What is 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.

Glaucoma detection (Investigation)

Measuring the pressure in the eye using special Instruments (Tonometry ? Schiotz / Applanation). Viewing the optic nerve by shining light into eye (direct & indirect opthalmoscopy. Viewing the angles of anterior chamber by special lenses (Gonioscopy). Testing field of vision ? (Perimetry) by showing a sequence of spots of light on a screen & asking which ones are seen. HRT-II ? Analyses 3 dimensional images of the optic nerve head & the retina in a rapid & accurate manner. It helps to distinguish normal & glaucomatous eyes & assessment of progression of glaucoma. It also analyses the RNFL thickness. Treatment: The main aim of Treatment is to reduce the pressure in the eye. The patient needs to go to hospital for regular checkups & Treatment. Treatment usually started with eyedrops to lower the pressure. These act by reducing the amount of fluid production or by opening up the drainage channels. If this doesn't help, doctor may suggest either laser treatment or an operation called a trabeculectomy to improve the drainage. The doctor will discuss which is the best method in your particular case. If there is an acute attack, you must go to hospital immediately. so that pain & pressure in the eye can be relieved. If treated early, pressure can usually be brought under control in a few hours. Glaucoma if diagnosed without delay & treated promptly & effectively there may be almost complete & permanent recovery of vision. Delay may cause loss of sight in the affected eye & LOSS OF VISION IN GLAUCOMA IS IRREVERSIBLE. Bringing the pressure under control will not restore lost vision but only prevent further deterioration.

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