Retinitis Pigmentosa

What is retinitis pigmentosa?

Retinitis pigmentosa (RP) is the most common inherited eye condition. It is a form of inherited retinal dystrophy (IRD), which is a group of closely related eye conditions that affect the retina, the specialised light-sensitive tissue at the back of the eye.

RP causes sight loss that happens gradually, over many years, and can lead to registered blindness.

What causes retinitis pigmentosa?

Retinitis pigmentosa is caused by the gradual decline and loss of light-sensing cells called photoreceptors in the retina.

Scientists worldwide are studying the function of the genes responsible for retinitis pigmentosa and other forms of inherited retinal dystrophy (IRD) to learn more about the biology behind the condition and uncover potential new treatment strategies.

Over 280 genes have been identified, mutations of 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.

Less commonly RP can occur as part of a broader inherited syndrome that affects other parts of the body. Examples include Usher, Bardet-Biedl (BBS) and Alström syndromes and Refsum disease, which all cause RP-like sight loss along with other health conditions.

What are the signs and symptoms of retinitis pigmentosa?

The main signs of retinitis pigmentosa are gradual loss of ability to see in dim light and around the edges of your vision. Symptoms tend to appear during childhood or early adulthood, but in rare cases, they can start much later. 

Common symptoms of RP include: 

Loss of night vision: One of the earliest symptoms of RP is ‘night blindness’, which can affect your 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.

Loss of peripheral vision: As the condition progresses, you may gradually start experiencing problems seeing things to the side or below your line of vision. This may cause tripping over or bumping into objects like kerbs, bollards, doors or furniture.

Tunnel vision: Your field of vision will gradually continue to narrow as you lose more of their peripheral sight. Eventually, this leaves a central narrow field of vision (also called ‘tunnel vision’).

Difficulty seeing fine detail: How long your detailed, straight-ahead (central) vision is preserved will depend on the type of RP you have. Some people keep their central vision into their 50s or older. People 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: You may find dealing with glare from bright lights and sunlight more challenging.

Is retinitis pigmentosa serious?

Retinitis pigmentosa leads to progressive sight loss and sometimes eventual blindness. It is 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.

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.

How is retinitis pigmentosa diagnosed?

To look for signs of RP, an optometrist (or optician) will examine the back of your eye, using a special instrument. 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.

If it's suspected you may have RP, some of the tests you undergo at the hospital may 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.

What are the treatments for retinitis pigmentosa?

Unfortunately, there is currently no known cure or effective treatment that can stop the progression of retinitis pigmentosa. However, the development of gene replacement therapies and other potential new treatments offers hope for people with this condiiton in the future. 

Some people with RP 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, called cystoid macula oedema, which can be treated with drops or tablets.

Someone 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 can help retinitis pigmentosa?

If you have RP, genetic testing can show which gene change has caused the condition, which can provide information about the inheritance pattern and risks to other family members. Knowing your gene change can be helpful in understanding which emerging treatment approaches and clinical trials you may be eligible for.

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.

What research is there 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. 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.

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