Retinitis pigmentosa (RP) is one of the most common types of inherited retinal disease (IRD). It is also called rod dystrophy or rod-cone dystrophy.

For normal vision, the retina acts like the film in a traditional camera. It is here where the pictures are created, then sent to the brain for interpretation.

The retina is the light-sensitive tissue at the back of the eye, which contains different types of retinal cells. When you have RP, 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.

RP is a type of inherited retinal disease (IRD). Altogether, IRDs affect around 1 in 4000 people or over 2 million people worldwide. They are the leading cause of blindness in working age adults.

RP is a genetic condition.

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

RP is 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.

Around 70 genes are known to cause different types of RP.

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

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

Parents who are closely related (e.g. cousins) may have a higher chance than unrelated parents to both carry the same gene causing RP.

The first symptoms of RP are usually loss of side vision and difficulty seeing in dim light.

Other symptoms may include:

• finding it hard to judge changes in levels, such as steps and gutters, when walking
• glare and difficulty in bright light
• reduced vision when looking straight ahead (in advanced cases).

In RP, vision gets worse over time. Some people lose more vision than others. This can happen even between family members with the same condition.

In most people, RP only affects the eyes. But some types of RP can be linked with other health issues, like Usher syndrome which causes hearing and vision loss.

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 RP 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 RP
• if you are thinking about starting a family
• learn about any appropriate research studies or clinical trials.

Sometimes doctors cannot be certain which gene is causing RP just by looking into the eye. During your appointment genetic testing may be suggested. This involves having a small blood or saliva sample collected and sent to a laboratory.

Genetic testing could help find out the exact gene causing your type of RP. However, it doesn’t always identify the gene because many genes are still being discovered.

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.

Currently, there may be a possible treatment for a very rare inherited retinal disease caused by a specific gene.

But for most inherited retinal diseases, there is no potential medicine, surgery or ability to cure vision loss.

There is a lot of promising research into gene therapy and stem cell technology and upcoming clinical trials that are bringing hope to families.

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 like RP. At the same time, they’re advancing scientific knowledge of the genes that cause these diseases.

Current research includes:

• We have a large research program in Usher Syndrome, working closely with community partners (UsherKids Australia and Silent Sight Foundation) and colleagues in the Vision Science Innovation Alliance (VSIA) to accelerate development of treatments for this paediatric-onset syndromic IRD.
• Professor 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 Professor 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 seven Victorians to date.