What is Glaucoma?
Glaucoma is the name given to a group of eye diseases that cause progressive damage to the optic nerve of the eye. The optic nerve conveys visual signals from the eye to the brain. Good vision depends on a healthy optic nerve. If the optic nerve is damaged, blindness occurs. This blindness is irreversible.

What causes it?

At the front of the eye, there is a small space called the anterior chamber. Clear fluid called aqueous humour flows in and out of the chamber, to bathe and nourish nearby tissues . In glaucoma, for various reasons, the fluid drains too slowly out of the eye. As the fluid builds up, the pressure inside the eye rises. Uncontrolled pressures cause damage to the optic nerve and loss of vision.

It was once believed that all glaucomas were caused by high pressures within the eye (known as intraocular pressure – abbreviated as IOP). It is now established however, that even people with a normal IOP may suffer from glaucoma. Today raised Intraocular pressure is considered only as a “Risk Factor” for glaucoma, along with other factors such as racial ancestry, family history, high myopia and increasing age.

In most cases, glaucoma appears after the 4th decade of life, and its frequency increases with age.

Who gets Glaucoma?

Glaucoma is a worldwide disease affecting approximately four per cent of the global population. It is the second leading cause of blindness in the world. Glaucoma affects one out of 200 people aged 50 and younger, and one out of every 10 people over the age of 80. Research shows that in 2010, an estimated 60.5 million people globally will be living with either angle-closure glaucoma or primary open angle glaucoma. An estimated 50 per cent of glaucoma cases remaining undiagnosed.

In the developed world, glaucoma is not common among persons under the age of 40, but the prevalence increases with age. In the developing world, the disease can affect all ages.

Other risk factors include raised pressure inside the eye, those who have myopia, and people with thinner corneas. People who have immediate relatives with glaucoma have a higher chance of developing glaucoma.

Those of African descent are three times more likely to develop a type of glaucoma called primary open angle glaucoma. Many East Asian groups are prone to developing another form known as angle, closure glaucoma, due to their shallower anterior chamber. Women are three times more likely than men to develop angle-closure glaucoma due to their smaller anterior chambers.

If the condition is detected early enough, it is possible to arrest the development or slow the progression of this disease with medical or surgical treatment.

How do I know if I have glaucoma?

Glaucoma usually begins silently during midlife with painless, gradual vision loss. At first, there are no symptoms. Vision stays normal, and there is no pain. However, as the disease progresses, a person with glaucoma may notice ‘blind spots’ at the outer edges of the field of vision. As damage to the optic nerve gets worse, these blind spots increase and gradually the peripheral vision shrinks leading to a ‘tunnel vision’. That is, objects in front may still be seen clearly, but objects to the side may be missed. Finally the remaining central vision is also lost.

This progressive loss of vision occurs over a long period of time and is often only recognised when the disease is quite advanced. It is for this reason that Glaucoma has been nicknamed the “sneak thief of sight”. Once lost, the damaged visual field can never be recovered.

Only one type of glaucoma called ‘angle-closure glaucoma’ is associated with symptoms of red and painful eyes. Symptoms of angle-closure glaucoma can include headache, nausea/vomiting and visual disturbances, like coloured halos around lights.

Types of glaucoma

There are several types of glaucoma. The most common are the two adult-onset glaucomas namely, Primary Open Angle Glaucoma (POAG), and Angle-Closure Glaucoma (ACG), which is more common in patients of Asian ancestry.

Some glaucomas occur as a complication of other visual disorders (the so-called “secondary” glaucomas). “Secondary glaucomas”, can be caused by prolonged use of steroids (steroid-induced glaucoma); Restricted blood flow to the eye, as seen in diabetic retinopathy and vascular occlusions (neovascular glaucoma); Injuries to the eye (angle recession glaucoma); Internal inflammations of the eye (uveitic glaucoma) and many more.

Certain types of glaucoma may occur at birth (“congenital”) or during infancy and childhood (“juvenile”).

Glaucoma in uncontrolled diabetes (Neovascular glaucoma) deserves special mention. It is a type of secondary glaucoma that is difficult to treat. This condition is often caused by advanced diabetic retinopathy . Neovascular glaucoma results when abnormal blood vessels grow into the drainage channels of the eye causing a block in the outflow of fluid form the eye. Patients with this condition rapidly lose their eyesight. A new treatment for this disease, involving use of a group of medications known as Anti-VEGF agents shows good promise.

Who diagnoses and treats glaucoma?

Eye physicians and surgeons (ophthalmologists) are medical doctors who have undergone specialised training in order to treat eye diseases and to perform surgery. They are best qualified to diagnose glaucoma.

Screening for glaucoma is usually performed as part of a standard eye examination. Many people are familiar with the “air puff” method used to measure eye pressure in an eye examination. But, this test alone cannot detect glaucoma. Glaucoma is found most often during an eye examination through dilated pupils. This means drops are put into the eyes during the exam to enlarge the pupils allowing the eye doctors to see more of the inside of the eye. Doctors check for changes in size or shape of the eye, and do an examination of the optic nerve to look for any visible damage to it. Other tests like anterior chamber angle examination or Gonioscopy and a formal visual field test are also performed.

The retinal nerve fiber layer can be assessed with imaging techniques such as optical coherence tomography (OCT), scanning laser polarimetry, and scanning laser ophthalmoscopy. Examination for glaucoma should be done with more attention given to sex, race, history of drugs use, refraction, inheritance and family history.

How is glaucoma treated?

The modern goals of glaucoma management are to avoid glaucomatous damage to the optic nerve, preserve visual fields and provide a good quality of vision for the patient. This requires appropriate diagnostic techniques, regular follow up examinations and a careful selection of treatments tailored to each individual patient. Although intraocular pressure is only one of the major risk factors for glaucoma, lowering it via various medications and surgical techniques is currently the mainstay of glaucoma treatment.

The primary goal of treatment is to preserve vision. The typical first line of treatment is eye drops which lower the intraocular pressure either by helping fluid leave the eye or by reducing the amount of fluid produced in the eye. Some patients may need to take a combination of two or more eye drops or even eye drops plus medications in tablet-form to effectively lower the pressure.

The second line of treatment involves the use of lasers. During laser surgery, a beam of laser light is focused on the part of the anterior chamber where the fluid leaves the eye. This opens up the drainage channels making it easier for fluid to exit the eye. Over a period of time, the effect of laser surgery may wear off. Patients who have this form of surgery may have to continue taking glaucoma drugs.

Traditional glaucoma surgery is the third line of treatment. It is indicated when medications and lasers fail to check the progress of glaucoma. Through surgery, alternate pathways are fashioned for the controlled release of the excess pressure.

Conclusion

There is no absolute cure for glaucoma as yet. Medications or surgery can only halt or slow-down the progression of visual loss. Visual loss is always irreversible. Therefore early detection of glaucoma is very essential. Your eye-doctors can detect glaucoma in its early stages and advise you on the best course of action.

Irregular medications and skipping follow-up visits to the doctor are a major reason for vision loss in glaucoma patients. A 2003 study of patients in Europe, found that half of them had failed to regularly take their medications the first time and one in four failed to refill their prescriptions a second time. Patient education and communication is extremely important in any successful treatment plan for this lifelong disease.