ACCORDING to the World Health Organization (WHO), there are about 284 million people who are visually impaired worldwide, out of which 39 million are blind, and the rest have low vision.
The shocking fact is that 80% of all visual impairment or blindness can be prevented, treated or cured.
Preventable blindness is defined as blindness, which could be either treated or prevented by known, cost-effective means. Among the common causes of preventable blindness are cataract, trachoma, glaucoma, age-related macula degeneration, diabetic retinopathy, and refractive error.
Although there are many causes of vision impairment, we will address the top causes of blindness, both internationally and locally, which are cataract, glaucoma, diabetic retinopathy, and age-related macula degeneration.
In Malaysia, the leading cause of preventable blindness is cataract. It has been revealed that cataract is responsible for 39% of blindness among Malaysians.
Age-related cataract is the most common cause of cataract and it usually occurs among those aged 60 and above. Vision impairment due to cataract is reversible. Unfortunately, some of the elderly prefer to ignore it although it impairs their vision.
Some have old beliefs such as letting the cataract to "ripen" or mature before treating it. This is a myth. Treat cataracts early so that you can enjoy better vision and improved quality of life instead of waiting for a few years for it to mature. Early treatment tends to have less intra-operative complications.
For the elderly, there is fear and hesitation surrounding the removal of cataract. Many think that it is a painful procedure and has a slow healing process.
However, today, with the advancement of cataract surgery, it has become a day-care procedure. The surgery has become shorter in duration, with minimal incisions, and faster healing.
Symptoms of cataract include:
- Blurring of vision. This is usually gradual in onset. People often see a "hazy" or "smoky" world. Although painless, the poor vision may affect daily activities.
- Glare is another common symptom, especially affecting night vision or vision in bright daylight. This is due to the scattering of light caused by the cloudy lens.
- Reduced colour perception. This may not be too severe to be noticed, but colours will appear more faded as the cataract matures.
Imagine one day your sight has deteriorated to the point that you can't see the person standing next to you. This is glaucoma - a condition of the eye which causes progressive, painless but permanent irreversible damage to the nerve of the eye, the optic nerve, causing blindness.
More often than not, the drainage of the fluid within the eye is impaired. This causes the pressure in the eye to rise, which in turn will damage the optic nerve.
As symptoms are scarce in this disease, this condition often goes undiagnosed until the end stage, where irreversible damage has occurred. Therefore, eye screening, especially for people more than 50 years old, is very important for early detection.
However, among the symptoms which may be present, include dull aching pain in or around the eye(s) in chronic form or sudden eye pain, headache and seeing haloes around lights. In the advanced stage, the person may have tunnel vision.
Another cause of blindness is diabetic retinopathy. Diabetic retinopathy means damage to the nerve of the eye caused by changes in the blood vessels of the retina.
The retina is the light-sensitive tissue at the back of the eye. A healthy retina is necessary for good vision. Changes that occur in diabetic retinopathy can be varied, from leakage of protein from the blood vessels to the formation of abnormal new blood vessels that grow on the surface of the retina. These can bleed and cause sudden loss of vision.
However, the changes in diabetic retinopathy depend on the severity and duration of diabetes. Almost all patients who have had diabetes for more than 30 years will have some diabetic changes in their eyes. The dangerous part is that the patients can be asymptomatic even with the new vessel formation, unless the changes occur at the centre of the retina (the macula) that is involved in focusing. The symptoms in diabetic retinopathy include blurring of vision, seeing floaters or shadows, or sudden loss of vision.
The blood vessel damage from diabetic retinopathy can cause vision loss by:
- Fluid leaking into the centre of the macula, the part of the eye where sharp and clear vision occurs. The fluid makes the macula swell, hence blurring the vision. This condition can occur at any stage of diabetic retinopathy, although it is more likely to occur as the disease progresses. This is the most common cause of blurring of vision in diabetic retinopathy.
- Less oxygen supply to the retina, making the retinal cells unhealthy.
- Fragile, abnormal new blood vessels that can rupture and cause bleeding, either in the retinal layer or into the centre of the eye, causing loss of vision. This normally occurs at the advanced stage of diabetic retinopathy.
Diabetic eye screening is a must for all diabetic patients to prevent blindness. The screening should start at the onset of diabetes for non-insulin dependent diabetes mellitus. For insulin dependent diabetes mellitus, eye screening should start after five years of diagnosis or when the patients reach puberty, whichever comes first.
Tight diabetic control is very important to prevent formation of diabetic retinopathy. Patients should control the associated factors that can worsen the retinopathy, such as hypertension, high cholesterol, and smoking. It is important to note that treatments that are available are not to improve vision but to prevent it from getting worse. Therefore prevention is more important at an early stage.
Age-related macular degeneration
Age-related macular degeneration (AMD) is more common in the elderly and is one of the leading causes of vision loss. It is responsible for 8.7% of all blindness (about three million people) worldwide.
In AMD, there is damage to the central area, the macula, which is responsible for our central vision. There are two forms of AMD, wet and dry. The wet form is distinguished by the development of abnormal new blood vessels deep in the sensory retina, which can leak or bleed, hence the rapid loss of central vision due to damage to the macula. An early symptom of wet AMD is when straight lines appear wavy.
On the other hand, the dry form of AMD is due to the breakdown or thinning of the layer of retinal pigment cells (light-sensitive cells) in the macula. In dry AMD, the loss of central vision occurs gradually. The most common symptom of dry AMD is slightly blurred vision, where patients usually have difficulty recognising faces, or may need more light for reading and other tasks.
The risk factors for AMD is age, smoking, family history, obesity, gender (as it is more common among women than men). Early treatment and routine eye examination is very important, especially after the age of 40.
If detected early, AMD can be treated with laser surgery, photodynamic therapy, or anti-VEGF injection.
For all the above eye diseases, preventive measures are most important. With early detection, the loss of vision in a patient is preventable. Everyone should get a complete and detailed eye examination by a qualified ophthalmologist at least yearly for early detection.