Stages and Tests for Glaucoma
In my last article, we discussed some of the key things to know about glaucoma; now we will discuss the stages and tests for glaucoma.
Why is primary open angle glaucoma a "multi-factorial" disease?
Glaucoma is a disease where the nerve tissue (neurons) connecting the eye to the brain are lost. For the first 200 years since its discovery in the 1800's, glaucoma was thought to be a disease caused by high pressure inside of the eye. However, it has been since realized that this is only one piece of the puzzle. We now perform many different tests for glaucoma, and you can read about each below.
Glaucoma: Tests, Signs, and Symptoms
Eye Pressure - Sign of Risk
80% of glaucoma patients will have high eye pressure readings. Likewise, patients with high eye pressure are at increased risk for developing glaucoma. All eye exams require eye pressure testing.
Corneal Thickness - Sign of Risk
Corneal thickness is the best predictor of if a patient will develop glaucoma. Corneal thickness does not change so only has to be checked on the initial glaucoma evaluation. Thin corneas have been found to be an independent risk factor for glaucoma.
Family History - Sign of Risk
Glaucoma has a genetic component. The more people in your family with glaucoma the higher the risk. Genetic testing also may reveal you carry a genetic disposition, but is not very reliable for this disease and not recommended.
Angle Closure (Gonioscopy) - Sign of Acute glaucoma
Gonioscopy rules out the most dangerous forms of glaucoma- the forms which progress extremely quickly. This is done by the use of a contact lens device and mirrors to help the examiner see the fluid drainage system of the eye. It should only be done every 5 years for most glaucoma patients; some need it more often.
Optical Coherence Tomography (OCT) - Sign of Early Glaucoma
The OCT has made early diagnosis of glaucoma possible since 1996. Thanks to this technology and improvements in treatment, there is little to no reason that any patient who attends to regular eye exams should ever go blind from glaucoma. It is important you make sure your optometrist has the newest OCT technology because quality of these machines vary.
Optic Nerve "Cupping" - Sign of Early, Moderate, and Late Glaucoma
Increased cup to disc ratio is one of the most important signs of glaucoma. The cup to disc ratio represents the thickness of the neural tissues entering into the optic nerve. This tissue thickness gives us a clue to how many neurons are connecting your eye to your brain. Glaucoma is defined by the thinning of these tissues. All eye exams require optic nerve examination.
Visual Fields - Sign of Severe Glaucoma
The visual field is a test of your peripheral (side) vision. When a patient loses their side vision, loss occurs slowly and the patients central (best) vision remains. Therefore, patients never notice the loss of side vision. A single visual fields tells the examiner very little about a patients glaucoma, several fields must be compared in a row for useful data.
Vision Loss - Symptom of End-stage Glaucoma
When a patient starts noticing symptoms of glaucoma, over 95% of their neurons connecting the eye to the brain have already been lost. Sadly, there is no way to reverse glaucoma. The only symptoms of primary open angle glaucoma is vision loss (blur).
What You Need to Know
Sometimes all the tests can become overwhelming. The most important things to remember about primary open-angle glaucoma is that it is a very slow progressing disease and preventative treatment is extremely successful for almost all patients. However, you will not notice your glaucoma, there are no signs until the last 5% of tissue loss, and by that time it is too late to return you to being fully sighted- so it is extremely important for glaucoma suspects to attend regular checkups with an eye care professional.
Lysle Shaw-McMinn, O.D.
Written for This Blog on Oct 13, 2014
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