A Patient's Guide To Glaucoma And Glaucoma Treatment

By Dr Gerard Chuah

Glaucoma is associated with a buildup of pressure within the eyes, which causes the damage to the optic nerves. Vision gets worse over time resulting in gradual loss of sight. Although glaucoma cannot be cured, it can be controlled with treatments. Glaucoma accounts for 40% of blindness in Singapore.

This book is written by Dr Gerard Chuah, a leading eye surgeon in Asia and also the Medical Director of the Asian Diabetic and Retinal Disease Center and his team of doctors. The book wonderfully summarized the symptoms and treatments options of glaucoma.

• Language: English
• Publisher: Faris Digital Solutions Pte Ltd
• Release date: Jan 9, 2015
• ISBN: 9789814645027

Book preview

Chapter 1

What is Glaucoma?

by Dr Gerard Chuah

Glaucoma is an important public health problem. In the United States, an estimated 2 million people have glaucoma or glaucoma related conditions. 44% of the 2 million people are visually impaired, with 3% being legally blind (defined as vision worse than 6/60 or visual field no greater than 20 degrees in the widest diameter). In Asia, it is estimated that 3% of the population above 40 years old will develop glaucoma. The World Health Organisation has estimated there are more than 6 million cases of blindness worldwide due to glaucoma.

Blindness due to glaucoma is irreversible, unlike other eye diseases such as cataracts or retinal detachments, where some amount of vision can be restored after successful surgery. The only way to prevent blindness from glaucoma is early detection of glaucoma and treatment.

Not many laymen understand what glaucoma is. The Chinese phrase for glaucoma is ‘qing guang yan’. When translated into English, it means ‘green lights in the eyes’. This certainly adds to the confusion!

Anatomy of the Eye (figure 1)

To understand glaucoma, it is important to know how the eye functions.

The eyeball is round and it has a protective tough white outer coat called the sclera.

The sclera is covered by a relatively transparent, thin membrane called the conjunctiva. The conjunctiva lines the inside of the eyelids and the outer surface of the eye.

The cornea is the transparent clear structure in the front part of the eye that allows light to enter the eye.

The iris, which is the colored structure behind the cornea and in front of the lens, controls the amount of light entering the eye.

The pupil is the opening in the center of the iris and the size of the pupil is controlled by the contraction or relaxation of the muscles of the iris.

The lens of the eye is like the lens of a camera—it focuses light onto the retina at the back of the eye.

The retina of the eye is like the film of a camera——it is the light sensitive layer at the back of the eye that is responsible for vision.

The optic nerve is the structure of the eye where all the nerve fibers of the retina collect together to carry images to the brain.

The optic disc is the place where all the nerve fibers of the retina gather before leaving the eye.

So what actually is glaucoma?

Glaucoma is not a single disease entity, but refers to a group of eye conditions which share certain common features. Most eye surgeons agree that to make a diagnosis of glaucoma, the following features should be present:

1. Higher than normal eye pressure

2. Evidence of damage to the optic nerve

Change in appearance of the optic nerve which shows damage

Damage to the visual field of the eye which can be demonstrated by performing certain tests on the patient.

1. Higher than normal eye pressure

In the normal eye ball, clear watery fluid (called acqueous humor) is constantly produced and it circulates throughout the anterior chamber of the eye, providing nutrients and removing waste products from the anterior structures of the eye such as the cornea, iris, lens etc. In order to maintain a constant eye pressure, the acqueous humor produced must be drained out at about the same rate as it is produced and the drainage of acqueous occurs at the drainage angle of the anterior chamber (also called the filtration angle). (please refer to Figure 2) The production of acqueous is normally constant and if there is a decrease in the drainage of acqueous humor, there will be a buildup of eye pressure. This will result in glaucoma.

The eyeball, like any structure within the body, exists in a relatively constant environment. The pressure within the eye ball is very important as it determines the amount of blood flow within the eye ball. The normal eye pressure of the eye ranges from 12-21 mm Hg. The mm Hg refers to millimeters of Mercury which is a scale used in the measurement of eye pressure.

The fibers of the optic nerve are most vulnerable to damage from high intraocular pressure—if the eye pressure within the eyeball is very high, it compresses the blood vessels of the optic nerve, reducing the amount of nutrients that are supplied to the optic nerve fibers. Over a prolonged period of time, the nerve fibers of the optic nerve slowly die off due to the reduced blood flow. Conversely, if the eye pressure is very low, the pressure within the blood vessels is not balanced by the external surrounding pressure within the eyeball and this leads to leakage from the blood vessels (due to the unbalanced much higher pressure within the blood vessels). This also causes problems such as macula