For many visitors to the zoo, the differences between a lizard and a salamander might be very hard to spot: both have long bodies, stretched tails and crawl among plants on their four legs.

However, a trained eye would notice that lizards have scales while salamanders have smooth skin and stumpy toes.

Doctors go through a similar process when diagnosing disease.

For some eye diseases the signs are easy to spot, but for others the signs are so subtle that getting the correct diagnosis can be hard.

Dr Ceecee Britten-Jones, CERA Honorary Research Fellow and Postdoctoral Research Fellow at the University of Melbourne, is working on improving the diagnosis between atrophic age-related macular degeneration (AMD), also known as dry AMD, and inherited macular dystrophies.

With new treatments on the horizon, faster and more accurate diagnosis is more important than ever.

“It’s important that all patients with macular diseases first get the correct diagnosis, so they don’t miss opportunities for clinical trials and can also receive the right treatment for their condition,” she says.

Spot the difference

It can be easy to misdiagnose macular dystrophies as AMD because they both affect the macula and eventually lead to loss of central vision – but that’s where the similarities end.

“On examination, these two diseases can appear very similar, but genetically they are very different,” says Dr Britten-Jones.

While the underlying causes of AMD are not yet known, both genetic and lifestyle factors seem to play a role.

In contrast, macular dystrophies are a group of inherited retinal diseases (IRDs), which includes Stargardt’s disease, and are caused by changes or ‘mistakes’ in a single gene.

Genetic testing is the only way to get an absolute confirmed diagnosis of a macular dystrophy.

As genetic testing is not easily accessible and interpreting the results can be challenging, it’s important the testing is only done on people who don’t have a clear‑cut diagnosis.

By looking more closely at the differences between macular diseases, Dr Britten‑Jones and her team aim to help clinicians better understand which patients should be referred for targeted genetic testing.

Joining forces

Before Dr Britten-Jones and her team can help clinicians diagnose these similar yet genetically different diseases, they need to find people in the community who may have been misdiagnosed.

Study participants have already been referred through the Macular Research Unit, led by Professor Robyn Guymer AM.

“Some participants may have first been referred to macular research with AMD,” says Dr Britten-Jones.

“After examination, if Professor Guymer believes they may instead have a macular dystrophy, these participants will then be referred to the study.”

Dr Britten-Jones is also collaborating with CERA Honorary Researcher Associate Professor Heather Mack AM, who is reviewing patients diagnosed with AMD from private ophthalmology clinics.

“By looking at both research and real-world settings, this study will help us obtain a broader and more accurate representation of potential misdiagnosis,” says Associate Professor Mack.

Improving treatment access

Once they have identified potentially eligible participants, Dr Britten-Jones and her team will investigate the genetic changes that are known to be associated with both types of macular diseases.

After the genetic diagnosis is made, they will then look for distinguishing features that can set the macular diseases apart.

“We want to help other clinicians to better diagnose macular diseases, so that the right patients can be referred for targeted genetic testing,” says Dr Britten-Jones.

“Our goal is for every patient with macular diseases to eventually get the right treatment for their condition.”

This article first appeared in Visionary magazine – Spring 2023.