Primary open angle glaucoma
The build up in pressure in this condition is very slow. Therefore visual loss is gradual and patients often do not notice any problem until there is evidence of severe visual impairment. The peripheral (or side) vision is affected first and therefore the eyesight is not obviously affected. These peripheral areas of visual field loss increase until eventually the central vision is damaged leading to blindness.

Because primary open angle glaucoma is not usually recognised until it is advanced, people are screened for the condition as part of the optician's routine examination when eye tests are carried out. The optician will check the pressure, examine the nerve at the back of the eye and test the field of vision if this is indicated. As primary open angle glaucoma is rare in people under the age of 40, these screening tests are usually only carried out after this age.

Primary angle closure glaucoma
In this condition the pressure inside the eye rises rapidly and the eye becomes very painful. It is usually red and the vision becomes blurred. The patient may notice haloes around lights. There is often significant headache and occasionally the patient feels very unwell and may even vomit. This condition is very rare in patients under the age of 50 and is more common in people who are long-sighted.

Other types of glaucoma
The symptoms of other types of glaucoma vary, depending on the underlying cause.