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What is Glaucoma?
Glaucoma is a condition in the eye in which the pressure inside the eye is raised leading to damage to the optic nerve and progressive blindness. There are two types of Glaucoma, a primary glaucoma with heriditary factors and a secondary glaucoma due to some disease or as a sequell to some disease of the eye. Glaucoma can also be precipitated by drugs, poisoning, and may be a result of injury to the eye, or as a result of a metabolic disease like diabetes.
Primary Glaucoma may be of two types, one with an Open Angle and the other with a Closed angle. Normally Aqueous Humor, the liquid in the anterior chamber of the eye (please refer to diagram below), is formed by the ciliary body of the eye, and flows from the ciliary body – between the lens and the iris – throught the pupil – into the anterior chamber of the eye. From here it is drained through the trabecular meshwork into the venous system of the eye. (See diagrams below)
In Primary open-angle glaucoma (also called Chronic Open Angle Glaucoma) (Abbr. POAG ro COAG) (please refer to the diagram below), the drainage of the aqueous humor is affected due to clogging of the trabecular meshwork for unknown reasons. The angle formed between the peripheral cornea and the iris is normal. Thus called “open-angle” glaucoma.
In Primary closed-angle glaucoma (please refer to the diagram below), the drainage of the aqueous humor is hampered due to a very narrow or nearly absent angle formed between the iris and the peripheral cornea and the iris and the lens at the level of the pupil. Thus called “closed-angle” glaucoma.
If one of the two mechanisms are precipitated due to a local disease of the eye, or a systemic disease affecting the eye, or drugs, or poisoning, or trauma to the eye, it is a secondary glaucoma.
The symptoms of glaucoma
Unfortunately Glaucoma is an insidious disease. There may be few symptoms in the early stages or none at all. So for people with a family history of glaucoma, it is always better to get an eye check up done at regular intervals for early detection of glaucoma starting at 25-30 years of age.
Narrow-angle glaucoma can appear as sudden pain in the eye with reduced vision, or foggy vision, watering from the affected eye, and headache. More than one such episode may occur in the early stages of narrow-angle glaucoma. This is a medical emergency – if unattended may cause blindness. In the more chronic cases the pressure may be permanently raised and nerve defects occur, ultimately leading to a painful hard and blind eye.
Whereas in open-angle glaucoma there may be mild headaches in the front of the head, but usually the condition is first noticed when the patient complains of bumping into objects on the ground or just above the head level. The optic nerve damage has already begun. In the end stages, the eye is hard, painful and blind.
(See the progression of glaucomatous optic nerve damage below)
The medical management of glaucoma
Two principles are involved in the medical management of glaucoma.
1. Drain more aqueous to reduce the intra-ocular pressure, and
2. Reduce the production of aqueous humor to reduce the intra-ocular pressure.
3. The third indirect objective is to prevent damage to the optic nerve by using a group of drugs called neuro-protectors. This latest entry shows promising results. But the main aim of therapy in glaucoma is to control intra-ocular pressure with drugs so as to prevent damage to the optic nerve. (Please refer to the diagrams below)
The surgical management of glaucoma –
1. Treatment by LASER – Trabeculoplasty and iridotomy (please refer to the diagrams below)
2. Surgery – Surgical Iridotomy and Trabeculectomy (please refer to the diagrams below)