Sisters Kate and Nicole Barrett were born 18 months apart and have always been there for each other.

Retinitis pigmentosa – an inherited retinal disease (IRD) that causes progressive, irreversible vision loss – runs through their relationship.

Kate, 35, was diagnosed at six and told she would be blind by 13. When that didn’t happen, she was told she would be lucky to make it to 20.

As Kate’s sight declined, she earned qualifications in counselling and criminology, wrote children’s history books and had twin girls, Abigail and Aurora.  She now has a small amount of tunnel vision and guide dog ‘Misty’ to help navigate the world.

Nicole, 33, was diagnosed at 17. Despite the initial shock, she went on to develop a successful career in occupational therapy. “I am now at the point where I am looking to start a family. I have been able to achieve the things I have wanted to in my career, I’m happy, I’ve got married and everything is progressing well,’’ she says.

“The most difficult thing is not being able to get a clear prognosis of how the disease will progress. I live from day to day and hope my vision stays the same.”

The sisters are part of a new study between the Centre for Eye Research Australia and the University of Melbourne to learn more about IRDs and identify patients suitable for future trials.

Natural history

Dr Lauren Ayton, who leads the natural history study, says that only five years ago someone diagnosed with an IRD would have been told their disease was untreatable.

But rapid advances in gene and cell therapies mean that treatments to stop vision loss are now being trialled overseas and will soon become available in Australia.

While these treatments could be life changing, researchers don’t yet know all of the patients who could benefit or how to find them.

An additional challenge is that with more than 200 different genes associated with IRDs, each treatment is targeted to specific genes and many people do not have an exact diagnosis.

To overcome this problem the researchers are attempting to identify, assess and track the estimated 16 500 Australians with IRD. As part of the study, people with an IRD will receive a comprehensive eye examination and genetic testing.

“This will enable us to create a database with information about their vision, their genetic profile and whether they are interested in taking part in clinical trials,’’ says Dr Ayton. “As new treatments come up, the patients will be ready to go.’’

The eventual goal is a national register which would list everyone in Australia suitable for an IRD treatment. The research has another important outcome – a better understanding of the sub-types of IRD and how they progress.

Kate and Nicole say new gene therapy research gives them hope that in their lifetime there may be a treatment for retinitis pigmentosa, either to stop vision loss or to slow down the rate of loss.

“Even if I don’t have the exact genes for the treatments that are being tested (for) now, I hope there will be something in the future,’’ says Nicole.

“It gives everybody hope to know that people are looking into all avenues and looking for a cure.”

Kate’s wish is simple: “I hope that my sight can stay where it is so I can see my daughters graduate and get married. That would be irreplaceable.’’

For more information or to express interest in getting involved in this study, please contact the research team at IRD@groups.unimelb.edu.au