Dr Leonard Ang
Medical Director
Senior Consultant Ophthalmologist
Lang Eye Centre
Glaucoma is the leading cause of irreversible blindness in the world, with an estimated 70 million glaucoma sufferers worldwide. Glaucoma is a serious, lifelong eye disease that can lead to vision loss if not controlled. But for most people, glaucoma does not have to lead to blindness because glaucoma is controllable with modern treatment. Although the damage from glaucoma cannot be reversed, it can prevent further vision loss if it is treated.
In Singapore, the incidence of glaucoma is approximately 4 to 5% of the population. It accounts for approximately 25% of registered blindness in Singapore.
It is a result of an increase in the pressure of the eye (intraocular pressure) which causes progressive damage to the optic nerve. The pressure build-up occurs because of an imbalance between the production and drainage of fluid within the eyeball.
Types of glaucoma and risk factors
Glaucoma can be divided into primary open-angle glaucoma and primary angle-closure glaucoma. Primary angle-closure glaucoma is a major cause of irreversible blindness in Asia and many parts of the world. It is a particularly serious problem in East Asia, where it represents the major form of glaucoma. In angle-closure glaucoma, the drainage space between your iris and cornea becomes too narrow and the fluid builds up. Other possible risk factors include age, family history and medical history. Older people are at higher risk of glaucoma. Glaucoma may be inherited, which means that relatives of those with glaucoma have a higher risk.
Glaucoma may also arise as a result of other eye diseases. High myopia (short-sightedness) is a risk factor for glaucoma. Other causes include inflammation of the eyeball, advanced cataract which becomes too swollen, eye surgery and injury to the eye, and long-term steroid use.
What are the symptoms of glaucoma?
Vision loss from glaucoma is usually painless and progressive. Most people with open-angle glaucoma do not have symptoms. Because the initial visual field loss starts off from the periphery, hence those with glaucoma do not notice any symptoms in the early stage. The loss of vision slowly progresses to involve the central visual field at the late stages of the disease.
When more severe damage occurs, the individual may complain of poorer night vision and loss of peripheral vision. By the time one notices a deterioration of vision, there is often already moderate to severe damage of the optic nerve. As most people do not realise that they have glaucoma till there is significant damage to the nerve, hence it has been called the ‘silent thief of sight’.
Glaucoma can also present suddenly with a severe eye pain, redness, and sudden loss of vision. This is known as acute angle-closure glaucoma. This is an eye emergency and if the pressure is not controlled promptly, one may suffer permanent nerve damage within a few days.
Diagnosis and monitoring of glaucoma
The diagnosis of glaucoma is confirmed by seeing an eye care specialist. The assessment and monitoring of glaucoma includes measuring the intraocular pressure, examining the optic nerve head, carrying out a visual field examination and using advanced imaging systems to analyse the nerve fibre layers. This will determine if one has glaucoma and its severity. A thorough eye check is also carried out to exclude other causes of glaucoma.
The visual field examination is a sensitive test to assess one’s peripheral vision as well as central vision. Those with glaucoma have an enlargement of the cup-to-disc ratio and loss of the peripheral visual field. Optical coherence tomography (OCT) is an advanced non-invasive, non-contact imaging modality that provides high-resolution cross-sectional imaging of ocular tissues. The nerve fibre layer around the optic disc can be analysed to determine the extent of glaucoma damage. OCT scans have become a standard tool for diagnosing and monitoring glaucoma. It can pick up very early glaucoma damage or progression before changes to the visual field are detected.
Glaucoma treatment
Early treatment of glaucoma may help to prevent further damage and vision loss. There is no cure for glaucoma but in most cases, it can be successfully controlled with medication or surgical treatment. Those with glaucoma will require long-term follow-up to ensure glaucoma control is adequate.
Those with glaucoma are mostly treated with anti-glaucoma eyedrops alone. Eyedrops are very safe, effective and convenient to use. There are many types of medication that can help with glaucoma control and these are usually used once or twice a day.
Laser treatment for glaucoma
Laser treatment can help certain forms of glaucoma, particularly angle-closure glaucoma. A small opening in the coloured part of the eye (iris) is made using lasers to create a bypass channel for fluid to exit. It is performed as a simple out-patient procedure which only takes a few minutes to complete. This is performed for the eye with the condition as well as the eye without as a preventive measure.
Glaucoma surgery
For those with more advanced glaucoma where medication does not optimally control the disease, surgical treatment may be necessary. Traditional glaucoma surgery is usually in the form of a filtering operation known as a trabeculectomy, where a bypass channel is created to allow fluid to exit the eye thereby reducing the internal eye pressure. For those with previous failed trabeculectomies or those with complex glaucoma conditions, an external tube implant may be performed. These are major operations that are associated with potential risks. Hence, these are usually reserved for those with glaucoma that are not medically controlled.
Minimally invasive glaucoma system
There are now surgical treatments for glaucoma developed to help improve eye pressure control for those with mild to moderate glaucoma. Because of the potential complications associated with standard glaucoma surgery, minimally invasive glaucoma system (MIGS)
is a promising surgical alternative.
Because most of the restriction to fluid drainage from the eye rests in the trabecular meshwork, the insertion of tiny devices into the trabecular meshwork aims to increase the outflow of fluid through the trabecular meshwork. Because these devices are extremely small and the insertion is minimally invasive, there is little damage to the surrounding tissue. MIGS may be used for moderate glaucoma. It may be combined with cataract surgery.
These procedures are less invasive, have a higher safety profile with fewer complications and have a more rapid recovery time compared to traditional surgery. However, with the increase in safety, there is a trade-off in the extent of pressure lowering effect, which is why these are reserved for those mild to moderate glaucoma and are not suitable for those with advanced glaucoma.
Glaucoma follow-up
It is important for those with glaucoma to undergo regular follow-up at the eye doctor clinic. The adequacy of glaucoma control can only be determined by your eye doctor, and regular follow-up is essential in ensuring that the glaucoma control is optimal and in picking up early progression of the disease so that appropriate treatment may be prescribed. Because central vision is affected last, the individual should not rely on how well they can see as a measure of their glaucoma control. The vision loss in glaucoma is irreversible, which is why early detection and treatment are so important in preventing blindness.
In conclusion, glaucoma treatment is now very effective with better and safer medication, and individuals need not go blind from the disease if it is detected and treated early. Therefore, it is advisable to go for eye screening when above 45 years of age to detect the presence of glaucoma or other blinding eye diseases.
