Glaucoma is a group of eye diseases in which the retinal nerve fibres are damaged leading to progressive optic nerve damage resulting in decreased vision or even blindness. It is an important reason for poor quality of life due to loss of vision resulting in difficulty in near vision, working in dim light and driving.
In glaucoma the field of vision decreases so gradually that often the patient does not realize the problem till it is too late. Since it usually causes blindness without any symptoms, glaucoma has been called the 'sneak thief of sight'.
Our eyes constantly produce a clear fluid called aqueous humor (Fig 1 & Fig 2), which bathes and nourishes different regions of the eye (this is different from tears). Normally the fluid drains out of the eye through a 'drainage canal' located in the 'angle' of the eye (Fig 2), the junction between the cornea and the iris. In persons with glaucoma, the fluid does not drain out as freely as it should, thus increasing the pressure inside the eye, known as intraocular pressure (IOP).
The optic nerve carries all sensations from the retina to the brain. Raised IOP damages the optic disc (that part of the optic nerve that is inside the eye is called the optic disc).
Glaucoma can sometimes occur with a statistically "normal" IOP. Hence the vulnerability of the optic disc is another factor that needs to be considered. Accordingly, the diagnosis of glaucoma requires more than just the mere measurement of intraocular pressure.
Most types of Glaucoma cause no symptoms. Central vision stays normal until very late in the disease. If Glaucoma remains untreated, people may notice that although they see things clearly in front of them, they miss objects to the side and out of the corner of their eye. It seems as though they are looking through a tunnel.
It is important to realize that there is no cure for glaucoma. Once nerve fibers die and visual function is lost, it cannot be recovered. Treatment can only help preserve remaining vision; hence it is imperative to detect the disease in its earliest stage.
The management of glaucoma must be an individualized effort. Simplistically speaking, in angle closure glaucoma doctors use a laser to create an alternative path for the fluid to drain out. However, this approach works for early cases; advanced cases require medication and surgery as for open angle glaucoma. An attack of closed angle glaucoma is an emergency and the IOP must be lowered as soon as possible to prevent damage to the optic nerve.
Medical therapy is expensive, and likely to be life-long. As with any treatment, there is a risk of side effects. Sometimes the side effects may be more uncomfortable for the patient, and less acceptable, than living with the disease. Therefore doctors consider the risk-benefit ratio of the treatment options for glaucoma. The main criterion is how much functional capacity is affected rather than the actual degree of vision loss. Your doctor will select the treatment most suited for your condition, please follow the advice meticulously.