What is primary open angle glaucoma?
Glaucoma is the name given to a group of eye conditions in which the optic nerve is damaged. The optic nerve transfers visual information from the eye to the brain and, if it is damaged, this can result in sight loss. Primary Open Angle Glaucoma (POAG) is the most common form of glaucoma in the UK, affecting approximately 2% of the UK population aged over 40 years, increasing to 4-5% of those aged over 80 years. It is more likely to affect people with a family history of the same condition and people of West African ancestry, including those with African-Caribbean ancestry. POAG is a slow developing condition that causes damage to the optic nerve. The condition is not painful and patients may be unaware that they have it until they have started to lose vision. The optometrist examining a patient for POAG, will look for the characteristic appearance of ‘cupping’ of the optic disc (the head of the optic nerve at the back of the eye). The optic nerve transfers visual information from the eye to the brain and can be examined with various special instruments. On testing the patient’s fields of vision, defects may be found that are typical of glaucoma. The pressure of the fluid inside the eye (known as the intraocular pressure) must be measured as it is usually raised in glaucoma. In a small proportion of patients, however, the pressure is within the normal range.
The eyeball is a sphere kept inflated by fresh clear fluid formed within the eye. This fluid drains away through a fine ring-shaped sieve of tissue, known as the drainage angle (or simply angle), situated within the eye at the edge of the cornea (the clear window of the eye) and from there into the bloodstream. This sieve is not directly visible, but it can be seen through a special contact lens containing a mirror. In POAG the fluid is unable to escape normally because the meshwork has become blocked. The blockage causes the pressure inside the eye to rise, and in time this can damage the optic nerve, causing loss of visual field and even blindness if the condition is not treated.
How is primary open angle glaucoma managed?
If your optometrist suspects you have primary open angle glaucoma, they will arrange further tests. If glaucoma is confirmed, you will usually be referred to a hospital eye clinic for ongoing care. Treatment aims to lower the pressure inside your eye. Most people start with pressure-lowering eye drops or a laser treatment. If these do not control the glaucoma well enough, surgery may be recommended. If these treatments do not work well enough, or if the condition is more advanced, surgery may be needed
