Eye Info

Understanding retinitis pigmentosa

Summary: Helping you, your friends and family understand more about your eye condition. This information is taken from our "Understanding" series of booklets.

• What is retinitis pigmentosa?
• Can it be detected by an eye test?
• Do people with RP develop cataracts?
• Is RP just an eye condition?
• Can RP be treated?
• What next?
• Useful contacts
• About this guide

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What is retinitis pigmentosa?

Retinitis pigmentosa (RP) is the name given to a group of hereditary eye disorders. These disorders affect the retina, which is the light-sensitive tissue lining the back of the eye, in which the first stages of seeing take place. In RP, sight loss is gradual but progressive. It is unusual for people with RP to become totally blind as most retain some useful vision well into old age.

What is the retina?

The retina in your eye serves a similar purpose to a film inside a camera. Light is focused by a lens at the front of the camera onto a light-sensitive film at the back, to form a picture. In a similar way, light entering your eye is focused onto a light-sensitive tissue which lines the inside of the eye at the back. This tissue is the retina.

The retina consists of two main layers, a thin one called the pigment epithelium and a thicker one, made up of many layers of cells, called the neural retina. One particular layer in this neural retina contains many millions of cells called photoreceptors, which are able to respond to light.

A few million cells called cones are concentrated in the central portion of the retina. These allow us to see fine detail and colour. Away from the central portion of the retina are about 120 million cells, which are mostly rod cells. They enable us to see when light is dim and provide peripheral (side) vision outside of the main line of sight. Peripheral vision is the sight you have out of the corner of your eye when looking straight ahead.

When light is focused onto these rods or cones, a small electrical charge is generated (the amount depends on the amount of light) and this charge passes down the optic nerve to the brain. As each of these cells receives a slightly different amount of light and sends a different electrical pulse, the brain is able to assemble a picture.

What causes RP?

It is now known that there are many different inherited problems causing RP. In all RP-related conditions however, the ability of the retina to respond to light is affected. The problem can be in many parts of the retina such as the rod or cone cells, or in the connections between the cells of the retina.

What are the symptoms of RP?

The most common first symptom is difficulty in seeing in poor light, for example outdoors at dusk, or in a dimly lit room. A second symptom is reduction of the visual field, in which sight is lost from the sides, or from above and below. This is often referred to as tunnel vision and means that the rod cells, and some of the outer cone cells, have been affected first.

In some RP-related conditions central vision is lost first. The first signs of this are difficulty in reading print or carrying out detailed work. All RP conditions are progressive, but the speed at which deterioration takes place varies from one person to another.

In many types of RP, glare from bright lights is an increasing problem, although some people do not experience this until the more advanced stages.

How is RP inherited?

There are three ways in which RP can be inherited:

Autosomal dominant inheritance

This is the pattern of inheritance where RP is known to exist in a family, affecting both males and females. The probability of RP being passed from an affected parent to a child is exactly 50 per cent.

Autosomal recessive inheritance

There will usually be no known history of RP in the family but if two carriers who show no obvious symptoms have a child, there is a 25 per cent chance that he or she will have RP.

X-linked inheritance

This is a pattern of inheritance where only males develop the disease, but female members of a family are carriers. Some carriers can develop a mild form of RP.

For example, if a man has X-linked RP, his sons will not develop RP, but all of his daughters will become carriers. These daughters will each have a 50 per cent chance of producing an affected son and a 50 per cent chance of daughters who will be carriers. This inheritance pattern is sometimes difficult to identify in a family where there have been no sons for several generations, as the faulty gene could have passed down a line of female carriers and then suddenly affect a male child.

These inheritance patterns are explained in detail in the British Retinitis Pigmentosa Society (BRPS) booklet, “Genetics and RP”, obtainable from the BRPS (contact details can be found at the end of this page).

When does RP develop?

There is no hard and fast rule, but in most cases the early symptoms of RP develop between the ages of 10 and 30.

Can it be detected by an eye test?

