Retinitis pigmentosa

What is retinitis pigmentosa?

Retinitis pigmentosa (RP) is the most common inherited eye condition. It affects around one in 4,000 people in the UK. With RP, a person’s sight loss usually happens gradually, over many years, and can lead to registered blindness.

Most people with the condition will only have sight loss. Less commonly, RP can occur as part of a broader group of inherited conditions (Ciliopathies) affecting other body parts. Examples include Usher, Bardet-Biedl (BBS) and Alström syndromes and Refsum disease, which all cause RP-like sight loss along with other health conditions.

RP is an inherited retinal dystrophy (IRD), a group of closely related eye conditions that affect the retina, the specialised light-sensitive tissue at the back of the eye. Over 280 genes have been identified, mutations which can lead to an IRD, but there could be more. Each of these genes contains the instructions for making proteins crucial for the retina's health. When they contain a mutation that interferes with the protein’s function, it results in an IRD. These gene mutations can be passed down through families.

• Read more about genetics

What causes retinitis pigmentosa?

Retinitis pigmentosa is caused by the gradual decline and loss of light-sensing cells called photoreceptors in the retina, which are vital for healthy eyesight. Scientists worldwide are studying the function of the genes responsible for retinitis pigmentosa and other IRDs to learn more about the biology behind the condition and uncover potential new treatment strategies.

What are the signs and symptoms of retinitis pigmentosa?

Symptoms of retinitis pigmentosa tend to appear during childhood or early adulthood – but in rare cases, they can start much later. RP is a progressive condition, which means that a person’s sight loss will continue to worsen as they get older.

These changes can happen irregularly, with rapid vision losses over a short period followed by long periods of no further changes before another period of deterioration. It is, therefore, difficult to predict both the severity and how quickly an individual’s sight loss will progress – as this varies widely from person to person, depending on the exact genetic cause of their condition.

Common symptoms of retinitis pigmentosa

• Loss of night vision: One of the earliest symptoms of RP is ‘night blindness’, which can affect a person’s ability to see in dim light. It usually starts in childhood – parents may notice their child has issues moving around in the dark. They may also find it takes them longer to adjust to low light levels, a process termed dark adaptation.
• Loss of side (peripheral) vision: As the condition progresses, a person may gradually start experiencing problems seeing things to their sides. This may cause them to start tripping over or bumping into objects below (like kerbs or bollards) or around them (like doors or furniture), which they would have previously seen.
• Tunnel vision: A person’s field of vision will gradually continue to narrow as they lose more of their peripheral sight. Eventually, they will be left with a central narrow field of vision (also called ‘tunnel vision’).
• Difficulty seeing fine detail: How long a person’s detailed, straight-ahead (central) vision is preserved will depend on the type of RP they have. People may keep their central vision into their 50s or older. But those with advanced RP often experience problems with their central vision, which can severely affect their ability to carry out everyday activities like reading or recognising faces.
• Changes to colour vision: Some people with RP may experience difficulties seeing different colours.
  Sensitivity to bright light: A person may find dealing with glare from bright lights and sunlight more challenging.

How is retinitis pigmentosa diagnosed?

An optometrist (or optician) will examine the back of a person’s eye, using a special instrument, to look for signs of RP. They may carry out a field of vision test to assess if a person has any changes to their peripheral vision. If they have any concerns, they may refer the person to an ophthalmologist (hospital eye doctor) for more tests.

Tests for diagnosing retinitis pigmentosa

Some of the tests a person with suspected RP may undergo at the hospital include:

• Optical coherence tomography (OCT): This imaging test takes highly detailed pictures of the retina to examine the fine structure of photoreceptors and look for signs of damage.
• Autofluorescence imaging: This produces an image of the retina in blue light and is very sensitive for picking up RP changes
• Visual field test: This test involves flashing a series of lights to see which ones a patient can or can’t see and builds up a picture of the patient’s field.
• Colour vision tests: These tests will assess a person’s ability to see different colours.
• Electroretinogram (ERG): This test measures the retina's electrical activity or how well it responds to light. The results will tell the ophthalmologist how different layers of the retina are working and, therefore, which one is affected.
• Genetic testing: This involves taking a blood or saliva sample to examine a person’s DNA to see if the gene mutation can be detected. The results can help to confirm a diagnosis of retinitis pigmentosa and may help to predict how their symptoms may change over time. A person whose gene change is known will be better positioned to understand which emerging treatment approaches and clinical trials they may be eligible for. It can also provide information about the inheritance pattern of the condition and risks to other family members.

How is retinitis pigmentosa treated?

Unfortunately, there is currently no known cure or effective treatment that can stop the progression of RP. However, the development of gene replacement therapies and other potential new treatments offer hope for patients in the future.

Some people with retinitis pigmentosa will develop cataracts – and in these cases, cataract surgery may help improve their sight. Others can develop a swelling at the back of the eye, termed cystoid macula oedema, which can be treated with drops or tablets.

A person with advanced RP may benefit from a low vision assessment to evaluate their needs – such as low-vision aids to help maximise their remaining sight and assistive technologies like text-to-speech computer programmes.

What research is underway into retinitis pigmentosa?

There is much ongoing research into finding the remaining genes that cause retinitis pigmentosa, how genetic changes cause damage to the photoreceptors and developing new treatments that can slow down or reverse sight loss.

Think you have retinitis pigmentosa? Here's what to do.

If someone in your family is affected by RP, you can access genetic testing and support from a genetic counsellor. As well as helping you make informed medical and personal decisions, a genetic diagnosis will also provide up-to-date information about potentially suitable new treatments in development.

Have your eyes tested every two years, even if you think your vision is fine. An eye test can spot some eye conditions; if caught early, treatment may prevent further deterioration.

Last updated February 2023
Approved by Dr Roly Megaw, University of Edinburgh