Glaucoma is a term that describes a group of eye disorders resulting in irreversible optic nerve damage, which causes visual field test defects and can lead to blindness. Glaucoma is usually associated with high intraocular pressure.
Only about half of those who have glaucoma are aware that they have the condition while most patients with glaucoma are not aware of problems with their vision because the central vision (for reading and recognising people) is only affected when glaucoma has advanced to a late stage.
Normal visual field
Visual field in Glaucoma
One of the most important things an ophthalmologist needs to know about a glaucoma patient is how fast the disease is progressing over a period of time, determining that requires multiple visual field test exams over a period of time. Glaucoma can cause blindness if left untreated. When glaucoma develops, usually you don’t have any early symptoms and the disease progresses slowly. In this way, glaucoma can steal your sight very gradually. It is not sure why this happens, there are many theories why the ganglion nerve fibers that comprise the optic nerve are damaged in glaucoma , including vascular (high pressure decreases nerve perfusion), mechanical (pressure at the optic nerve causes axoplasmic flow to back up) and neuroprotective, but high intraocular pressure certainly seems to be associated, if not entirely the cause, of optic nerve death.
Chronic (primary open-angle) glaucoma is the most common form of this disease. However, other forms also occur:
- Low-tension or normal tension glaucoma. Occasionally optic nerve damage can occur in people with so-called normal eye pressure. This form of glaucoma is treated in the same manner as open-angle glaucoma.
- Acute (angle-closure) glaucoma. Acute glaucoma is when the pressure inside the eye rapidly increases due to the iris blocking the drain. An attack of acute glaucoma is often severe. People suffer pain, nausea, blurred vision and redness of the eye. Immediate medical help should be sought. If treatment is delayed there can be permanent visual damage in a very short time. Usually, laser surgery performed promptly can clear the blockage and protect against visual impairment.
- Congenital glaucoma. This is a rare form of glaucoma caused by an abnormal drainage system. It can exist at birth or develop later. Parents may note that the child is sensitive to light, has enlarged and cloudy eyes, and excessive watering. Surgery is usually needed.
- Secondary glaucomas. These glaucomas can develop as a result of other disorders of the eye such as injuries, cataracts, eye inflammation. The use of steroids (cortisone) has a tendency to raise eye pressure and therefore pressures should be checked frequently when steroids are used.
Although anyone can get glaucoma, some people have a higher risk, those with
- a family history of glaucoma
- short sightedness (myopia)
- long sightedness (hyperopia)
- eye injuries
- blood pressure
- past or present use of cortisone drugs (steroids)
People in these groups should have their first eye check no later than the age of 35. For most people, it is recommended to have an eye check for glaucoma by the age of 40.
Without treatment, glaucoma first causes peripheral vision loss. Even when central vision is still good, glaucoma may affect the vision needed for driving and getting about (for instance, seeing steps). The loss of vision usually gets worse over the course of many months or several years. The loss of vision in glaucoma is permanent and eventually can lead to blindness, but with early treatment, the damage to vision can be minimised.
Glaucoma cannot currently be prevented, but if diagnosed and treated early it can usually be controlled. Medication or surgery can slow or prevent further vision loss.
Globally, glaucoma is the second leading cause of blindness (behind cataracts), according to the World Health Organization.
Glaucoma most often occurs in people over age 40, although a congenital or infantile form of glaucoma exists. People with a family history of glaucoma, African Americans over the age of 40, and Hispanics over the age of 60 are at an increased risk of developing glaucoma. Other risk factors include thinner corneas, chronic eye inflammation, and using medications that increase the pressure in the eyes. As the population becomes older, the proportion of glaucoma patients is increasing.
There is no cure for glaucoma. Vision lost from the disease cannot be restored. However, there are treatments that may save remaining vision. That is why it is so important to detect the problem as early as possible, to be able to start treatment with as little damage to the vision as possible.