The retina is the layer at the back of the eye, which captures the light, like the film in a camera. The small central area of the retina is called the macula. The centre of the macula is the fovea. It is the highly sensitive area that produces the finely detailed colour images that make up the centre of your vision. The macula is important for driving, reading, recognition of faces, and similar tasks.
Macula degeneration occurs when the macula becomes damaged. When the normal function of the macula is disrupted, sight in the centre of the field of vision is affected.
Macula degeneration usually affects both eyes, but it may affect one eye before the other. If macula degeneration continues, severe visual impairment can result, resulting in “legal” blindness.
Visual loss is restricted to the central part of the vision. Peripheral vision usually remains normal, so patients never go “black blind” from macula degeneration.
Although there are many causes of macula degeneration, the most common form is related to age, when it is referred to as “age-related” macula degeneration (ARMD). AMD occurs in people as young as 50.
ARMD is common. About 15% of people older than 50 have early macula aging, but only 2% become severely affected. Over the age of 75, 30% have early signs, and 10% become severely affected. As people are living longer, ARMD has become a significant problem.
There are two basic types of Age-related macula degeneration. They are commonly called "Dry", and "Wet".
1. Dry ARMD, also called, non-exudative ARMD. This describes the slow aging process that "rots" away the macula. It occurs because of failure of the metabolic cells of the macula, called the retinal pigment epithelium. These cells are the most active cells in your body, so aging of these cells leads to failure of the photoreceptors, resulting in loss of vision. In Australia there is no treatment for Dry AMD. In the USA recently, two drugs have been approved for Dry AMD treatment. They require regular injections into the eye. They do not improve the vision, which continues to decline as per the natural history. So it is reasonable to ask why they drugs were approved at all? If and when these drugs become available in Australia, we will consider the longer term before we can recommend them to patients.
2. Wet ARMD, now called "exudative ARMD'. The term exudative means that there are new blood vessels that have developed at the macula, that are leaking fat, blood and water. These blood vessels also cause scarring, that can rapidly destroy the central vision. There is treatment for this type of ARMD, in the form of injections.
Injection treatment has been available in Australia since 2006. There are now five drugs available, called "anti-VEGF" drugs. In order of approval in Australia, they are Avastin, Lucentis, Eylea, Beovu, and Vabysmo. We have studied all these drugs in real-world patients over this time, and there are definite advantages and disadvantages between them, depending on the type of disease present in the eye.
Injections for exudative ARMD are very powerful to prevent loss of eyesight from leaking blood vessels. But they do not stop the progression of the dry component of the ARMD, which slowly progresses with age. Injections are initially given into the eye every 4 weeks for the first 3-6 months, until the disease stabilises. We then increase the treatment interval between injections. This is called the "inject-and-extend" treatment regimen. This gives the patient the greatest treatment benefit with the least number of injections.
Most patients requiring injections will need the injections to be repeated indefinitely. Only occasionally can we stop the injections. Most patients can be controlled with an injection every 8-12 weeks, depending on the aggression of the disease.
Presentation and initiation of treatment for exudative or wet ARMD is "URGENT". Most visual loss is preventable and treatable, so patients should not delay presenting if they have any pain or new reduced vision.