Inherited retinal diseases (IRDs) are also called inherited retinal degenerations or inherited retinal dystrophies. They are the most common cause of legal blindness in working-aged Australians, and the second most common cause in children. We estimate there are around 19,000 Australians living with IRD and, as they are genetic, they can affect multiple people in the same family.

The retina is the light-sensitive tissue at the back of the eye, which contains different types of retinal cells. When you have an IRD, the retinal cells don’t work the way they are supposed to. In particular, the cells that react to light become damaged and die over time, leading to vision loss.

In most people, IRDs only affect the eyes. However, some types of IRDs are linked with other health issues and are called ‘syndromic IRDs’. The most common syndromic IRD is Usher syndrome, which affects vision, hearing and balance in childhood.

There are many types of IRDs. They affect different retinal cells. Some of these include:

• Retinitis pigmentosa (RP)
• Rod dystrophy or rod-cone dystrophy
• Cone dystrophy or cone-rod distrophy
• Usher syndrome (USH)
• Bietti crystalline dystrophy (BCD)
• Batten disease
• Bardet-Biedl syndrome (BBS)
• Alport syndrome
• Leber congenital amaurosis (LCA) or early onset retinal dystrophy (EORD)
• Achromatopsia
• Congenital stationary night blindness (CSNB)
• Macula dystrophy
• Stargardt’s disease
• Best disease
• Pattern dystrophy
• Sorsby fundus dystrophy
• Doyne’s honeycomb dystrophy
• Choroideremia
• X-linked retinoschisis (XLRS)

IRDs are genetic conditions.

Genes contain DNA, which is short for ‘deoxyribonucleic acid’. A gene has the instructions on how retina cells in our body grow and work.

IRDs are caused by a change or ‘mistake’ in one or more genes. Therefore, cells in the retina don’t work as they are supposed to and over time you lose vision.

Currently there are around 300 genes known to cause IRD.

The way that each IRD is passed from generation to generation (inheritance) can be different in families.

You may have an IRD and know a family member with the condition. Or you may be the first person in your family to have an IRD.

IRDs are the leading cause of blindness in working age adults in developed countries, such as Australia and the UK. Altogether, they affect around 1 in 4000 people, which is equivalent to over 2 million people worldwide.

Symptoms depend on the type of IRD and the individual.

Some symptoms might be:

• finding it hard to see in dim or dark settings
• reduced side vision – bumping into objects or people
• glare and difficulty in bright light
• reduced central vision making it hard to read, recognise faces or watch TV
• not seeing all the colours or differences between certain colours.

Vision changes are often gradual, not sudden.

Some people lose more vision than others. This can happen even between family members with the same condition.

An eye healthcare provider will do various eye tests, photographs and scans of your eyes. This helps better understand your eye problem. Often you will be asked about your general health and if anyone else in the family might have vision problems.

Your doctor may recommend you visit a genetic eye clinic for genetic counselling. This may help you:

• understand what the condition could mean for you
• provide support to help you adjust to living with or being at risk of developing the condition
• talk about whether children or family members are likely to develop the condition
• if you are thinking about starting a family
• learn about any appropriate research studies or clinical trials.

Doctors cannot be certain which gene is causing the IRD just by looking into the eye. Hence, genetic testing may be suggested. This involves having a small blood or saliva sample collected and sent to a laboratory. Genetic testing can give an answer in about 6 out of 10 cases, but often additional testing is required.

In Victoria, you can access genetic testing through the Ocular Genetics Clinic at the Royal Victorian Eye and Ear Hospital or the Genetic Eye Clinic at The Royal Children’s Hospital. If you live in another state, it is best to speak with your eye healthcare provider and local clinical genetic service.

In some research studies led by CERA, we can also offer genetic testing and counselling.

Currently, there is one approved gene therapy for a very rare IRD caused by a specific gene (Leber Congenital Amaurosis due to biallelic RPE65 gene mutations).

But for most IRDs, there is current medicine or surgery to prevent or cure vision loss.

There is a lot of promising research into gene therapy, stem cell technology and other medicines that may help people with IRDs. Through our clinical trials partner, Cerulea, we run many of these industry-sponsored clinical trials and are also developing our own potential therapies.

There are steps you can take to look after and maximise your vision. These include:

• regular eye checks, no matter the level of your vision
• orientation and mobility training
• using low vision aids such as magnifiers and closed-circuit televisions
• using technology and applications (apps) on your devices
• educational support for students at school or university
• wearing sunglasses
• extra lighting if you need help in dark environments
• not smoking
• having a healthy diet.

You may find support groups and online patient communities helpful.

You can find further information and support at Vision Australia, Guide Dogs Australia and Retina Australia.

CERA researchers are working on potential treatments for inherited retinal diseases (IRDs). At the same time, they’re advancing scientific knowledge of the genes that cause IRD and the impacts these conditions can have on everyday life.

A few key projects include:

• We have a large research program in Usher Syndrome, working closely with community partners (UsherKids Australia and Silent Sight) and colleagues in the Vision Science Innovation Alliance to accelerate development of treatments for this paediatric-onset syndromic IRD.
• Dr Raymond Wong is using cell reprogramming and stem cell technologies to understand how to replace lost retinal cells, and is leading a CERA startup company called Mirugen.
• Principal Investigator Dr Tom Edwards leads several IRD trials and is developing new therapies in his laboratory.
• Dr Edwards and Prof Lauren Ayton run the VENTURE IRD registry, which has data on over 550 people with IRDs so far.
• Professor Alex Hewitt (CERA) and Professor Alice Pébay (University of Melbourne) are using stem cell technology and gene-editing techniques to develop new treatments.
• Associate Professor Penny Allen is leading the Bionic Eye Project at CERA, which has provided a retinal prosthesis to 7 Victorians to date.