Glaucoma is a disease of the optic nerve that affects approximately 60 million people globally. It is the second most common cause of blindness, leaving an estimated 7.5 million people blind. In India it affects 11 million people, of which 1.5 million are blind. Though there is no cure for this condition, doctors can help preserve remaining vision and enable patients to live a full life.
In glaucoma the field of vision decreases so gradually that often the patient does not realize the problem till it is too late.Glaucoma has been called the ‘sneak thief of sight’ because it usually causes blindness without any symptoms.
What Causes Glaucoma?
Eyes constantly produce a clear fluid called aqueous humor, which is different from tears, which bathes and nourishes different regions of the eye . Normally the fluid drains out of the eye through a 'drainage canal' located in the 'angle' of the eye , 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.
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.
Who is at Risk?
A complete eye examination - not only the usual reading of the chart - is mandatory, especially after the age of 40.
Those at risk of developing glaucoma include:
Actually, everyone should have a comprehensive eye examination periodically as it can help detect other preventable, controllable, or treatable diseases such as retinal detachment, diabetic eye disease, and cataract.
How is Glaucoma Diagnosed?
Since the treatment methods for open angle and angle closure glaucoma are different, it is important to identify the mechanism involved. The diagnosis (or exclusion) of glaucoma requires a detailed and comprehensive eye examination.
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.
For open angle glaucoma, initially eye drops are used to lower IOP; your doctor will select the one most suited for your condition. If the disease is advanced, and/or medical treatment fails, surgery may be necessary.
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.
In some patients glaucoma may be controlled by medicine alone, while others may need laser treatment or surgery. Surgery usually involves cutting a piece of tissue from the angle of the eye and allowing the fluid to accumulate under the transparent skin that surrounds the eyeball. However, glaucoma surgery is not as predictable as cataract surgery and carries more risks, including loss of the eye from devastating bleeding or infection. It is usually used if drugs fail to control eye pressure, or for socioeconomic considerations.
Non-penetrating surgery can also help decrease eye pressure and has fewer complications than the standard approach. But its results are not as good. Hence it is not a first line of treatment for glaucoma.
In cases with poor potential for visual recovery or function, a different kind of laser may be used to reduce eye pressure. This is usually reserved for advanced cases.
Need for Constant Care
Life long monitoring is essential, the frequency of follow up visits depends on the individual case. At each visit most of the tests may be repeated to determine the progression of the disease and to decide whether change in treatment is needed.