Retinitis Pigmentosa |
What is Retinitis Pigmentosa?
Retinitis Pigmentosa is a term that refers to a group of hereditary disorders that affect the retina's ability to respond to light. It primarily affects rod cells, the photoreceptor cell that is responsible for night vision, seeing in dim light, and peripheral vision. The loss of peripheral vision is referred to as Tunnel Vision.
The EyeThe eye is a hollow sphere, with a lens at the front which focuses light onto a light sensitive tissue, which lines the inside of the eye at the back.
 The Retina is the light sensitive tissue inside the eye in which the first stages of seeing take place.
This tissue is called the Retina and it is the area affected by all types of RP. In RP disorders, various parts of the Retina cease to function.
The Retina consists of two main layers, a thin one called the pigment epithelium and a thicker one called the neural retina.
The cells in the neural retina are arranged in layers and one of these is made up of photoreceptor (light responding) cells.
There are two types of photoreceptor cells, one called rods and the other called cones. The cone cells are concentrated near the centre of the Retina and are responsible for seeing colour and detail in good light conditions.
The rod cells are found towards the edges of the Retina and are used in poor light or to see items to the side of our line of vision. For example, you will be using your cone cells to read this but your rod cells will give warning of a stool in the middle of the floor or an overtaking car when you are driving. The rod cells will also be used when walking down an unlit road at dusk.
We have far more rod cells than cones. The Retina of a human eye will contain about 120 million rod cells but only 6 million cone cells.
Who it affectsIt is relatively rare and it is estimated that over 25,000 families in the UK are affected. It is also estimated that 1 in 80 of the population carries the gene responsible for RP. 1 in 20 people who are born deaf can develop RP in their late teens (Ushers Syndrome).
All RP conditions are progressive but the rate varies greatly. Some people have lost all their sight in their forties, others have retained useful sight into old age. People registered blind with RP may retain enough central vision to read but have great difficulty in unfamiliar surroundings.
It is not uncommon for people with RP to develop other complications such as cataracts and sometimes swelling at the back of the eye. The cataract can be removed and the lens can be replaced, but this will not affect the underlying RP.
Signs and Symptoms Symptoms of RP usually manifest between the ages of 10 and 30.
Any loss of vision is usually peripheral and cannot normally be picked up by a simple eye test.
At first, there is a decrease in night vision and the inability to see in dimly lit places such as cinemas and theatres. The progressive loss of peripheral sight leads to what is called tunnel vision.
For some types of RP glare from bright lights becomes a problem at more advanced stages of the disease.
The gradual reduction in the ability to see peripherally may cause tripping over objects or a motor vehicle accident. The rate of progression of the disease varies among patients and the type.
Most patients are legally blind around the age of 40.
InheritanceThere are a number of ways in which RP is passed on. It may be caused by mutations in any one of at least ten different genes
If it is known to exist in one parent, the chance of inheritance is 50%.
Women can be passive carriers of the gene with only their sons being affected and they themselves are not normally troubled visually.
Some people develop the condition without any previous family history when the disease is described as being recessive.
TreatmentNo treatment has yet been developed though there is considerable genetic research underway. |
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 Sight loss
Sight Loss and Registration
Sight loss
Cataracts
Diabetic Retinopathy
Glaucoma
Macular Degeneration
Retinitis Pigmentosa
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