Tuesday, 26 July 2011

Preventing Damages from Glaucoma

Published in City Times

Preventing damages from Glaucoma

Glaucoma is a treatable disease which can happen without manifesting any symptoms for several years. It is for this very reason that it is a dangerous disorder which if left untreated, can damage the optic nerve and the visual field without a patient being aware of it until it is too late. Left untreated it could cause permanent vision loss and blindness. It affects certain races of people more than others and most usually it is related to advancing age though it can affect younger age groups of people and also newborns. In adults, treatment to lower the eye pressure can help prevent the development of glaucoma damage and slow the worsening of damage that has already occurred. Once damage has occurred, it cannot be reversed. Therefore, the goal of treatment is the prevention of more glaucoma damage, not the reversal of pre-existing damage and this is best done by routine eye checkup for people above the age of 40. If at 40, a person’s eye pressure is normal, and there are no risk factors, a two-yearly checkup is fine. However, if risk factors are present, an annual checkup is a must, emphasizes Dr.Nadim Habash,Consultant Ophthalmologist, American Hospital, Duabi.

What exactly is glaucoma and how does it happen?
Glaucoma is a condition in which the eye's intraocular pressure (IOP) is too high, causing structural and functional damage to the optic nerve, assuming that the blood supply to the optic nerve is normal. The IOP is too high, either because the eye is producing too much fluid, or because it's not draining properly.

How common is glaucoma in any given population?
While it is hard to put down figures on the incidence of the condition, it is more common among Asians, African-Americans and people from the Middle East, as compared to Europeans and White Americans. The reasons for this difference are purely genetic.

What age groups of people are commonly affected by it?
Glaucoma can happen at any age. However, Angle Closure Glaucoma (ACG) is more common among women who are far sighted or hyperopic and who are above the age of 40. Open Angle Glaucoma (OAG) is common among men and women, usually above the ages of 40 or 50, though it can also happen in younger age groups of people. But the older the age of the individual, the higher the chance of developing OAG.

So there are different types of glaucoma? And are ACG and AOG the only forms?
Broadly there are two categories of the condition: angle closure glaucoma (ACG) and open angle glaucoma (OAG) and sub groups within OAG. In addition we have Secondary Glaucoma which is usually the result of infection (like inflammation of the iris, termed iritis) or trauma and injury to the eye. The injury may be physical – penetrating or blunt injury to the eye, as well as chemical injury, resulting in glaucoma.

Another very important entity is drug-induced glaucoma, mainly caused by topical or systemic steroids. People who use steroid eye drops should be aware of the fact that this can lead to glaucoma if not used properly, under medical supervision.

But steroids are the mainstay of treatment in certain medical conditions like asthma for instance. So are these people on steroids at higher risk of being affected with glaucoma?
Yes. That’s why most people who are on topical or systemic steroids for any medical condition, should have their eyes tested regularly for glaucoma.

But would such eye checkups and consequent early detection of glaucoma, prevent the condition from happening?
No, not in people who are prone to increased eye pressure. But we can at least detect the problem early and prevent the damage that is caused by glaucoma though we cannot prevent the glaucoma itself from happening. Again, having said that, not every patient who is on steroid treatment need get glaucoma; about 25% of the population are more prone to developing glaucoma if they are on steroids.

What are the other causes of glaucoma and are they different from ACG and OAG?
Anatomically, the eye is such that when the pupil dilates, it changes the folding of the iris and it reaches the angle of the eye where it blocks the fluid from reaching the angle. The angle of the eye is the site where the fluid goes and drains out of the eye into the blood vessels. ACG is an anatomic variation that the patient is predisposed to. AOG is also an anatomic variation, but the IOP is due to deposition of a material called mucopoly saccharide in a structure in the angle of the eye called the trabecular meshwork. This meshwork has a number of pores which get blocked by the mucopoly saccharides in certain groups of people. Diabetics are more prone to this form of glaucoma. Having said that, we don’t know why some people who do not have diabetes and other risk factors, develop it. In both instances of glaucoma, there is a certain hereditary factor involved.

