Retinitis pigmentosa (RP) is the name given to a group of inherited eye conditions called retinal dystrophies.
A retinal dystrophy such as RP affects the retina at the back of your eye and, over time, stops it from working.
This means that RP causes gradual but permanent changes that reduce your vision.
How much of your vision is lost, how quickly this happens and your age when it begins depends on the type of RP that you have.
The changes in your vision happen over years rather than months, and some people lose more sight than others.
What are the symptoms of RP?
When you have a retinal dystrophy like RP, the rod and cone cells in your eyes gradually stop working.
Depending on the type of RP you have, you may notice your first symptoms in your early childhood or later, between the ages of 10 to 30.
Some people don’t have symptoms until later in life.
In RP, the first symptom you’ll notice is not seeing 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 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 may start having problems with 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 your peripheral sight, leaving a central narrow field of vision, often referred to as having ‘tunnel vision’. You may still have central vision until you’re in your 50s, 60s or older.
However, advanced RP will often affect your central vision and you may find reading or recognising faces difficult.
RP is a progressive condition, which means that your sight will continue to get worse over the years.
Often, changes in sight can happen suddenly over a short period of time. You may then have a certain level of vision 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.
What causes RP?
RP is a hereditary condition caused by a fault in one of the genes involved in maintaining the health of the retina.
In RP, the faulty gene causes your retinal cells to stop working and to eventually die over time.
Researchers have identified many of the genes that cause RP and the faults within them, but there are still other genes to discover.
Genetic testing can be carried out to try to find out if you have a faulty gene that causes RP.
This can either identify the faulty gene that is causing your RP or enable you to find out if you’re carrying a faulty gene that your children may inherit.
Genetic testing uses a blood test to look at your genes to see if they’re faulty.
Testing for RP and other inherited retinal dystrophies is complicated. It doesn’t identify all forms of these conditions as new faulty genes are still being discovered.
Genetic counselling can help you to understand the type of RP you have, how it’s likely to affect you in the future and the risks of passing on the condition to any children you may have.
Genetic counselling is usually advised when you have genetic testing. A genetic counsellor asks about your family tree in detail to try and understand how RP has been inherited in your family.
Having a genetic condition in your family may cause emotional concerns. Talking to a genetic counsellor may help you and your family to discuss the eye condition in your family.
Knowing the chances of passing on any condition you have can help if you are thinking about starting a family.
What tests are used to detect RP?
An optometrist (also known as an optician) can examine your retina to detect RP. 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 RP. These tests can also monitor how your RP changes over time.
Your ophthalmologist may be able to say that you have RP when they’ve got the results of these tests, but it may not be possible to know exactly what type of RP 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, fluorescein angiograms 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 RP 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.
SOURCE: The Royal National Institute of Blind People