What are Leber congenital amaurosis and early-onset severe retinal dystrophy?
Leber congenital amaurosis (LCA) and early-onset severe retinal dystrophy (EOSRD) are types of inherited retinal diseases.
Children with LCA have poor vision at birth or in the first few months of life This can vary from person to person and can be quite severe with little to no perception of light.
EOSRD usually appears before the age of five years.
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.
Cones are the cells that are used for your sharp vision. They are good for seeing things in daylight, colour and fine detail. Rods are good for seeing in the dark and seeing things in your side vision.
When you have LCA or EOSRD, rods and cones don’t work the way they are supposed to.
How common are LCA and EOSRD?
LCA and EOSRD are types of inherited retinal disease. Altogether, inherited retinal diseases are the second most common cause of legal blindness in childhood. They are also the leading cause of blindness in working age adults.
Inherited retinal diseases affect around 1 in 4000 people or over 2 million people worldwide.
What are the causes?
LCA and EOSRD are genetic eye conditions.
Genes contain DNA, which is short for ‘deoxyribonucleic acid’. A gene has the instructions on how retinal cells in our body grow and work.
LCA and EOSRD are caused by a change or ‘mistake’ in one or more genes. Therefore, cells in the retina don’t work as they are should, resulting in poor vision.
Around 25 different genes are thought to cause LCA and EOSRD. There are many more genes, but they haven’t been discovered yet.
There is a significant overlap between the genetic causes of LCA and EOSRD.
The way that LCA or EOSRD are passed from generation to generation (inheritance) can be different in families.
You may have LCA or EOSRD and know a family member with the condition. Or you may be the first person in your family to have the condition.
Parents who are closely related (e.g. cousins) may have a higher chance than unrelated parents to both carry the same gene causing LCA or EOSRD.
What are the symptoms?
The degree of vision loss a child has can remain stable over time or it can progressively deteriorate.
Other symptoms can include:
- severe difficulties with night vision
- poor central vision
- involuntary eye movements (nystagmus)
- sensitivity to light
- slow reaction of the pupils
- refractive error (need for glasses).
A common sign of LCA in children is poking, pressing, and rubbing their eyes with a knuckle or finger.
Most children with LCA and EOSRD are otherwise healthy. However some children have kidney, bone, muscular, ear or brain abnormalities as well.
How is LCA and EOSRD diagnosed?
An eye healthcare provider will do various eye tests, photographs and scans of your child’s eyes. This helps to better understand their eye problem. Often you will be asked about your child’s general health and if anyone else in the family might have vision problems.
If you or your child are diagnosed with LCA or EOSRD it can be helpful to speak to a genetic counsellor. This may help you:
- understand what LCA or EOSRD could mean for you and your family
- provide support to help adjust to living with the condition
- talk about whether other or future children are likely to have LCA or EOSRD
- learn about any appropriate research studies or clinical trials.
Sometimes doctors cannot be certain which gene is causing LCA or EOSRD just by looking into the eye. 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 LCA or EOSRD in you or your child. 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 one type of LCA/EOSRD caused by a specific gene.
There are no other approved treatments for other genetic types of LCA/EOSRD and other inherited retinal diseases.
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 vision for you or your child. These include:
- regular eye checks, no matter the level of vision
- orientation and mobility training
- using low vision aids such as magnifiers and closed-circuit televisions
- using technology and applications (apps) on devices
- educational support for students at school or university
- wearing sunglasses
- extra lighting for 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. At the same time, they’re advancing scientific knowledge of the genes that cause these conditions.
- 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 LCA and EOSRD. 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 inherited retinal disease.
How can I help?
You can support CERA’s research into LCA and EOSRD 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.