What are the symptoms of Glaucoma?
ACG usually presents itself suddenly and in an acute form. Symptoms of the condition include burning sensation in the eyes, pain, halos around the eyes, headache and blurred vision. Because the very high eye pressure can rapidly damage the optic nerve, acute angle closure is a true emergency and requires immediate treatment by an ophthalmologist, which is mostly surgical. Sometimes, however, subacute and chronic ACG can occur.

OAG is the low grade chronic glaucoma. The pressure builds up slowly over a period of years and people don’t feel this happening. Most often, this condition is discovered accidentally when they visit the eye doctor for some other problem. OAG is the most dangerous form because it is a hidden condition that is silently happening for several years perhaps, without any kind of manifestation whatsoever. So the manifestation, most of the times, is late presentation of damage that has already happened!

How is glaucoma diagnosed?
Confirmation of glaucoma is by 3 tests. Firstly, we measure the IOP. This is basically done in two ways. One is the "puff test" which shows up a slightly higher reading of the IOP and is therefore less accurate. The other method, the most important and accurate one is by measuring IOP by pressing an instrument called an applanation tonometer against the eye to determine how much resistance there is.

Secondly, we check for optic nerve damage by dilating your eyes. The hallmark optic nerve damage from glaucoma is abnormal "cupping", which is an abnormal depression in the center of the part of the optic nerve that is visible to the ophthalmologist.

Thirdly we do the visual field testing by using the automated perimeter which detects peripheral changes in the visual field that are caused by glaucoma.

So, if the IOP is high, the optic nerve and visual field are damaged, we can say that the person is suffering from glaucoma. But this does not mean that all these three factors have to be abnormal for a person to have glaucoma; one of the three factors could be abnormal and the person can still have glaucoma.

But are these 3 abnormalities specific to glaucoma or are there other eye conditions that could present with these abnormalities?
Yes, that’s possible. Visual field changes, for instance can occur in other eye conditions. Similarly, there are certain changes in the optic nerve which look like glaucoma but are not glaucoma. So it is for the ophthalmologist to judge the situation and if necessary, do other tests to rule out other eye conditions which are not glaucoma but present with similar findings.

Does glaucoma always affect both eyes?
Most of the times, it is bilateral, affecting both eyes. Also, most of the times it is more advanced in one eye than the other. However, occasionally, you can have unilateral glaucoma or glaucoma affecting one eye only.

How is glaucoma treated?
For ACG, treat is surgical and the surgery is not necessarily taking the patient to the OT. We use a special laser called YAG which allows us to make a certain hole in the iris, near the angle of the eye to drain out the fluid.

The treatment for OAG includes medication, surgery and laser. The first line of treatment is with anti glaucoma medication, usually in the form of drops and very rarely oral medication. We normally start with one particular medication suited to the patient’s condition and add further medication. These drops act, either to reduce the secretion of the fluid in the eyes or they work on opening the angle of the eye to allow more drainage of the fluid. If the pressure is not controlled medically with the drops, or if the patient is not compliant with the treatment or the treatment is not working, then we switch to surgical treatment. Various surgical techniques may be used depending on the patient’s needs.

Are there side effects to the medications used?
Yes, there are. Some of the medicines can cause topical side effects like burning sensation, itching and allergic response. Certain other anti glaucoma medications that we give, have systemic side effects which affect breathing and heart rate. Hence we avoid giving certains groups of medication to heart and asthma patients. In such patients, we choose appropriate medication to suit their condition.

What is congenital glaucoma?
This is a condition affecting newborns who are genetically prone to it, especially in communities where marriage among relatives is common. Unfortunately, though detected and diagnosed early, the only treatment is surgical. And the prognosis following surgery is not very good and most of these children will require multiple surgeries.


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