Glaucoma Evaluation
Patient Background: What is Glaucoma?
Glaucoma is the name given to a group of conditions in which the optic nerve suffers a characteristic form of damage at the back of the eye which is often associated with a raised level of intraocular pressure. The optic nerve damage causes patchy loss of vision that varies in severity from patient to patient. Without treatment, the loss of vision usually gets worse over the course of many months or several years. The loss of vision in glaucoma is permanent, but with early treatment, the damage to vision can be minimised. Appropriate examinations are essential to detect glaucoma early and prevent significant sight loss, as most patients with glaucoma are not aware of problems with their vision. This is because the central vision (for reading and recognising people) is only affected when glaucoma has advanced to a late stage. Even when central vision is still good, glaucoma may affect the vision needed for driving and getting about (for instance, seeing steps). Blindness from glaucoma is rare.
Glaucoma Risk Factors
Glaucoma is found in about 2 per cent of the population over the age of 40. It can also affect children and young adults, although much less frequently. The great majority of those with glaucoma have a chronic (slowly developing) form of the condition, primary open angle glaucoma (POAG), and studies have demonstrated that half of all cases remain undiagnosed. People of African-Caribbean origin are far more at risk of POAG than Caucasians. Close blood relatives of patients with POAG have at least a four-fold increased risk of glaucoma compared with those without a family history of glaucoma. People from families in which a member has glaucoma should be tested for glaucoma from the age of 35 onwards. People with other glaucoma risk factors in addition to the family history (e.g. being of African-Caribbean origin, having diabetes, smoking or short-sighted) should be tested from an even earlier age.
POAG usually affects both eyes, but initially produces few symptoms. Eventually,
if untreated, sufferers may become aware of a severe restriction of their
field of vision or even loss of central vision in the worse eye. Although
blindness from glaucoma is uncommon, it is the leading cause of preventable
blindness in the UK. A significant risk factor for glaucoma blindness is
advanced loss of vision when the condition is first detected.
What causes glaucoma?
A certain level of pressure is needed within the eye
for it to keep its shape. This pressure is maintained by the flow of a
fluid (aqueous humour) within the eye. A balance between the fluid entering
and leaving the eye determines the pressure in the eye (the intraocular
pressure -- IOP). Most cases of glaucoma occur because the flow of fluid
out of the eye becomes restricted and the pressure within the eye rises.
This pressure causes damage to the optic nerve.
In some eyes with glaucoma, the pressure is not high. In these cases it
is thought that a poor blood supply or a weakness in the optic nerve fibre
structures may make the nerve susceptible to damage by normal eye pressure.
This is known as normal tension glaucoma. Some eyes can have moderately
raised eye pressure but no sign of loss of vision or optic nerve damage
and this is known as ocular hypertension. Most treatments for primary open-angle
glaucoma are intended to lower the IOP to generally as low a pressure as
possible with minimum adverse effects. There are an extensive range of
eye drops available which our consultants will discuss with you.