What are inherited retinal diseases?
Inherited retinal diseases (IRDs) are also called inherited retinal degenerations or inherited retinal 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. It contains different types of retinal cells. When you have an IRD, the retinal cells don’t work the way they are supposed to. Over time you may lose vision.
In most people, IRDs only affect the eyes. However, some types of IRDs are linked with other health issues.
What are examples of IRDs?
There are many types of IRDs. They affect different retinal cells. Some of these include:
- Retinitis pigmentosa (RP)
- Rod dystrophy or rod-cone dystrophy
- 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)
- Cone dystrophy
- Cone-rod dystrophy (CORD)
- Congenital stationary night blindness (CSNB)
- Macula dystrophy
- Stargardt’s disease
- Best disease
- Pattern dystrophy
- Sorsby fundus dystrophy
- Doyne’s honeycomb dystrophy
- X-linked retinoschisis (XLRS)
What are the causes?
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 250 genes known to cause IRD. There are many more genes, but they haven’t been discovered yet.
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. Parents who are closely related (e.g. cousins) may have a higher chance than unrelated parents to both carry the same gene causing an IRD.
How common are IRDs?
IRDs are the leading cause of blindness in working age adults. Altogether, they affect around 1 in 4000 people or over 2 million people worldwide.
What are the symptoms?
Symptoms depend on the type of IRD and the patient.
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.
How is an IRD 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 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.
Sometimes doctors cannot be certain which gene is causing the IRD 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 IRD. 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 IRD caused by a specific gene.
But for most IRDs, 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 IRD research is happening at CERA?
CERA researchers are working on potential treatments for IRD. At the same time, they’re advancing scientific knowledge of the genes that cause IRD.
- Principal Investigator Dr Tom Edwards is investigating a gene therapy for a specific IRD.
- 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 IRD The project aims to improve understanding of IRD 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 IRD 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.