The types of RP which cause loss of central vision become apparent through an inability to read a test card (eye test chart), but peripheral loss, or loss of side vision, is not so obvious and a person may be able to read an optician’s test card for many years.

The condition is best detected through an eye test or examination by an optometrist (optician) or ophthalmologist (eye doctor). By looking through the front of the eye with a piece of equipment called an ophthalmoscope, an optometrist or ophthalmologist can see clearly to the back of the eye. Normally they would see an orange-coloured area called the fundus. When the patient has RP, the orange surface is broken by black or brown clumps of pigment.

Other tests are available which measure the area of visual field which is still useable and the ability to adapt to low light levels. Many more sophisticated tests are available at eye hospitals and these are explained in detail in the BRPS booklet, “The eye clinic and RP”.

Do people with RP develop cataracts?

Many people with RP can go on to develop cataracts. Cataracts are a clouding of the lens at the front of the eye. They usually occur around middle age in people with RP. When they have reached a certain stage, an eye specialist may recommend their removal, particularly if the cataract is interfering with remaining useful vision not affected by RP. The lens is then either replaced with an implant, or specially made spectacles are prescribed.

After the operation, the patient will still have RP, but if the retina has not deteriorated too far, a limited amount of vision will be restored. This is the most common origin of the “miracle cure” stories which appear from time to time in the press.

Is RP just an eye condition?

Yes, but there are other conditions which people with RP can inherit. One example of this is Usher syndrome, where people develop the dual disability of hearing loss and retinitis pigmentosa. For more information on Usher syndrome, contact Sense.

Can RP be treated?

Currently, no treatment is available to cure RP or arrest its progress. It is the result of incorrect instructions being passed to the body’s chemistry by faulty inherited genes.

However, co-ordinated research, in many centres around the world, has been expanding for around 20 years. Many of the genes responsible for the numerous types of RP have been located and their defects identified. Scientists are following many lines of research, among which is the development of a safe system for introducing corrective genetic material to the appropriate cells of an eye. There is some evidence that this will take hold and assist cell regrowth.

There have also been some very positive developments in stem cell and retinal cell transplantation. However, research in these areas is still in the very early stages. It could take a number of years before these new developments might become available as treatments.

Contact the British Retinitis Pigmentosa Society (BRPS) for news on such developments, other research and articles of interest.

What next?

Talk to someone

The RNIB Helpline can:

• put you in touch with an RNIB specialist advice service such as welfare benefits and rights, education, employment, legal rights, emotional support, daily living help and residential care
• send you free information and leaflets
• give you details of support groups and services in your area.

Call us Monday to Friday 9.00 am – 5.00 pm on 0845 766 9999 or 020 7388 2525 (some callers may find it cheaper to call a landline, so we have detailed both 08 prefixed numbers and landline equivalents where available).

Unfortunately, RNIB can only answer email enquiries from the UK. But you may find an organisation for people with poor sight in your country through our agencies database.

Get information

RNIB's guide to Adapting to sightloss offers ideas for people with sight problems on making life easier and ways of getting the most out of life.

You may also find the following useful:

• Find a Low Vision or Hospital Information service near you
• Education
• Employment
• Friends and Family.

Useful contacts

British Retinitis Pigmentosa Society
PO Box 350
Buckingham
MK18 1GZ
Helpline: 0845 123 2354

Royal College of Ophthalmologists
The Royal College of Ophthalmologists is unable to comment on individual patient care.

Sense – UK Deafblind Charity
11-13 Clifton Terrace
Finsbury Park
London
N4 3SR
Telephone 0845 127 0060
Information Service telephone 020 7561 3384
Text 020 7272 9648

About this guide

This information has been produced jointly by the Royal College of Ophthalmologists and Royal National Institute of Blind People, with sponsorship from Alcon Laboratories (UK) Ltd.

© RNIB and RCOphth 2007

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Content author: eyehealth@rnib.org.uk

Last updated: 20/11/2008 11:13