Age-related macular degeneration (ARMD), also called senile macular degeneration (SMD) is a condition which affects older people; causing problems to arise at the middle areas of vision. This is particularly limiting because the central area (field) of vision is used for the performance of detailed, everyday activities such as reading, driving, sewing, etc.
What is the epidemiology of ARMD?
‘Epidemiology’ simply describes the occurrence of a disease condition among given populations according to age, geographical area and other factors of distribution.
According to the WHO, ARMD ranks third among the global causes of blindness after cataract and glaucoma. Age-related macular degeneration is a leading cause of severe, permanent vision loss among individuals aged 60 years of age, and above. The incidence of this condition is particularly higher among the aged population in more developed/industrialized countries. In ARMD, both eyes are usually affected by the disease. Hence, whatever resulting visual impairment tends to be long-standing and significant.
Which structure of the eye is affected by ARMD?
Just according to its name, ARMD leads to degenerative changes around a structure of the eye known as the macula, also known as the ‘fovea’. The ‘macula’ is the structure which is located at the centre of the retina (the thin, light-sensitive tissue which sends visual messages to the brain). The macula is rich in light-sensitive cells known as ‘Cones’ (because they are shaped as such), which are very sensitive under bright lighting conditions, such as in the daytime, and other fine details like colour. On the other hand, other areas of the retina are rich in light-sensitive cells known as rods (also according to their shape), which are highly sensitive to details under less bright conditions e.g at night.
What causes ARMD?
As its name implies; the ageing processis the major risk factor for development of age-related macular degeneration. Other causes which have been implicated include:
- Long-term use of tobacco
- Colouration of the eyes (individuals with light coloured eyes being at higher risk of disease)
- Exposure to ultraviolet rays of the sun, and;
- Poor nutrition, with high consumption of cholesterol and saturated fats in the diet.
Are there different forms of this disease condition?
Yes, ARMD is of two types: the dry, and the wet forms of ARMD
This form is quite common. About 80% (8 out of 10) of people who have AMD have the dry form. Dry AMD is when parts of the macula get thinner with age. People with this form may have yellowish, round deposits known as ‘drusen’, located around their macula. A few small drusen may not cause changes in vision but as they get bigger and more in number, they can dim or distort one’s vision, especially while reading. As the condition gets worse, the light-sensitive cells in the macula (cones) get thinner and eventually die. Eventually, these may lead to ‘blind spots’ in the center of vision (the visual field) and as these become worse, an affected individual might lose vision at the centre.
Only about 10% of people with ARMD are affected by the wet form. In this condition, abnormal blood vessels grow from underneath the macula and leak blood and fluid into the retina. Vision then becomes distorted such that straight lines look wavy. Blind spots may also develop with loss of central vision. These blood vessels and their bleeding eventually form a scar, leading to permanent loss of central vision. The wet type is the more severe form of the disease.
What are the symptoms of ARMD?
Symptoms of ARMD include;
- Reduced vision.
- Blurry areas, with dark shadows in the center of vision.
- Rarely too, there may be reduced perception of colours.
How is ARMD diagnosed and treated?
If you have any of these above listed symptoms, visit a specialist eye clinic as soon as possible. A comprehensive exam would then be conducted for you, which may include the use of a handheld chart and several imaging techniques used to better assess the state of the macula.
Presently, no obvious cure for ARMD exists. However, individuals with the wet type can be managed using laser therapy to destroy abnormal vessels underneath the macula. Drugs may also be injected into the eye to prevent the formation of new, abnormal vessels.
Supplements may also be prescribed by your doctor to slow down the progression of disease. In advanced stages, low vision aids which are used to magnify objects and make them appear larger can also be used to make the most out of the remaining vision.