Retinitis Pigmentosa is not a single condition; rather, it's used as an umbrella term for a group of inherited eye conditions that could result in sight loss. It affects the retina, a part of the eye responsible for the transmission of light, and it's usually caused by a malfunction in the rod cells, which control night vision, or in the cone cells, responsible for seeing light and colours.
In this article we'll explore how it can affect your vision and what causes it.
What causes it?
Retinitis Pigmentosa is a hereditary condition. We inherit genes from our parents that contain information on how our cells should work. When there's a fault in these genes, the cells don't know how to work properly. In this case, the cells responsible for growing and maintaining the retina stop working and the body is unable to replace them.
There are three main ways in which it can be inherited:
- Autosomal recessive: Both parents carry the faulty gene, resulting in two copies of the gene being inherited by the child. In this case, the child could develop retinitis pigmentosa, become a carrier or simply be unaffected.
- Autosomal dominant: One of the parents has a dominant faulty gene and usually will have developed the condition. In this case there is a 50% chance that the child will also develop the condition.
- X-linked: This type is related to our sex chromosomes, which contain our DNA. Men have one X chromosome and one Y chromosome, while women have two X chromosomes. The gene that affects retinitis pigmentosa is found in X chromosomes, which means:
- Men with a faulty gene will have the condition and will pass the gene to his daughters, who will become carriers, but not to his sons.
- Women with a faulty gene in one of her X chromosomes but a normal gene on the other will be carriers but will either have a more mild version of the condition or won't develop it at all.
Parents might carry the faulty genes but not develop retinitis pigmentosa, which explains why many people with this condition don't know any family members who have it. In these cases, genetic testing might be needed to find out how it was inherited.
Symptoms might appear very early, and they commonly do so between childhood and the age of 30. They include:
- Difficulty seeing in low light conditions. It's usually the first symptom you'll notice, and it means that it might become harder to see at night or in dark or dimly lit rooms. For most people with healthy vision it takes between 15 to 30 minutes to fully adapt to low light conditions, but for people with retinitis pigmentosa this might take much longer or not happen at all.
- Loss of peripheral vision: As the condition evolves, you'll experience a gradual loss of side vision that can develop into "tunnel vision", finding it difficult to see things to the sides or above and below when looking straight ahead.
- Loss of central vision: More rarely, patients could lose their central vision instead of their side vision, making it difficult to read and perform close tasks.
- Photophobia: People with retinitis pigmentosa are often prone to a higher sensitivity to bright light conditions.
(Loss of peripheral vision or "tunnel vision")
Retinitis pigmentosa can eventually lead to blindness, but most patients will retain a small amount of vision. Also, sight loss happens at different rates. For some it happens quite slowly, with only a small loss of sight over years. Others experience periods of rapid loss with years in between with no apparent decline. Because it is a hereditary condition, the pattern could be similar within members of the same family.
Prevention and Treatment
Since it's a genetic condition, retinitis pigmentosa can't be prevented. Because of this it's important to have regular eye checks and tell your optician or eye specialist if there's a history of this condition in your family.
Genetic counselling might also be helpful and is usually recommended if you have undergone genetic testing. It can help you understand the condition and how it is transmitted better, especially if you have or are thinking about having children.
Unfortunately, there is not current treatment for retinitis pigmentosa, although there is ongoing research on the condition. Your doctor will be able to discuss some options to help you with the symptoms, and there are also different tools to help you make the most out of your remaining vision and make your life easier, such as magnifiers and high quality illumination.
If you develop photophobia, a good pair of tinted sunglasses or eye-shields will help you protect your eyes from the light. Just make sure they have the correct levels of light transmission and give you 100% UV protection.