What is retinitis pigmentosa?
Retinitis pigmentosa (RP) is one of the most common types of inherited retinal disease. 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 made up of light-sensitive cells. There are two different types of cells – cones and rods.
Rods are good for seeing in the dark and seeing things in your side vision. Cones are the cells that are used for your sharp vision. They are good for seeing things in daylight, colour and fine detail.
When you have RP, rods and cones don’t work the way they are supposed to.
How common is RP?
RP is a type of inherited retinal disease. Altogether, inherited retinal diseases affect around 1 in 4000 people or over 2 million people worldwide. They are the leading cause of blindness in working age adults.
What are the causes?
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. There are many more genes, but they haven’t been discovered yet.
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.
What are the symptoms?
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.
How is RP diagnosed?
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 specific genetic eye counselling through the Ocular Genetics Clinic at the Royal Victorian Eye and Ear Hospital or 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.
What treatment is available?
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.
What research is happening at CERA?
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.
- Principal Investigator Dr Tom Edwards is investigating a gene therapy for a specific inherited retinal disease.
- Professor Alex Hewitt (CERA) and Professor Alice Pébay (University of Melbourne) are using stem cell technology and gene-editing techniques to develop new treatments.
- Dr Raymond Wong is using cell reprogramming and stem cell technologies to understand how to replace lost retinal cells.
- CERA and the University of Melbourne are creating a national clinical database of people with inherited retinal diseases, including RP. The project aims to improve understanding of inherited retinal disease and find patients who are eligible for clinical trials.
- Associate Professor Penny Allen is leading the Bionic Eye Project at CERA. She is testing a bionic eye in people with retinitis pigmentosa.
How can I help?
You can support CERA’s research into RP by:
- making a donation
- volunteering for research or being informed about any upcoming clinical trials
- referring yourself or a patient to the national IRD database.