Inherited retinal dystrophies including retinitis pigmentosa

Retinitis pigmentosa (RP) is the most common group of IRD, but there are others that have different names, and which may lead to different patterns of sight loss. The way in which your sight is affected depends on the type of IRD you have. Most IRDs cause progressive and permanent changes that reduce your vision, but these changes usually happen slowly, taking years to develop.

This page contains a summary of our information on IRDs. To read our full information, download our Understanding inherited retinal dystrophies including retinitis pigmentosa booklet, which is accredited by the Royal College of Ophthalmologists:

As RP affects the retinal rod cells first, the first symptom you’ll notice is that you don’t see as well as people without a sight condition in dim light, such as outside at dusk, or at night. This is often called “night blindness”. People without a sight condition can usually fully adapt to dim light in 15 to 30 minutes, but if you have RP, it will either take you much longer or it won’t happen at all. You’ll start having problems seeing things in your peripheral vision. You may miss things to either side of you and you might trip over or bump into things that you would have seen in the past.

As your RP progresses, you’ll gradually lose more of your peripheral sight, leaving a central narrow field of vision, often referred to as having “tunnel vision”. How long your central vision is preserved will depend on the type of RP that you have. This may be into your 50s or beyond. However, advanced RP will often affect your central vision, so that reading or recognising faces becomes difficult.

RP is a progressive condition, which means that your sight will continue to get worse over the years. Often, after your vision has been stable for a while, it can get worse suddenly over a short period of time. This new level of vision may then remain stable for quite some time. However, there may be further changes to your vision in the future. This may mean that you have to keep re-adapting to lower levels of sight. The type of RP that you have can affect how quickly these changes develop.

There are many IRDs, some with similar symptoms to RP and some that are very different. Some IRDs affect the whole retina while others only affect the macula in the central retina. IRDs such as RP are called rod-cone dystrophies because the retinal rod cells are affected more than the retinal cone cells, but the whole retina is ultimately affected. Leber congenital amaurosis (LCA) is the name given to a group of more severe rod-cone dystrophies that lead to greater sight loss in very early childhood, often detected at birth.

Cone-rod dystrophies affect the cones earlier and more severely than the rods so that central vision is affected more than peripheral vision.

Macular dystrophies primarily affect your central vision, usually leaving peripheral vision intact.

Choroidal dystrophies (also known as RPE dystrophies) mainly affect how the rod and cone cells work, but they also affect the choroid and the retinal pigment epithelium (RPE) which both lie underneath the retina. Peripheral vision is affected first with central vision affected later on. Choroideremia and gyrate atrophy are examples of this type of dystrophy.

Some IRDs have specific names and some form part of a syndrome, such as Usher syndrome and Bardet-Biedl syndrome where, in addition to sight loss, other aspects of general health are also affected.

IRDs are hereditary conditions caused by a fault (mutation) in one of the genes involved in maintaining the health of the retina.

You inherit genes from your parents. Your genes give the cells in your body the instructions they need to work well and stay healthy. If a gene has a mutation, there is a fault in their instructions and the cells using those instructions don’t work as they should.

Having an IRD means that the faulty gene involved stops your retinal cells from working correctly and results in these cells eventually failing over time. Researchers have identified many of the genes that are associated with different IRDs, but there are still other genes to discover.

About half of people with an IRD have a relative who also has the condition. The way in which these genes are passed on from one generation to another can tell you who in your family has had the condition, how severely your vision could be affected, and the chances of your children being affected. Genes usually come in pairs. You inherit one gene from each of your parents to make each pair. When you have children, you only pass on one gene to them. You can inherit IRDs in different inheritance patterns:

• Autosomal dominant (AD). An IRD that is passed on with AD inheritance is a condition where only one of the genes in the relevant gene pair needs to have a fault to cause the condition. This gene fault can be inherited from either your mother or your father. Usually, this parent will also have the condition. If you have an IRD that is AD, there is a 50% chance of passing on the faulty gene every time you have a child and for that child to have the condition.
• Autosomal recessive (AR). IRDs that are passed on with AR inheritance require both genes in the relevant pair to be faulty. This means you need to inherit one faulty gene from your mother and the other faulty gene from your father to have the condition. If your parents have one faulty gene and one normal gene, they will only be carriers of the condition and their vision will be unaffected by it. If both parents pass on the gene fault to you, you will inherit the condition and your sight will be affected. Someone who has an IRD that is AR will pass on a faulty gene to all their children. However, if these children also inherit a normal copy of the gene from their other parent, they will only be carriers of the condition.
• X-linked (XL). To have an X-linked IRD, the faulty gene is located on the X chromosome. For a male, who has only one X chromosome in each of his cells, if there is an XL gene fault on this X chromosome, he will have the condition. A female, who has two X chromosomes in each of her cells, may have a faulty gene on one X chromosome but a normal copy of the gene on the other. If the normal copy is enough for her to have no symptoms at all or to be only mildly affected, she is a carrier of the condition, and the inheritance pattern is X-linked and recessive in nature (X-linked recessive or XLR). X-linked IRDs can affect some women more severely but this is very rare. A man with an X-linked IRD will pass on the faulty gene to all his daughters but not to his sons. His daughters are likely to be carriers of the condition, but his sons won’t be affected.

About half of people with an IRD don’t know of any other members of their family with the condition. This may be because their relatives were carriers of the IRD and haven’t shown signs of the condition themselves. Sometimes, a person can have an IRD because the fault in the relevant gene has happened spontaneously by itself after conception, without being directly inherited from their parents. If there is no known relative in your family, it may not be possible to find out how your IRD has been inherited without the help of genetic testing to find out which genes are faulty.

