What is retinitis pigmentosa or RP?
Retinitis pigmentosa, also known as RP, develops as a result of certain genetic disorders which cause the breakdown of cells in the retina.
The retina sits at the back of the eye and is responsible for converting light into signals to the brain, thereby giving us the ability to see.
Once these photoreceptor cells in the retina begin to degenerate, the person with RP will notice a gradual decline in their vision usually struggling to see at night and losing their peripheral vision.
Causes of Retinitis Pigmentosa (RP)
The majority of people with retinitis pigmentosa will have inherited it from their parents. There are several genetic conditions that cause retinitis pigmentosa. These genetic malfunctions affect the genes responsible for making proteins that are needed in the photoreceptor cells in the retina. In the absence of this protein or any damage to it, the photoreceptor cells stop working and begin to die.
Symptoms of Retinitis Pigmentosa (RP)?
The first symptoms of retinitis pigmentosa are usually picked up between the ages of 10 and 40, but they can be identified in younger children when both eyes are affected.
With such a range in the age of onset for retinitis pigmentosa, it can be difficult to predict the extent and timescale of deterioration in your vision.
RP symptoms usually begin with poor night vision as the cells, or rods, that are in charge of seeing in dim light begin to stop working. In most cases, it takes our eyes about 20 minutes to adapt to low-light conditions but with RP it can take much longer or not happen at all. Eventually you may be diagnosed with ‘night blindness’ which will likely restrict your ability to drive to the daytime only.
As retinitis pigmentosa progresses, the cones (cells which respond to light) will stop working too. Cones are used for peripheral vision - what you can see on the edges of your eyesight. Losing the cones will result in what is known as ‘tunnel vision’ as you struggle to see anything to the sides and above or below when you look straight ahead.
Although less common, people with retinitis pigmentosa may also lose some of their central vision making it hard to focus on small jobs such as reading.
How is retinitis pigmentosa inherited?
There are three main ways in which retinitis pigmentosa can be passed from parent(s) to child. In some cases, a person can be a carrier of the disease but not develop it:
Autosomal recessive inheritance
Caused as a result of two copies of the mutated gene being present since both parents are carriers. It may be that the child is a carrier or develops the disorder. However, it can also not affect the child at all.
Autosomal dominant inheritance
Caused as a result of one parent having a dominant gene mutation. There is a 1 in 2 chance that the child will inherit and then develop retinitis pigmentosa.
If the mother is the parent with RP linked to their X chromosome, there is a 1 in 2 chance of their son developing RP and the same odds of their daughter being carrier.
How is retinitis pigmentosa diagnosed?
One of the key points to remember with an RP diagnosis is to ensure that your optometrist knows if there is a history of it in your family. This will allow the optometrist to take a closer look at your retina during an eye test.
In some cases, the optometrist can detect specific signs at the back of the eye, within the retina, which indicate RP. A field test can also assess the function of the peripheral retina, to check for defects in vision.
If your optometrist detects any signs of retinitis pigmentosa, they will refer you to an ophthalmologist – an eye doctor - who will perform further tests including assessing the electrical signals sent by the eye to the brain and a genetic test for the retinitis pigmentosa faulty gene.
Once diagnosed, a person with RP can be closely monitored and be made aware of any new treatments.
Can retinitis pigmentosa be prevented?
Because it is a genetic condition that is inherited from one or both of your parents, retinitis pigmentosa cannot be prevented. It is therefore really important that you have regular eye tests and, if someone in the family develops problems with their retinas, make sure you tell your optician.
You can also help your eyes by making sure they are fully protected in sunlight.
Retinitis Pigmentosa Treatments
While research continues, there is no cure for retinitis pigmentosa. Intensive research is being done all over the world to identify the causes, means of prevention and possible treatments.
One school of thought thinks that high doses of vitamin A can slow down retinal degeneration, but there's very little evidence to support this.
Your ophthalmologist will be able to talk you through anything that might help ease symptoms.
Living with RP
Once diagnosed with retinitis pigmentosa, there will be a team of professionals and organisations to help you manage any vision loss and the impact it might have on your life.
This may include special lighting, training on how to stay mobile with limited vision and perhaps the use of a cane or guide dog so that you can maintain your independence.