Glaucoma
Glaucoma is the name for a group of eye conditions in which optic nerve is damaged at the point where it leaves the eye. This nerve carries information from the light sensitive layer, the retina, to the brain where it is perceived as a picture. In some people, the glaucoma damage is caused by raised eye pressure. Others may have an eye pressure within normal limits but damage occurs because there is weakness in the optic nerve. Eye pressure is largely independent of blood pressure. A layer of cells (cilliary body) behind the iris produces a watery fluid, called aqueous. The fluid passes through a hole in the centre of the Iris to leave the eye through tiny drainage channels (Trabercular meshwork) which is in the angle between the front of the eye (Cornea) & the Iris and returns the fluid to the blood stream. Normally the fluid produced is balanced by the fluid draining out but if it cannot escape, then eye pressure will rise.
Different types of Glaucoma
1. Open angle glaucomas (chronic glaucoma): It is most common. The eye is anatomically normal, but blockage or malfunction of the drainage channels slowly over many years causes elevated eye pressure. There is no pain but the field of vision gradually becomes impaired. The analogy to the sink is a useful one. In a normal eye, the faucet is always on & the drain is always open. In open angle glaucoma the drain gets clogged, aqueous cannot leave the eye causing the fluid to backup. Since eye is a closed compartment, it causes pressure to build up within the eye. We need to use chemical cleaner (eye drops) to open the drain or turn down the faucet. If this is insufficient, we can stake the drain (laser trabeculoplasty) & if that doesn’t work. We need to put in new plumbing (surgery / implants)
2. Angle closure glaucoma (Acute glaucoma): The trabecular meshwork is normal, but the iris is pushed against the meshwork & there is sudden and more complete blockage to the flow of aqueous. It means the drainage channels are covered by a stopper & we need to remove the stopper (laser iridotomy). This glaucoma can be quite painful & will cause permanent damage to sight if not treated promptly.
3. Secondary and developmental glaucoma: When a rise in eye pressure is cause by another eye condition it is called secondary glaucoma. Glaucoma in childhood is called developmental or congenital which is caused by malformation in the eye.
Risk factors
People over the age of 45. It can develop in younger patients also. People with family history of glaucoma. People with myopia are more prone to develop open angle glaucoma & those with hyperopia are more prone to develop angle closure. Race ? persons of African originare more prone to develop POAG & closure more common in Asians.