Glaucoma is the name given to a group of eye conditions that cause damage to the optic nerve which results in changes to your field of vision. Glaucoma usually affects both eyes, but one more than another, and if left undiagnosed and treated can cause blindness. Early diagnosis and treatment can usually arrest the progress of the condition.
Fluid in the eye called aqueous humour usually drains out of the eye through small plug holes called the trabecular meshwork which is found just in front of the iris – the coloured part of the eye. In glaucoma this meshwork of drainage channels becomes blocked causing the pressure in the eye to rise. It is thought that this rise in pressure is responsible for damaging the nerve cells of the retina – the light sensitive layer lining the eye. When the retinal nerve fibres are damaged they become less sensitive to light which results in a reduction in sensitivity in the visual field. Left untreated the sensitivity of the retina reduces to zero causing in blindness.
The risk factors for developing chronic or acute glaucoma are:
- High Intraocular pressure
- Age over 40
- Family History of glaucoma (particularly siblings)
- Longsightedness with shallow anterior chamber angles
- Shortsightedness over -6.00
- Afro-Carribean, Eskimo or South-East Asian descent
- Use of inhaled or oral corticosteroids
The two main types of glaucoma are Acute Angle Closure Angle Glaucoma, and Chronic Open Angle Glaucoma.
Acute Closed Angle Glaucoma
Acute closed angle glaucoma is caused by a complete obstruction of the trabecular meshwork. This causes the pressure within the eye to rise to very high levels which causes damage to the optic nerve at the back of the eye. The rise in pressure (intraocular pressure) usually happens suddenly causing the eye to be red and painful and may result in nausea and vomiting.
Chronic Open Angle Glaucoma
Chronic open angle glaucoma is thought to be caused by microscopic changes in the trabecular meshwork. The rise in intraocular pressure only happens slowly and does not cause any symptoms. Sometimes the damage to the retina can occur without a measurable rise in intraocular pressure above normal levels.
How many people have glaucoma ?
Chronic Open Angle Glaucoma is the commonest form of the condition found in the mainly a disease of the over 40’s. About 2% of people over 40 years of age affected, but it is often found in as many as 10% of people aged over 75. It is also more common in people of black-African or black-Caribbean origins.
Acute Angle Closure Glaucoma is less common, affecting only about 0.1% of white European people, but it too is related to ethnicity with up to 1% of people of Asian origin affected.
Glaucoma treatment reduces the pressure in the eye, and this can be done with eye drops, laser treatment or surgery, but early detection of the condition is important because any damage cannot be reversed – the aim of treatment is to prevent or slow down further damage to the eye.
A regular Eye Examination will help to ensure that glaucoma is diagnosed early so that treatment can start. Without treatment glaucoma can eventually lead to blindness.
Glaucoma can be treated under the NHS at the Eye Unit, and in Dorset certain patients with glaucoma may be eligible for the Shared Eyecare Scheme. This is an arrangement whereby you can attend for your glaucoma follow up appointments with us instead of having to attend the Eye Unit. The results of your appointment are sent back to the Eye Unit who decide if your glaucoma is stable or not. If it is stable the Eye Unit will probably continue to allow you to be seen on the Shared Eyecare Scheme, but if your treatment needs changing we are not able to prescribe different drops for you because your Eye Unit consultant remains in charge of your care.
Alternatively, if you have glaucoma you can transfer all of your care to our glaucoma specialist optometrist and we then can make changes to your treatment as required without the need for you to return to the Eye Unit unless you require surgery. If you would like our glaucoma specialist to take over your care click here to book a Specialist Consultation for glacuoma.