A disease of the optic nerve, glaucoma affects approximately 60 million people worldwide. Approximately 7.5 million people are blinded by it, making it the second most common cause of blindness. There are 11 million people affected in India, of whom 1.5 million are blind. Doctors can help patients preserve their vision and enable them to live a full life, even though there is no cure for this condition.
What is Glaucoma?
Glaucoma affects the field of vision so gradually that many patients do not realize the problem until it is too late. Glaucoma has been called the ‘sneak thief of sight’ since it usually causes blindness without showing any symptoms.
What Causes Glaucoma?
Our eyes continuously produce a clear fluid called aqueous humor, which bathes and nourishes different regions of the eye (this is different from tears). Normally fluid drains out of the eye through a ‘drainage canal’ located at the junction of the cornea and iris, the ‘angle’ of the eye. Those suffering from glaucoma see their fluid drain out less freely than it should, which increases the pressure inside the eye. This is called intraocular pressure (IOP).All sensations are transmitted from the retina to the brain by the optic nerve. IOP increases damage to the optic disc (the part of the optic nerve inside the eye is called the optic disc).IOP can sometimes be “normal” even when glaucoma occurs. Hence, the vulnerability of the optic disc must be taken into account. Hence, glaucoma cannot be diagnosed by simply measuring intraocular pressure.
Types of Glaucoma
There are several types of glaucoma, all of which increase IOP and damage the optic nerve.
IOP rises in open angle glaucoma due to an increase in resistance to the outflow in the canal. There is a gradual onset of this type, and symptoms may not be evident until the damage has been done. The patient may lose their peripheral vision, leaving them with only central vision. Older people are more likely to lose peripheral vision.
Angle closure glaucoma is characterized by a relative blockage of fluid flow, resulting in elevated pressure. People with long-sightedness are more likely to suffer from this condition. The symptoms are dramatic in the rarer acute cases and include severe eye pain, headaches, nausea, reduced vision, and seeing rainbow coloured rings around lights.
A stress, anxiety, or reading attack may also precipitate one, which may resolve on its own, but recur after some time.Chronic angle closure glaucoma is the most common type of angle closure glaucoma. In this case, the ‘drainage canal’ is shut off by the iris, just like in open angle glaucoma.
The third type is developmental glaucoma, which is further divided into congenital glaucoma (occurs in newborns) and juvenile glaucoma (occurs in children and young adults).
Glaucoma and high IOP may also be secondary and caused by other factors, such as the use of steroid drops without a prescription. Such drops cannot be used without monitoring the intraocular pressure.
Those With Risk of Glaucoma
After the age of 40, a comprehensive eye examination is essential, not just a chart reading.
Those at risk for glaucoma include:
Over 35 years of age (risk increases with age);
Those with glaucoma in their families;
Those who use steroid drops, tablets, or creams;
Those with diabetes, hypertension, and eye injuries;
Those who wear minus glasses for short-sightedness;
Any person complaining of pain, redness, or watering in the eyes; and
Lights that appear to have colored rings around them.
A comprehensive eye examination periodically can help detect other preventable, controllable, or treatable problems such as retinal detachment, diabetic eye disease, and cataracts.