immune system. The lacrimal gland produces the tears in our eyes, so when it is affected fewer tears are produced.
As a result, your eyes may feel dry and gritty. It is worth noting that although your eyes may be described as “dry” they can water and produce more tears than normal.
As the orbital contents (the soft tissues around the eye) become inflamed, they become red and swollen. Let’s have a look at some of the changes to your eyes you may notice:
- Your eyelids can become puffy and red (lid swelling)
- The muscles of your eyelids can contract, producing a staring appearance (called lid retraction)
- The muscles and fat surrounding your eye can swell, pushing your eyes forward so that they bulge out of the orbits (called exophthalmos)
- Lid retraction and exophthalmos can make the dry eye symptoms worse
- The swelling of the muscles which move your eyes produces unequal movements and can cause you to see double vision (diplopia)
- The orbits may become painful, particularly on eye movement.
How thyroid disease affects your sight
If your eye muscles become swollen, then this can affect how well the muscles are able to control the ability of your eyes to move together. This can cause you to see double vision. This is a symptom which occurs when your eyes do not quite point in the same direction and therefore each sends a slightly different message to your brain. When this happens your brain “sees” two of everything. It can make activities like reading very difficult and driving very dangerous.
The law states that if someone develops double vision then they must stop driving. It is illegal to drive with double vision which isn't controlled. If you do develop double vision then the law requires you to inform the Driver and Vehicle Licensing Authority (DVLA) and usually they will contact your ophthalmologist for a medical report. If your double vision then becomes controlled with glasses at a later date then DVLA may declare you fit to drive again. Not informing the DVLA of double vision could invalidate your insurance and you would also be driving illegally.
In severe thyroid eye disease, especially in younger patients whose firm tissues do not allow the eyes to bulge forwards, the pressure inside the orbits increases, compressing the optic nerve and causing sight problems. Your optic nerve carries the messages from your eye to your brain and can be damaged by pressure.
If the pressure starts to compress your optic nerve sight may become dim, colours begin to look washed out, and your visual field may constrict. If this starts to happen, then it’s important to seek medical attention as soon as possible, to reduce the pressure on your optic nerve before permanent damage occurs.
The treatment options for optic nerve compression are steroids, immunosuppressant drugs, orbital radiotherapy and emergency orbital decompression surgery. These all aim to lower the pressure on your optic nerve and hopefully avoid permanent damage.
Treatment for thyroid disease
The first priority is to deal with the primary thyroid problem. This is firstly with anti-thyroid drugs, and then with either surgery or radiotherapy. The treatment of an overactive thyroid often produces an underactive thyroid, which then requires treatment with thyroid replacement therapy. It’s important to be aware that the treatment of the underlying thyroid condition can often make your associated eye condition worse, and to be prepared for this.
Treating thyroid eye disease
When the eyes are dry and gritty then the best treatment is to use lubricating eye drops (artificial tears). These can help to make your eyes feel more comfortable and help to prevent your eye being damaged by being so dry.
Treatment for double vision
An orthoptist (an eye professional who specialises in double vision) will usually be involved in your treatment for this. Different treatments may be used depending on whether the double vision is temporary or permanent.
One of your eyes can simply be covered up so that the brain receives only one image.
Prisms work by bending light in a direction which compensates for the angle between the eyes. They can be tailored to match the angle between your eyes, and fixed to spectacles. Stick-on prisms, often called Fresnel prisms, may be used temporarily until it is established that the angle is stable, at which point prisms can be incorporated into your normal spectacles by an optometrist.
During the active stages of TO, your double vision may be temporary and unstable, so prisms and occlusion may be the only treatment appropriate. As TO burns out (fades away), however, it may often leave some residual double vision which may require surgical treatment.
Long term effect of thyroid orbitopathy
In the majority of cases the active inflamed stage of TO burns itself out in about two years, leaving a variable amount of scarring, with lid retraction, exophthalmos or double vision.
If, after the thyroid orbitopathy has burned itself out, there are still problems with the eyes (including exophthalmos, lid retraction and double vision), then it may be necessary for you to decide whether or not to have further surgery to help improve these things. Sometimes the problems that are left may only be minor and you may feel it isn't necessary to have more treatment, or that the risks of the surgery outweigh the problems that you have. However there may be cases where surgery is a more obvious choice.
If surgery is needed then it is carried out in the sequence of orbital decompression surgery, then surgery to the muscles of the eye, then surgery for double vision, and finally surgery to correct the lid position.
Orbital decompression is carried out to place the eyes further back in the orbits where they belong. This is normally done by removing a small amount of bone from inside the orbit of your eye so that the eye can sit further back in its socket. Occasionally fat may also be removed from the inside of your orbit. One of the main risks of this surgery is the development or worsening of double vision, so you may expect to need muscle surgery as well after this surgery. There is also a small risk of serious sight problems with this surgery.
If you are left with stable permanent double vision, surgery is the treatment of choice to correct this. This surgery lengthens the muscles of the eye so that the eyes are brought back into alignment. It’s usually done with an adjustable suture technique. Muscle surgery may alter the position of the eyelids and so you may expect to need lid surgery as well after muscle surgery.
Lid surgery will aim to correct the position of the upper and lower eyelids over your eyes, allowing them to close properly.
To have any of this surgery it’s important for your thyroid disease itself to be stable and for the active phase of the orbital disease to have burnt out. Because of this some ophthalmologists believe that early low dose radiotherapy given early in the active phase of the TO can help improve the outcome after the TO has burnt out.
All this means that if you are left with problems once the TO has burnt itself out, then you could face a series of operations to improve your vision. Typically these operations are carried out over about 18 months to 2 years.
With modern surgical techniques, very few people are left to cope with the difficult after-effects of TO. The modern surgical techniques now aim to restore the position, function and appearance of your eyes to as near to normal as possible.
Sources of support
Whether you have just been diagnosed with thyroid eye disease or have been living with it for a while, at RNIB, we are here to help and support you at every step.
105 Judd Street
The RNIB Helpline is your direct line to the support, advice and products you need. We'll help you to find out what's available in your area and beyond, both from RNIB and other organisations.
Whether you want to know more about your eye condition, buy a product from our shop, join our library, find out about possible benefit entitlements, be put in touch with a trained counsellor, or make a general enquiry, we're only a call away.
Tel: 0303 123 9999
We’re ready to answer your call Monday to Friday 8.45am to 5.30pm.
The Thyroid Eye Disease Charitable Trust (TEDct) can provide information, care and support to those affected by thyroid eye disease.
PO Box 1928
Tel: 0844 800 8133
The British Thyroid Foundation aims to provide information and support for people with any kind of thyroid problems and their families.
3 Devonshire Place,
Tel: 01423 709707 / 709448
Other useful contacts
Driver and Vehicle Licensing Agency (DVLA) can give you advice on sight standards for driving.
Drivers Medical Group
Tel: 0300 790 6806
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