What is Glaucoma?
Glaucoma is a disorder that involves progressive damage to the nerve of the eye, and if left untreated the disease will result in irreversible loss of vision. It is the second most common cause of blindness in Ireland, and is becoming more prevalent because we are living longer.
How do I know if I have glaucoma?
Typically, glaucoma is silent until the very advanced stage, when irreversible loss of peripheral (surround) vision has occurred, but it can be easily treated in the vast majority of cases (if caught in time). Therefore, it is essential that persons at risk of glaucoma are screened for the condition, so that appropriate treatment can be started before irreversible visual loss has occurred. The American Academy of Ophthalmology estimates that half of those with glaucoma are unaware that they are suffering from the condition.
Who should be screened for Glaucoma?
There are 3 important factors for glaucoma, and these include:
- Family history of glaucoma ( if age >40 years);
- Age >60 years (even in the absence of a family history of glaucoma);
- Thin cornea (a special device is required to measure this);
Other factors include abnormally high or low blood pressure, diabetes and near sightedness (myopia).
How is a Diagnosis of Glaucoma Made?
A diagnosis of glaucoma is made by an ophthalmologist, and can only be made following a comprehensive assessment, which should include the following:
1. Measurement of eye pressure, also known as intraocular pressure (IOP):
a. Eye pressure is typically between 10 and 20 mmHg, but is often elevated in glaucoma. However pressure can be normal in glaucoma (normal tension glaucoma) or be elevated in the absence of glaucoma (called ocular hypertension);
b. Corneal thickness can influence measurements of eye pressure (i.e. a thin cornea gives artificially low readings, and vice versa) and is measured by an instrument known as a pachymeter;
c. Examination of the drainage angle of the eye with a special lens (gonioscopy) is also advisable when assessing eye pressure;
2. Assessment of visual fields (peripheral vision):
a. When you look at an object, you also see the things around that object, and this is known as peripheral (or surround) vision; it is this very important peripheral vision which is irreversibly lost in glaucoma;
b. Any assessment of glaucoma should include testing of the peripheral visual field, and this is especially true because one rarely notices a slowly progressive loss of surround vision;
3. Assessment of the optic nerve:
a. The loss of peripheral vision in glaucoma is the result of damage to the nerve (known as the optic nerve) which carries information from the eye to the brain, with consequential loss of nerve fibers (which changes its appearance in a characteristic way).
b. Glaucomatous changes in the optic nerve can be detected by an ophthalmologist by examining the retina with a special lens. These changes can be assessed in more detail using a special scan called optical coherence tomography.
Therefore, the diagnosis of glaucoma is made by an ophthalmologist on the basis of the results of a comprehensive evaluation, which should include all of the above.
Of note, all of the technologies required for such an evaluation are readily accessible at the Institute of Eye Surgery at Whitfield Clinic.
What treatment do I need if I am diagnosed with glaucoma?
Reduction of the eye pressure is the aim of treatment in glaucoma. There are three ways to lower eye pressure in glaucoma, and these include;
- Eye drops;
- Laser treatment;
The best option for a given patient is made on a case-by-case basis, in consultation with his/her ophthalmologist.
The information above has been supplied by Prof. Stephen Beatty from the Institute of Eye Surgery who is based in Suite 14 at Whitfield Clinic. For more information on Prof. Beatty's practice visit: www.ioes.ie