Retinitis pigmentosa (RP)

Retinitis pigmentosa (RP)

What is RP?

Retinitis pigmentosa (commonly referred to as RP) is a progressive group of inherited eye diseases which are characterised by degeneration of the photosensitive cells in the retina of the eye which perceive light and colour. These cells are called the rods and cones.

RP is a major cause of blindness in people under the age of 60, and affects millions of people worldwide.

What causes it?

As of yet, the cause of retinitis pigmentosa has not been found, but research into the disease is ongoing. There appears to be a genetic component, as the condition tends to run in families. Many of the genes involved in RP have been identified, the first of which, called rhodopsin, was discovered by researchers in the Ocular Genetics Laboratory in Trinity College Dublin. Although genetic, there are some cases of sporadic RP where it has not ben seen previously in families.

What are the symptoms?

The onset of RP may begin in childhood, but may not detected for many years. The disease usually begins in the rods, which are responsible for peripheral (side) and night vision. If left unchecked, the patient will be left with tunnel vision and will just be able to see what is straight ahead.

Among the symptoms of RP are:

  • Difficulty seeing in places which are dimly lit, or difficulty seeing in the dark.
  • Loss of ability to make out colours.
  • Decreased central vision.
  • Loss of peripheral (side) vision.

How is it diagnosed?

People at risk from retinitis pigmentosa can be given an eye examination called an ERG (electroretinogram). During this procedure, the eye response to a light stimulus is recorded. If RP is present, the ERG will show decreased signals from the rods and cones, but particularly from the rods.

How is it treated?

There is no treatment for retinitis pigmentosa, and no way to halt its progression either. The sad fact of the matter is that many people who suffer from RP will be legally blind by the time they are 40 years old, even though they may still have enough vision to walk unaided. However, they will be unable to drive a car, operate machinery or read for long periods due to the deterioration in their peripheral vision.

There is a lot of research into RP both in Ireland and worldwide. Researchers at University College Cork are examining why the cells of the retina are dying prematurely. At UCD, researchers are looking at events at the blood retinal barrier. In the National Microelectronics Research Centre (NMRC) in Cork, the team is working to create an 'artificial eye' - a microchip to be inserted beneath the retina which would replace the function of the dying cells.

Can RP be prevented?

There is no way to prevent retinitis pigmentosa. For some forms of the disease, however, the gene which causes it has been identified. Where there is a history of RP in families, or where one person in a relationship suffers from the disease, genetic counselling should be sought in order to assess the risk factors of children inheriting the disease.

It is thought that Vitamin A supplements in certain forms may delay the symptoms of PR. It is also very important to protect eyes from blue light which is more damaging to the eye than UV rays and can cause glare which can be very uncomfortable to individuals with RP. Corning blue-block glasses are available from some opticians.

What is the prognosis?

Unfortunately, the prognosis for people suffering from RP is not very positive. The vast majority of people who contract the disease will end up losing most of their vision, and will be classified as legally blind even though they may retain sufficient vision to enable them to see straight ahead.

However, much research is being carried out into the possible causes of retinitis pigmentosa, and this may eventually lead to a better understanding of the disease - and perhaps a cure - at some stage in the future.

For more information contact the organisation: Fighting Blindness at 01-8731004 or visit the website www.fightingblindness.ie

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