Genetic testing can be carried out to identify the specific faulty gene that is causing your IRD. As your test results can indicate the inheritance pattern, it can help to show how likely it is for other members of your family to have the condition as well as indicating whether you could pass on a faulty gene to your children. It may also be useful in predicting how your vision will change over time and with what speed.

Genetic testing uses a blood test to look at your genes to see if any faults are present. Testing for an IRD is complicated and doesn’t always identify all forms of these conditions as new gene faults are still being discovered. Ask your ophthalmologist or GP to discuss genetic testing with you.

Genetic counselling aims to provide you with the information you need to understand your condition and to enable you to make informed decisions relating to it. Genetic counselling can be invaluable before genetic testing is carried out, to give you an understanding of the implications the results might have. A genetic counsellor can help you understand how a condition is passed on within your family by considering your family tree in detail, as well as offering you guidance and support in making any future decisions relating to your condition; for example, knowing the chances of passing on any condition you have can help if you are thinking about starting a family.

An optometrist (also known as an optician) can examine your retina by looking into your eyes. If you have the early signs of classic RP, there will be tiny but distinctive clumps of dark pigment around your retina. Any changes to your peripheral vision can be detected by a field of vision test. If your optometrist is concerned after your eye examination, they can refer you to an ophthalmologist (hospital eye doctor) for more tests.

There are various tests that can diagnose an IRD. These tests can also monitor how your condition changes over time. Your ophthalmologist may be able to say that you have an IRD when they’ve got the results of these tests, but it may not be possible to know the specific IRD you have and what the long- term effects on your vision will be without genetic testing. Some of the tests you may need to undergo include:

• Examination of the retina at the back of your eye.
• Retinal photographs, optical coherence tomography, and autofluorescence imaging – your retina may be photographed using a special camera. By comparing the photographs taken on different visits, your ophthalmologist might be able to monitor how your condition is changing over time.
• Visual field test which checks how much of your peripheral vision has been affected by an eye condition.
• Colour vision tests.
• Electro-diagnostic tests which can tell your ophthalmologist how well your retina is working. They check how your retina responds electrically to patterns and different lighting conditions. Different tests can be carried out to show the results of your retina’s electrical activity. These test results will indicate which layers of your retina have been affected.

While much progress has been made in the past few years in the understanding of the genes involved in RP and other IRDs, there is currently no cure for these conditions. However, ongoing research funded by sight loss charities is taking place all the time and the types of treatment currently being investigated include:

• Gene therapy. The aim of gene therapy is to introduce normal genetic material to the affected retina which will override the fault in the gene which has caused the IRD. For this to have any chance of success, there must be some retinal cells that are still working. Gene therapy relies on knowing which specific gene is faulty as a different therapy is required for faults in different genes. Gene therapy is ongoing for many IRDs in the hope of finding future treatments. There are different approaches within gene therapy which include gene replacement, gene editing and optogenetics (see below).
• Gene replacement. Where normal genes created by genetic scientists are injected into the retina at the back of the eye and the genetic material is carried into the retinal tissue using a harmless virus, known as a vector. The aim is that the instructions from the normal genes will lead to vision that improves or stops getting worse. The first gene replacement therapy, Luxturna (voretigene neparvovec), has been approved as a treatment for IRDs caused by faults on the RPE65 gene.
• Gene editing. Where scientists “cut out” the faulty section of genetic material within the larger gene and replace it with a normal section instead. This approach to treatment needs further development as it is not yet precise enough to ensure that normal genes are not damaged in the process.
• Optogenetics. Where the aim is to make retinal cells that are not photoreceptors able to respond to light where an IRD is more advanced. Optogenetics is still in the early stages of research.
• Stem cell therapy. Stem cells are cells that have not yet specialised to form a specific tissue in the body. If stem cells could be turned into retinal photoreceptors, it may be possible to replace the cells that have stopped working as a result of an IRD, particularly in the more advanced stages of the condition where more cells have been affected and gene therapy would not be an option. Currently, early phase clinical trials are taking place for stem cell treatments but at the time of writing this information, there are no approved stem cell treatments available for any IRDs.
• Growth factors. Growth factors are chemicals that support cells to grow and repair. Research into the use of growth factors to treat retinal disease has been investigated and is ongoing to see if they may be able to preserve retinal cells for longer. However, there is currently insufficient evidence that growth factors would have any long-term benefit in preserving sight.
• Technology known as artificial vision. There are electronic microchips that have been successfully implanted within the human retina that are able to bypass the damaged retinal photoreceptor cells, stimulating the remaining retinal nerve fibres, which form the optic nerve. If it is also healthy, the optic nerve can conduct a signal to the brain, allowing the person to see patterns of light or outlines of objects. These implants don’t bring your vision back or stop your vision from getting worse and you’d still need the other aids you have, such as your cane or your guide dog. Artificial vision systems are still being investigated and there isn’t a system which is able to be easily implanted which returns high levels of vision. No artificial systems are currently available on the NHS.

It’s completely understandable to be upset when you or a family member are diagnosed with an IRD and it’s normal to find yourself worrying about the future and how you or your relative will cope. We can support you at every step, putting you in touch with the advisors you need from any of our supportive teams – just get in touch with our Sight Loss Advice Service.

Having a progressive IRD means that you’ll eventually lose sight, but there are things you can do to make the most of your remaining vision. This may mean making things bigger or smaller, depending on how your vision is affected. Using brighter lighting or using contrasting colours can make things easier to see. A low vision assessment can explore how to make the most of your sight and your GP, optometrist or ophthalmologist can refer you to your local low vision service for an assessment.

Assistive technology can also help, including in-built software on smart phones and tablets, specific apps and low vision devices, as well as computer software programmes that can be installed. You can find out tips for making the most of your sight by downloading our booklet:

Watch our Living with retinitis pigmentosa stories