Glaucoma: The silent thief of vision

Dr Bhavani Raina
Glaucoma (Kaala Motiya) is one of the leading causes of irreversible blindness in the world. It causes progressive damage to the nerve which is associated with carrying visual stimulus from eye to our brain leading to loss in vision and eventually blindness if left untreated. Glaucoma is responsible for 12.8% of blindness in India. The most commonly associated risk factor for this disease is raised intraocular pressure of the eye (pressure inside the eye) and most treatments at present are directed at reducing the intraocular pressure. The normal range of intraocular pressure is considered to be between 12 to 20 mm of Hg. The intraocular pressure is determined by the production and drainage of a fluid within the eye. This fluid is called aqueous humor and any imbalance between its production and drainage can lead to rise in internal eye pressure which in turn can cause glaucoma. This aqueous humor is present within a closed space in eye called as anterior chamber and depending upon the depth of this anterior chamber, glaucoma is broadly classified into open angle glaucoma or narrow angle glaucoma.
This disease is called the ‘silent thief of vision’ as symptoms usually start inconspicuously, progress slowly and patient has already lost a significant amount of vision by the time the disease gets diagnosed. The best way to prevent this is by going for a comprehensive eye check-up. Anyone can get glaucoma, but studies have shown that some people are at higher risk. In addition to high internal eye pressure, the risk factors for glaucoma include age more than 40 years, Asian or Hispanic races, people with family history of glaucoma, people wearing glasses with high minus number (myopes), and certain medical conditions like diabetes, hypertension, migraine, etc. Glaucoma can develop consequent to eye injuries and also due to prolonged usage of steroids. Rarely children can also suffer from this disease. Childhood glaucoma can be primary, or it may develop secondarily to other medical conditions.
Symptoms of glaucoma depend upon its type. In case of open angle glaucoma which is the commonest one, there is slow built up of pressure which damages the optic nerve. In some people the optic nerve is sensitive to even normal pressure and they are prone to develop glaucoma at normal range of internal eye pressure. This is called Normal Tension Glaucoma. There are no obvious symptoms in the initial stage. Later on patients may have some blurring or see blind spots in their peripheral field of vision. In advanced stage of the disease, the patients are left with central vision and total loss of peripheral vision and this is known as tunnel vision. Many patients notice a frequent change in the power of their reading glasses. Patients suffering from narrow angle glaucoma have more forthright symptoms such as mild headache, ocular discomfort especially when moving into a dark room and blurring of vision. An acute attack of narrow angle glaucoma is usually associated with severe headache, nausea, vomiting, and coloured halos along with sudden and gross loss of vision.
Once a patient is suspected of glaucoma the eye surgeon runs a battery of tests to establish the diagnosis. Internal eye pressure is measured using specialized instruments. The status of the drainage angle of the eye is assessed. The extent of damage to the optic nerve is determined and tests are done to find out the amount of reduction in the field of vision especially the side vision. Once the diagnosis is confirmed the next step is damage control. Glaucoma is an irreversible disease and the aim of treatment is to reduce progression of the disease. Treatment options for Glaucoma include drugs, lasers as well as surgery. All these modalities mainly work to reduce the intraocular pressure so that further death of nerve cells can be prevented. The goal of management is to reduce eye pressure to a target level at which optic nerve is no longer harmed. This target pressure varies from patient to patient and is determined by the doctor after starting the treatment and then following up with the patient at regular intervals. Hence, the compliance of the patient is very important.
Most drugs act by either reducing the formation of fluid within the eye or increasing its drainage from the eye. In many patients the disease process will come under control with a single drug but some may require more than one type of drug to prevent further damage. Laser treatment is aimed at widening the gaps at the drainage angle to increase the outflow of the fluid or provide a new opening for the fluid to be drained out from the eye. Surgery is used to create an alternate pathway for the fluid to leave the eye. Artificial implants are also used to enhance the drainage of the aqueous humor. While the easiest way to manage Glaucoma appears the use of eyedrops, however, many times in spite of maximum medical treatment, the glaucomatous damage continues and the doctor has to resort to other options like surgery and lasers. In developing world, the cost of treatment is also a factor that has to be taken into consideration in deciding which treatment modality to adopt especially for diseases like this which require lifelong management. Glaucoma medications can cause allergic reactions in a few patients and need to be discontinued in them. Such patients can be then managed surgically or a combination of minimum medication and surgery/laser.
Treating Glaucoma requires a multidimensional approach. As during early period, the disease is more or less asymptomatic, it requires a lot of effort to first convince the patient to start the treatment and then to persuade him/her to go for regular follow ups. Many patients stop the treatment midway either due to misinformation and ignorance or due to financial considerations. Some give up just because fatigue sets in. Making the treatment affordable will definitely enhance the patient compliance. At the same time constant counseling of the patient, community-based awareness programmes and easy access to health care will go a long way in our fight against blindness caused due to Glaucoma.
Routine eye screening/ checkup
Use Anti-glaucoma medications regularly as prescribed by doctor
Screening of blood relatives of patients with glaucoma
Regular monitoring of eye pressure
Control of associated risk factors like diabetes and hypertension
Self-medication especially use of steroids
Missing or stopping anti-Glaucoma medications
Ignoring symptoms like eye discomfort, pain or fall in vision
(The author is Additional Professor, Deptt. of Ophthalmology, AIIMS Jammu.)