Age-related macular degeneration (AMD) is a progressive eye disease where the macula – the part of the retina responsible for central vision – degenerates.
It is the main cause of blindness in older Australians, with 1 in 7 people over the age of 50 having some form of the disease. And it is estimated AMD will affect around 288 million people worldwide by 2040.
Dr Lisa Nivison-Smith is a vision scientist at UNSW's School of Optometry and Vision Science, where she specialises in macular degeneration with a view to improving early detection, diagnosis and management.
"Macular degeneration considerably impacts independent living as it leads to the loss of your central vision – the vision that you use to drive, to read, to watch television, to see the faces of your loved ones," says Dr Nivison-Smith.
"Often, people with the early stages of the condition don't know they have it. Some may experience changes to their vision such as difficulty seeing in low light or straight lines that seem curving or wavy. But for many it doesn't really affect their vision in its early stages and so they find out during a regular visit to the optometrist or the GP when their retina is examined," says Dr Nivison-Smith.
The retina is the tissue found along the back surface of the eye. It is made up of many layers of cells including photoreceptors, the cells that receive light and convert it to signals that tell your brain that you are seeing something.
"When you look at the macula region of the retina of someone in the early stages of macular degeneration, you can see little lumps – fatty deposits – in the photoreceptor layer," says Dr Nivison-Smith.
"As the disease progresses you can see increased damage to this layer including death of the photoreceptors, and this is what causes permanent loss of central vision."
Types of macular degeneration
There are two main types of macular degeneration: dry (atrophic) and wet (exudative).
"The dry form of macular degeneration is more common, accounting for about 80-90% of cases. It involves geographic atrophy – the death of photoreceptors and other retinal cells in the macula over time – leading to gradual vision loss," explains Dr Nivison-Smith.
"The wet form, though less common, is more severe and involves abnormal blood vessel growth under the retina. These new vessels leak fluid or blood, causing rapid vision loss."
Currently, there is only treatment readily available for the wet version of AMD, in the form of injections that prevent the abnormal blood vessel growth. However, the success of this treatment to preserve vision depends on early detection and a rapid initiation of treatment.
For dry AMD, new treatments are on the horizon, with the TGA recently approving a drug targeted at slowing the rate of geographic atrophy. However, this is not yet widely available to patients, and its long-term success rate and side effects are still unclear.
Can you prevent macular degeneration?
With no cure for macular degeneration, most focus is on early detection and implementing approaches to slow the progression of AMD to vision-threatening stages.
"Macular degeneration is caused by both genetic and lifestyle factors. So, the best thing to do is to get regular eye exams, especially if you are over 65 or have a family history of the disease," says Dr Nivison-Smith.
"There is evidence to show a healthy lifestyle, in particular avoiding things like smoking, can significantly reduce your risk of macular degeneration. Specific dietary supplements, known as the AREDS formula, can also slow macular degeneration down when taken at the right stage of disease. So, looking after yourself and talking to a doctor or optometrist about possible dietary supplements can have a big impact," says Dr Nivison-Smith.
Dr Nivison-Smith and her team are developing methods to better predict the trajectory of macular degeneration in individual cases, in order to develop a more personalised approach to care.
"Right now, we can take high resolution images of the retina and see if a person has the early stages of macular degeneration. But we are not able to easily predict what will happen next. We cannot determine who will progress to the next stage of disease quickly and need timely treatment versus who will remain stable and not need any treatment for many years," says Dr Nivison-Smith.
"My research has analysed thousands of retinal images of eyes with early AMD and found that there are changes occurring in other parts of the retina that are not typically measured for macular degeneration."
These changes differed between those whose disease worsened versus those whose disease did not progress. This suggests these new changes may be a way to identify those at high-risk of progression and give them more targeted management.
Ultimately, anything we can do to better understand the early stages of the disease and slow down its progression will make a big difference to people's quality of life, Dr Nivison-Smith says.
"I'm really passionate about stopping avoidable blindness.
"Australia has an amazing eye care system, so I encourage people to visit their optometrist for regular eye checks, particularly if you are over 65.
"By treating people with macular degeneration at the earliest stage possible we can hold off vision loss for a long period of time."
Key Facts:
With May being Macula Month, UNSW researcher Dr Lisa Nivison-Smith explains what's behind the main cause of blindness in older Australians.
