What is glaucoma?
Glaucoma is a group of eye diseases where the optic nerve suffers a progressive and irreversible damage. The common cause is a high pressure inside the eye - called ‘intraocular pressure’ or ‘IOP’. The high IOP compresses the blood vessels at the optic nerve. If left untreated, this progressive compression of blood supply leads to irreversible damage to the optic nerve. The field of vision, that is our ability to see the objects in the sides of our vision-line is affected. Ultimately the loss spreads to larger areas and may lead to total blindness. The central vision remains remarkably intact till the final stages, and so the patient will not be aware of the ongoing progressive damage.

What are the types of glaucoma?
The common type is open-angle glaucoma. The other is the angle-closure glaucoma, which may be acute (occurring suddenly) or chronic (slowly progressing).

What causes glaucoma?
While the entire body is nourished by blood, an ‘aqueous humor’ nourishes the lens, iris and cornea. This wonderful gift of nature keeps the optical pathway of our eyes clear. This aqueous humor is secreted by the ciliary body. After nourishing the various structures at the front of the eye it is drained out though a series of drainage canals in the trabecular meshwork. This delicate filter is located around the outer edge of the iris. When this meshwork gets blocked and as the liquid continuous to flow into the eye, the IOP builds up, causing glaucoma.

What are the symptoms?
Most people who develop glaucoma notice no symptoms until vision is impaired. Usually the peripheral vision is affected first. In the late stages when the optic nerve is completely destroyed, blindness results.
In rare cases of acute angle-closure glaucoma symptoms develop suddenly and rapidly progress to blindness if not treated. The doctor must be immediately contacted if there is:

* Blurring of vision
* Severe pain and redness of the eye
* Nausea and vomiting
* Haloes around lights

Why is early detection and treatment important?
The vision lost due to glaucoma can not be regained, even after the surgery or other treatment. However a good control of eye pressure (IOP) by the means described above can help in preserving the vision or in minimizing the further damage. Hence it is very important to detect and treat the disease at an early stage before it has caused significant vision loss.

How can we detect glaucoma early?
Since this disease does not have any symptoms in the early stages, the only way to detect it early is by doing regular eye checkups, especially in those who are at a high risk for developing glaucoma.

How it is diagnosed?
Glaucoma is essentially a clinical diagnosis, assisted by various tests. Some of them are:

* Raised intraocular pressure as measured with a tonometre
* Increased cup-disc ratio as diagnosed by stereo-ophthalmoscopy
* Analysis of visual fields by computerised perimetry
* Optic nerve head scanning with Heidelberg retinal tomography
* Corneal thickness with ultrasound pachymetry.

Those with a family history of glaucoma or diabetes, who have frequent headaches, experienced frequent change of glasses etc., should seek a detailed glaucoma screening. Glaucoma screening also needs to be a part of routine eye check up for everyone at or above the age of 40 years.

What are the risk factors for glaucoma?
Glaucoma is more common in people above 40 years of age. Diabetes, minus power of glasses, eye injury, eye surgery, long term use of steroids tablets or drops, and a family history of glaucoma are other important risk factors. Persons with any of these risk factors must get regular eye checkups to detect glaucoma early.

How is it treated?
Treatment is by reducing the raised intraocular pressure by medications, laser or surgery. As the disease lasts lifetime, the medicines need to be used for lifetime, or till the surgery is performed. Periodic follow-ups are essential, even after a surgery, to see that the disease progression has stopped.

Medications are generally in the form of eye drops. Follow doctor’s advice meticulously. Don’t reduce the doses on your own or change the drops or its brand. Don’t skip the drops and don’t change the advised timings. Understand the disease and its treatment well. If you are on multiple eye drops, give a gap of atleast 30 minutes and if possible an hour between different medications. To instill the drops, pull the lower lid out and put only one drop into the eye, with the face lifted up, towards the ceiling. It can fall on any part of the eye, and this does not matter. Close the eyes immediately, and let them remain closed for about 2 to 3 minutes. Even if the drop spills over from the eye, there is no need to put a second drop. Indeed a very tiny portion of an eye drop is enough for it to act. Keep the dropper bottle in a cool clean place.

Lasers are of use in Narrow angle glaucoma. A hole is lasered in the iris so that the aqueous bypasses the pupil. Lasers role in open angle glaucoma is extremely limited.

Why is regular treatment and follow up important?
Even a single episode of high pressure can cause significant damage to the eye. Hence it is very important to use the drops and medicines regularly to control the pressure. The progression of the disease and the vision loss is generally not detectable by the patient. It is therefore necessary to maintain regular followups to document the change in vision, optic nerve changes and field defect, and to modify the treatment accordingly. For this purpose repeated tonometry, field checkup (perimetry) and other special investigations may be required. With the current treatments available, most of the patients maintaining regular treatment and follow up would be able to preserve their useful vision and can continue to lead a productive life.
 

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