Retinitis Pigmentosa

Sad to know that there is still no cure for this blinding condition....


Retinitis pigmentosa
Dr Trisha Macnair
A rare cause of progressive loss of vision.

What is retinitis pigmentosa (RP)?
Retinitis pigmentosa (RP) is the name given to a group of hereditary diseases of the retina - the light-sensitive tissue in the back of the eye. About 25,000 families in the UK are affected.

Symptoms
In RP, the light receptor cells in the retina die off. The rod photoreceptors (which provide black and white vision) are mostly affected but sometimes the genetic disorder affects the cones or colour vision photoreceptors. As the retina slowly degenerates and gradually loses its ability to transmit images to the brain, so there is a progressive loss of vision. Cells from the pigmented layer of the retina migrate into the layer containing nerve cells, causing the typical pattern of black or brown star shapes in the retina that gives the diseases their name.

Symptoms usually become apparent between the ages of ten and 30, although some forms can develop much earlier or much later.

Visual loss may be slow or rapid. Often the first symptom is night blindness. Some people notice that it takes longer and longer for their vision to adapt when they walk from a well lit area into a darker area. This may be followed by a narrowing of peripheral vision that leads to tunnel vision (this may not be noticed at first but may become more obvious if the person plays a sport such as tennis).

In one type of RP the loss of vision begins in the central area (macular dystrophy), interfering with reading and detailed work.

Another common symptom involves seeing flashes of light, often described as small shimmering blinking lights.

RP mostly occurs as an isolated problem but other areas of the body may be affected. For example in 10-30 per cent of cases there may be hearing loss – most of these patients have a condition known as Usher syndrome.

Causes and risk factors
More than 100 different gene mutations that may lead to RP have been described. The condition, and the type, results from inheriting one or two of these abnormal genes.

Of those who inherit the disease, the milder forms are usually autosomal dominant, meaning that if you have the disease you have a 50 per cent chance of passing it on to your children. However, nearly half of those with RP have no family history at all.

Some people have non-genetic RP. This may be induced by a viral infection, but most cases are new mutations.

Treatment and recovery
There's no cure for retinitis pigmentosa and there are, at the moment, no treatments that have been proven to stop the visual degeneration (although a number of treatments are under study including gene therapy). There has been some interest in using anti-oxidant compounds such as certain vitamins but there is no clear evidence that they help and there may even be a risk of harm.

However, in many cases the progression of the disease is slow and good support and visual aids can help people cope with the condition.

Because of the huge number of faulty genes that can cause RP, many of which aren't yet fully identified, screening isn't straightforward. However, antenatal diagnosis is possible in some cases where there's a risk of X-linked and autosomal dominant RP.

This article was last medically reviewed by Dr Trisha Macnair in August 2009.