Thyroid eye disease is the most common condition affecting the eye socket (orbit) in the UK. It is more common in females than males and is seen mostly between the ages of 20 and 60.
For the most part TED is seen in patients with dysfunction of the thyroid gland. This is usually secondary to the immune system (antibodies) acting against the thyroid gland resulting in an increase in thyroid hormones circulating in the bloodstream.
For reasons we do not fully understand the same antibodies that affect the thyroid gland also affect the tissues in the eye socket.
The immune reaction in the eye socket results in inflammation and expansion of the structures within the orbit including the conjunctiva lining the eye, the orbital fat and the muscles around the eye.
The inflammation is seen as injection and redness of the eye itself and the eyelids. The enlargement of the fat and muscles can give rise to classic appearance of thyroid eye disease whereby the eyes are pushed forwards giving. This can result in an angry or startled appearance. In some cases this gives rise to exposure and discomfort of the eye. If the muscles around the eye are particularly affected one can experience a squint with secondary double vision. The muscles of the eyelids can be overstimulated which further adds to the appearance of eyelid retraction.
In severe cases the vision can be affected. This is usually due to exposure of the surface of the eye (the cornea) or due to pressure on the nerve behind the eye (the optic nerve). This is seen in cases when the fat or muscles within the eye socket expand significantly.
Hence TED can affect the eyes in the following way:
- Puffiness and redness of the eyelids (lid swelling)
- Eyelid retraction giving the staring appearance.
- Dry eye symptoms due to exposure of the surface of the eye.
- Movement of the eyes forward (exophthalmos) due to expansion of fat and muscle (further adding to the staring appearance).
- Double vision (diplopia) or squint secondary to the eye muscle involvement
- The eye socket may ache, particularly on eye movement.
TED often lasts between 18 months and two years. The inflammation will often accelerate (the active phase) over the first few months and then gradually improve over the following 12-18 months. The severity of the condition (i.e the degree of double vision, change in appearance or reduction in vision) may also worsen over the first few months and then gradually improve. The aim of treatment is to try and reduce the degree of inflammation and severity and the time it takes for improvement. Disease progression is very variable each patient can be affected in different ways; both in terms of symptoms experienced and duration of the condition.
During the active inflammatory phase we use drugs to suppress the immune system and reduce the secondary symptoms. The medications used involve both steroids and non-steroidal treatments. In most cases if steroids are required they will be given intravenously. Commonly used non-steroidal treatments include Methotrexate, Ciclosporin, Azathioprine and in severe cases biological agents such as Rituximab. These medications all have side effects and require regular monitoring of blood tests. These will be discussed with you fully in the clinic and your general practitioner will also be involved in monitoring your treatments.
In severe cases of TED the medical treatment may not prevent a reduction in vision. In such cases surgery may be required to expand the eye socket to either (i) reduce the pressure on the optic nerve or (ii) improve the surface of the eye.
If you have double vision during this phase you may require occlusion or prisms attached to your glasses.
Once the inflammatory phase has settled (which may require the treatments as above) management is directed at the sequelae of TED which may involve surgery.
Such treatments include
i. Orbital decompression surgery to help the eyes sit further back in the eye socket
ii. Squint surgery (to reduce double vision)
iii. Eyelid surgery to improve the eyelid position and reduce the soft tissue enlargement of the upper or lower eyelids.
Often you may need to use lubricants to improve some of the discomfort associated with TED. You can also aim to sleep with more than one pillow and use cold compresses each day to try and reduce swelling around the eyes.
If you develop double vision you will need to inform the Driver and Vehicle Licensing Authority (DVLA) who will investigate your ability to drive safely.
Smoking is associated with worse outcomes in TED and it is imperative that if you smoke you either cut down or stop altogether.
Author: Mr Jonathan Norris FRCOphth