There are not many factors that can help identify someone at risk of developing age-related macular degeneration (AMD), and even fewer that can be modified.

Age and family history are the biggest risk factors by far, but apart from stopping smoking there is not much that a person can do to reduce their personal risk of developing the disease.

Discovering new risk factors, especially those that can be changed, has the potential to implement new strategies to intervene and prevent vision loss.

The search has led CERA Deputy Director and Head of the Macular Research Unit Professor Robyn Guymer AM to look at sleep apnoea, an often undiagnosed condition that is believed to affect as many as a quarter of Australians over 65 years of age.

“Sleep apnoea is a very common, often undetected problem in our community, and it’s common in the same group of people who develop age-related macular degeneration,” says Professor Guymer.

“We don’t currently ask questions in our eye clinics about sleep apnoea, which seemed like a missed opportunity.”

Professor Guymer says the two conditions may have a physiological link.

In sleep apnoea, the throat muscles relax which obstructs airflow and reduces the amount of oxygen the body is able to absorb during the night.

As oxygen plays a key role in the restorative process the retina goes through overnight, sleep apnoea could accelerate the progress of AMD.

“If we are able to find an association between having sleep apnoea and AMD then currently available treatments for sleep apnoea, such as continuous positive airway pressure (CPAP), may be a potential treatment,” says Professor Guymer.

“This is opposed to having to develop a new drug, for example, which takes years to develop.”

Looking for a link

Research by Professor Guymer, with medical student Wendy Fang and visiting researcher Dr Palaniraj Rama Raj, has already uncovered some early indications of a link based on the results of patient surveys.

While the very early findings are promising, more work needs to be done to confirm the association.

“While we’ve asked several hundred people the validated questionnaires, the questions themselves are not perfect for detecting those likely to have sleep apnoea,” says Professor Guymer.

Her team is now working on more objective ways to determine if there is an association between those who actually do drop their oxygen levels at night and AMD.

Researchers in the Macular Research Unit are now providing patients with pulse oximeters to take home and wear over several nights to record actual oxygen levels in their blood.

“We record the number of times the oxygen levels drop below a normal level during sleep and how low it drops,” says Professor Guymer.

Future work will also include looking to see if the association is with all AMD or particular subsets, such as the critical phenotype of reticular pseudodrusen (RPD).

“We’re trying to understand the core problem of RPD, a particular deposit that occurs in only about a quarter of people with AMD but is highly prevalent in the late form of disease when vision loss occurs,” says Professor Guymer.

“If there were some more evidence to support an association, the next step might be to do formal sleep studies to consolidate the screening tests.”

Professor Guymer’s work on sleep apnoea and AMD is supported by funding from of the National Medical Health and Research Council’s Synergy Grants Program.

These grants are designed to fund programs that aim to solve problems which cannot be solved by an individual researcher or a single group.

This particular grant has brought together the researchers from CERA, WEHI and the University of Melbourne.