Glaucoma damages the optic nerve of the eye and may result in blindness. Open-angle glaucoma is the most common form of the disease and has no symptoms initially. Over the years it can steal sight and early detection can protect against serious vision loss and blindness. Glaucoma is also termed the ‘silent thief of vision’. The eye's optic nerve connects the retina with the brain and a healthy optic nerve is essential for good vision.
Glaucoma Damaging the Optic Nerve
Our eyes need a certain amount of pressure to keep the eye healthy. When the pressure increases, it results in glaucoma. Most cases of glaucoma have a raised intraocular pressure, but glaucoma can also occur with ’normal’ pressure, because the optic nerve is more liable to damage because of particular weakness, this is termed normal tension glaucoma (or NTG). It is important to note that eye pressure is independent of blood pressure.
Controlling Pressure in Eyes
There are a layer of cells behind the iris (the ciliary body) that produce a watery fluid called aqueous. This fluid passes through the pupil to leave the eyes via tiny drainage channels. Eye pressure increases if too much fluid is produced or it can't escape. When the optic nerve is under too much pressure, it can be injured. The extent of injury depends on the amount and the duration of the pressure. Very high pressure will damage the nerve immediately but even ‘low’ pressures can damage the sight gradually.
Different Types of Glaucoma
There are primarily four types of glaucoma:
This type of glaucoma gets its name because the angle that allows the fluid to drain out the anterior chamber is open. The fluid passes too slowly and as the fluid builds up, the pressure inside the eyes rises. The eye pressure rises slowly and there is no pain as such. Vision deteriorates with time.
Acute angle closure glaucoma
Acute angle closure glaucoma happens suddenly and a narrow angle prevents the fluid from getting to the drainage channels. The condition is quite painful and causes permanent damage to sight if not treated immediately. This is more common in Asian people than in Caucasians.
It is also called low-tension or normal-pressure glaucoma. In this type of glaucoma the optic nerve gets damaged even though the eye's pressure is not very high. The exact cause of normal-tension glaucoma is not known. Increased blood viscosity, hypoperfusion, hypercoagulability, etc. can be some of the contributing factors behind this type of glaucoma.
Congenital glaucoma occurs in babies because of incomplete or incorrect development of the drainage canals. The condition is quite rare and can be inherited. Through microsurgery, the structural defects can be corrected.
Symptoms of Glaucoma
One of the dangers associated with open angle glaucoma is the eyesight may seem perfectly normal and there is no pain as such. Vision is damaged slowly and if left untreated, people may miss objects on the side and corner. Suddenly they realise that there is no side vision and gradually the entire vision is lost. The other symptoms are:
- Blurred vision
- Severe pain in eyes and head
- Nausea accompanied with severe eye pain
- Coloured halos
Detection of Glaucoma
Most people think that they have the disease if pressure within the eyes gets increased. This is not true. High pressure makes one vulnerable to the disease. It all depends whether the optic nerve can tolerate pressure without being damaged and this varies from person to person. While normal pressure is between 12-21 mm HG, it has been found that people having this pressure also suffer from the disease. It is vital to have a thorough eye examination. Some of the tests conducted are as follows:
Visual acuity: This test measures how well one sees at various distances.
Visual field: This test measures peripheral vision and helps the doctor to find out if there is a loss of side vision.
Pupil dilation: Through this examination, the doctor gets a better view of the optic nerve and checks signs for damage. Close-up vision may remain blurred for a few hours after this test.
Tonometry: This is a standard test that determines the fluid pressure inside the eye and doctors use many types of tonometry tests.
Corneal thickness (CCT): This needs to be checked once as it can influence the accuracy of tonometry checks.
Although glaucoma can't be completely cured, it can be controlled. Early diagnosis and treatment is essential to protect sight. Using eye drops, eye pressure is lowered. These drops reduce the amount of aqueous produced in the eye or facilitate outflow. The drugs for glaucoma may be taken several times during the day. The drops may cause redness and burning in the eyes. One must tell the ophthalmologist if they are taking any other medicines. It is vital to take drops as long as they help control eye pressure. If medications don't provide adequate control, then patients may need to undergo laser treatment or microsurgery to improve drainage of fluids.