Glaucoma is the name given to a group of diseases in which the optic nerve is damaged. The commonest association is with high pressure within the eye (intra-ocular pressure) although other causes such as poor blood supply or secondary causes do occur.
Primary Open Angle Glaucoma (chronic)
This is the most common type of glaucoma in the UK. It is an important and dangerous condition as it causes no symptoms in the early stages and it is possible for someone to lose a considerable amount of vision before they realise they have a problem. It is often referred to as the thief of vision for this reason. This is why early detection is vital and all people over 40 should have regular visits to an optometrist for screening. It is important to have at least the 3 commonest tests at each visit including intra-ocular pressure, visual field testing and examination of the optic nerve. The thickness of the cornea has also been shown to be a risk factor for glaucoma and some optometrists (and all ophthalmologists who have an interest in glaucoma) will provide this test too.
As the optic nerve becomes damaged blank patches (field defects) occur in the peripheral vision. These gradually enlarge until there is only a small central island of vision remaining (often referred to as tunnel vison). Eventually without treatment glaucoma can cause permanent blindness.
Progressive loss of optic nerve tissue in glaucoma may occur over many months or years. Treatment Studies have shown that by lowering intra-ocular pressure the progression of the disease can be slowed or stopped and that in the majority of people vision can be preserved for their lifetime. The diagnosis and treatment should only be in the hands of an ophthalmic surgeon with a specialist interest and training in glaucoma as they will be best able to make the correct diagnosis and give the best treatment.
The majority of cases can be controlled with the use of eye drops which lower intra-ocular pressure There are many different types of drops available but the commonest first line treatments usually need only one drop a day so should not interfere with quality of life. Some people may experience mild side effects due to drops but this should be taken in context with the good that they are doing. In some people the disease progresses despite a maximum number of drops or the pressure lowering effect is insufficient. Surgery or laser treatments can then be used which can effectively give long term pressure control.
Ocular Hypertension (OHT)
This is the name given to the condition in which the intra-ocular pressure is higher than normal but has not caused glaucoma. Depending on the level of pressure and other risk factors treatment may or may not be recommended as only around 10% of people with OHT will develop glaucoma. It is however important to have regular monitoring as the development of glaucoma will not cause any symptoms.
Although much less common than open angle glaucoma, acute (or closed angle) glaucoma is just as important as it can cause permanent loss of vision in a very short time if not treated properly and promptly due to a sudden build up of very high pressure in the eye. Patients who are predisposed or at risk from acute glaucoma can often be recognised early either by the optometrist who may raise suspicion or by an ophthalmologist who can view the inside of the eye using a special types of lens (gonioscopy lens). If the eye is at risk it can be treated with a quick, safe and simple laser procedure (peripheral iridotomy) which will prevent the onset of acute angle closure glaucoma in most eyes (see arrow in picture on right).