Dr Leonard Ang
Medical Director
Senior Consultant Ophthalmologist
Lang Eye Centre
Millions of people around the world go blind from eye disease every year. Sight is so important yet, many people take it for granted until it is lost. Blindness is one of life’s greatest tragedies. There can be much suffering, anguish and pain living in darkness for the rest of our lives, not to mention the devastating loss of independence and self-esteem.
The leading causes of blindness in the world are cataract, glaucoma, age-related macular degeneration, diabetic retinopathy and cornea diseases. In Singapore, about 0.3% to 0.7% of people are blind, with 2.6% blind in 1 eye and 0.4% blind in both eyes.
We are going to discuss more about some of these conditions below:
Age-related macular degeneration
Age-related macular degeneration (AMD) is a chronic irreversible eye condition that results from damage to the central retina (macula), resulting in loss of central vision. AMD is one of the leading causes of irreversible severe vision loss in individuals over the age of 50. In Singapore, it affects about 7% of the population aged above 40 years old. Smokers and those with cardiovascular diseases are more prone to developing AMD.
The macula is progressively damaged as a result of age-related changes that present in 2 major forms:
Dry or Non-Exudative AMD
The dry form of AMD is associated with yellow deposits, called drusen over the macula, as well as progressive thinning and degeneration of the macula. The condition may be silent with little visual symptoms initially. As it progresses, there may be progressive blurring and distortion of the central vision.
Wet or Exudative AMD
This makes up 10% of AMD cases and may cause devastating vision loss. It results from the development of abnormal leaky vessels or a membrane beneath the retinal layer. These abnormal vessels may bleed or leak fluid, proteins or fats.
In wet AMD, there may be a sudden dramatic loss of vision. There may also be distortion of vision or a shadow over the central vision. The vision loss may be profound.
There is no proven treatment for dry AMD. Certain lifestyle modifications such as stopping smoking may help reduce progression of the disease. The use of low vision aids may also help in the visual rehabilitation of patients.
For wet AMD, there are treatments to slow or stop the progression of the disease by stopping abnormal blood vessel growth. This includes the use of medication such as Eylea (aflibercept), Lucentis (ranibizumab) or Avastin (bevacizumab). These medications work by inhibiting proteins called vascular endothelial growth factor (VEGF), which stimulate the growth of new blood vessels in the body.
These may be combined with laser treatment to seal off the abnormal vessels and prevent leakage of fluid from these vessels. These treatments may help to slow down the progression of the disease and prevent further vision loss.
Reducing smoking, blood cholesterol, controlling high blood pressure and cardiovascular risk factors, and a healthy diet of green leafy vegetables and coloured fruits can help to reduce the progression of AMD. Lutein, nutrients such as beta carotene (Vitamin A) and various Vitamins C and E have also been shown to prevent or slow the progression of AMD.
Cornea disease
The cornea is the central clear transparent window of the eye. Corneal blindness is one of the leading causes of treatable blindness in the world, with more than 20 million cases globally.
Various diseases can affect the cornea and cause visual impairment. They include:
- Cornea scarring and haze from infection and injury.
- Cornea infection such as viral or bacterial infection. A common cause of bacterial infection is contact lens-related infection which can be potentially serious.
- Cornea inflammation, which may result in melting or thinning of the cornea
- Swelling and cloudiness of the cornea due to damage or ageing of the innermost layer of cells of the cornea (known as the corneal endothelial layer)
- Hereditary conditions that may affect the shape of the cornea (keratoconus), or have opacities that block vision (dystrophies)
Those with cornea infection and inflammation may experience eye pain, redness, tearing and loss of vision. If the disease is not well treated or is more chronic, this often results in permanent scarring or haziness of the cornea which may cause a permanent impairment of vision.
For cornea infection or inflammation, these may be treated with medication, such as antibiotics or anti-inflammatory eye drops. For more severe cases that are not treatable with medication or in cases where the cornea becomes scarred or hazy, surgery in the form of cornea transplantation may be required to restore vision.
Cornea transplantation is the most frequently performed transplant procedure and it is the most successful solid organ transplant. When all the layers of the cornea are involved, a full thickness corneal transplant is performed (Penetrating Keratoplasty) (Figure 8).
Recent advances in cornea transplantation enable us to replace the specific part of the cornea that is diseased, when the disease has not extended to the all the layers of the cornea. This form of targeted cornea replacement is known as a Lamellar Keratoplasty. This improves our ability to treat many corneal diseases more effectively. This has led to better visual outcomes, lower graft rejection risk and longer graft survival following corneal transplantation. These advances in cornea transplantation surgery have improved our ability to treat many corneal diseases more safely and effectively.
Conclusion
About 80% of blindness is preventable if the eye disease is detected and treated early. Early detection and treatment of cataract, glaucoma, diabetic retinopathy and other eye diseases is the key to preventing blindness. Because man of the common blinding conditions start off with minimal symptoms and gradually cause visual loss, many patients do not realise they have eye disease till it is more severe.
Eye disease treatment is very advanced now, with safer and more effective treatments. As such, patients should not wait for their eyes to be severely affected before seeking treatment. It is therefore wise to undergo an eye screening with an eye specialist for those above 45 years of age. This can help to pick up diseases in the early stage so that treatment can be instituted earlier to prevent visual loss.
