What is Glaucoma?
Glaucoma is an eye disease caused by increased pressure within the eye. This increased eye pressure damages the optic nerve (the connection of the eye to the brain). If left untreated, glaucoma may result in a slow loss of nerve function, which results in blind spots in the vision and eventually total blindness.
Glaucoma has been called the “silent thief of sight” because it occurs painlessly, even unnoticeably. Many patients with glaucoma comment that their vision “feels fine.” In the early stages, glaucoma has no symptoms and can only be diagnosed with a thorough eye health exam. However, as glaucoma remains untreated, a person will slowly lose their peripheral and eventually their central vision. This is why it is critical to have regular visits. Glaucoma, if detected early, is very treatable. Vision can be preserved and blindness can be prevented.
What causes Glaucoma?
No one knows exactly what causes glaucoma, but some factors increase your chances of having it:
- older age
- family history of glaucoma
- African, Asian or Hispanic descent
- a previous eye injury
- poor health (such as diabetes, extreme high or low blood pressure)
- regular, long-term steroid/cortisone use
How common is glaucoma?
It is one of the most common causes of blindness and affects 1 in 100 Canadians over age 40. Although it usually occurs in older people, it can develop at any age.
An instrument called the tonometer measures the pressure inside the eyes. The test is quick, easy and painless.
Visual Field Test
Visual field testing is important to measure the extent of optic nerve damage from elevated eye pressure. It helps to detect if you have lost any peripheral (side) vision, which is a sign of glaucoma.
A sophisticated computerized machine tests your peripheral vision and allows us to know if any vision is being lost. At the end of this test, a printout of your visual field is produced. New software has been developed to help us analyze these results as well as monitor progression of visual field loss over successive tests.
A number of new and highly sophisticated image analysis systems are now available to evaluate the optic nerve and retinal nerve fiber layer, the areas of the eye damaged by glaucoma. These devices include scanning laser tomography (e.g. HRT3), laser polarimetry (e.g. GDX), and ocular coherence tomography (e.g. spectral-domain OCT). These instruments can help us by giving a quantitative measure of the anatomical structures in the eye. Photographs of the optic nerve can also be useful to follow the progression of damage over time. Large databases have been established to compare an individual’s anatomic structures to those of other patients in the same age group.
We have a variety of diagnostic tools which aid in determining whether or not you have glaucoma — even before you have any symptoms. Let us explore these tools and what they do.
An ultrasound instrument is used to measure the thickness of your cornea (the front, clear part of the eye). Measuring your corneal thickness is also important since recent studies have found that having thin corneas is a strong predictor of developing glaucoma in patients with high IOP.
Drops are placed in your eyes to widen, or dilate, the pupils. Using a variety of instruments, we can look directly through the pupil to examine the optic nerve for signs of damage. Its color and appearance can indicate whether or not damage from glaucoma is present and how extensive it is. This technique remains the most important in diagnosing and monitoring glaucoma.
We can also perform gonioscopy to closely examine the area where fluid drains out of the eye. In glaucoma, it is important that the fluid drains out of the eye freely. A special type of hand-held contact lens, with mirrors inside, is placed on the eye. The mirrors enable us to view the interior of the eye (called the angle) from different directions. In this procedure, we can determine whether the angle is open or narrow. Individuals with narrow angles have an increased risk for a sudden closure of the angle, which can cause an acute glaucoma attack. Gonioscopy can also determine if anything, such as abnormal blood vessels or excessive pigment, might be blocking the drainage of the fluid out of the eye.