- written by Dr Arun Kumar
Glaucoma is a disorder of the eye characterised by damage to the optic nerve (nerve responsible for vision). Though in many cases it is due to the increased pressure in the eye, some individuals can develop glaucoma even with normal eye pressure.
Glaucoma is the second leading cause of blindness in the world, according to the World Health Organisation. In India at least 12 million people are affected and nearly 1.2 million people are blind due to glaucoma.
Aqueous humor is a clear watery fluid that flows inside of the eyes. The production and drainage of this fluid maintains the pressure inside stable. If the outflow of aqueous humor doesn't work properly either due to overproduction or pathology in the drainage system, fluid builds up. This increases pressure inside the eyes, damaging the optic nerve. It is a progressive disease, which is manifested initially as visual field loss and ultimately can lead to irreversible blindness if left untreated.
All glaucomas are characterised by progressive optic neuropathy resulting in a specific pattern of irreversible visual field defects with characteristic optic disc appearance. This is due to the death of retinal ganglion cells (RGCs).
This is the most common type of glaucoma. In this the eye’s drainage canals becomes clogged over time causing increase in the internal eye pressure. Most people with open angle glaucoma present as a chronic disease and do not have any early symptoms. Initially the loss of vision is only peripheral (side) vision. As the optic nerve is more damaged, there is progressive vision loss till only the central vision is left resulting in tunnel vision (as if looking through the end of a narrow tunnel).
2. Primary angle closure glaucoma (PACG):
Also called Narrow angle glaucoma, this type of glaucoma presents acutely. In this the angle between iris and cornea becomes too narrow resulting in blockage of the drainage canal and the eye pressure raises very quickly. This is called an acute attack and requires immediate medical attention.
Signs of acute angle closure glaucoma attack:
In some people this also develops slowly as a chronic angle closure glaucoma with no initial symptoms, patients know it when there’s an acute attack or when the damage is severe.
3. Normal tension glaucoma:
In this type, people have eye pressure within the normal range, but show signs of optic nerve damage and blind spots in their field of vision. The exact cause of normal tension glaucoma is not known. This is also called normal-pressure or low-tension glaucoma.
Secondary glaucomas result from predisposing conditions like eye injury, inflammation (uveitis), use of certain drugs and advanced cases of cataract or diabetes. Congenital glaucomas present in babies born with defective development of the eye's drainage canal in their prenatal period. It may present at birth or develop in the first few years of life.
5. Pigmentary glaucoma:
In this, the pigment granules from your iris (the colored part of the eye) break into the clear fluid produced inside the eye. These granules build up in the drainage canals and slowly clog them, causing elevated eye pressure.
A regular comprehensive eye checkup can help detect glaucoma in its early stages, before significant damage occurs. This is important in preventing loss of vision or to delay its progress. A complete eye examination by your Ophthalmologist will include the following:
Other specialised tests like confocal laser scanning ophthalmoscope and scanning laser polarimetry are available for early detection.
Early detection and appropriate management is the best way to prevent irreversible vision loss due to glaucoma. Knowing your risk factors, regular screening will help in early detection. Once diagnosed, regular treatment and followup will help preserve your quality of vision.
written by DR. ARUN KUMAR
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