Retinal dystrophies are a group of rare diseases that damage the retina, the light-sensitive layer in the back of your eye. The retina sends signals to your brain so that you can see. Inherited means the condition runs in families.
Often these diseases damage rods and cones in the retina. Rods help you see in low light. Cones give you color vision.
There are many different types of inherited retinal dystrophy (IRD). The most common include:
Retinitis pigmentosa (RP) is a group of diseases that cause light-sensitive cells in the retina to die. About 1 in 4,000 people have RP.
Night blindness is usually the first sign of RP. Later, you may have blind spots in your side (peripheral) vision that spread to lessen your sight to the side and eventually your central vision as well.
Choroideremia mostly affects people who were born male. Between 1 in 50,000 and 1 in 100,000 people have this condition.
Often the first symptom is night blindness that starts in childhood. Later, you may develop tunnel vision and find it harder to see details. Choroideremia may cause a complete loss of sight by late adulthood.
Achromatopsia affects cone cells in the retina that help you see color. About 1 out of 30,000 people have this condition.
The main symptom is color blindness. Other symptoms include light sensitivity (photophobia), blurred vision, and involuntary eye movements (nystagmus).
Stargardt disease damages the macula, the middle of the retina that helps you see straight ahead when you read or drive. One out of every 8,000 to 10,000 people have this form of IRD.
The symptoms of Stargardt disease usually show up in children or adolescents, but sometimes not until adulthood. It’s rare for this condition to cause complete blindness.
Cone-rod dystrophy is a group of IRDs that damage cones and rods. Vision loss gets worse over time. Between 1 in 30,000 and 1 in 40,000 people have cone-rod dystrophy.
Symptoms usually start when you’re a child. The first ones to appear are usually blurred vision and photophobia. Later you may have blind spots in the center of your vision and lose your color and peripheral vision.
Leber congenital amaurosis (LCA) begins to damage the retina and cause vision loss in the first few months of a baby’s life. Two to three out of every 100,000 newborns have this condition.
With LCA, your cornea -- the clear covering of your eye -- may be thin and cone-shaped instead of curved. You may be extremely farsighted. Photophobia and nystagmus are also common. In some cases, your pupils may not respond to light, or you may have crossed eyes (strabismus).
These diseases slowly get worse over time. Some can eventually cause severe vision loss or blindness. Although treatments aren't available for most IRDs, there are ways to slow the disease and preserve your sight. Researchers are testing new treatments, and possibly even cures, in clinical trials.
Genes hold the instructions our bodies use to make proteins. When a gene changes, or mutates, your body can't make the protein, or the protein doesn't work like it should.
In IRDs, mutations to one or more genes cause cells in the retina to die. More than 260 different genes cause these diseases. The type of IRD you have depends on which gene or genes are affected.
Retinitis pigmentosa happens from a mutation to any of 60 different genes. Some of these genes are autosomal dominant. That means if your parent has the disease, you have a 50-50 chance of also having retinitis pigmentosa.
Other retinitis pigmentosa genes are autosomal recessive. When both parents are carriers they have the gene, but they don't have symptoms. If both of your parents are carriers, you could be a carrier or have symptoms.
Choroideremia is an X-linked genetic condition. The gene that causes it is on the X chromosome. People who are born female have two X chromosomes. They are usually carriers and don't show symptoms. Because males have only one X chromosome, they do have symptoms.
Achromatopsia can affect any of five different genes that help cones respond to light. When one or more of these genes are mutated, the cones don't work, and you can't see colors.
Stargardt disease happens from a mutation in the ABCA4 gene. This gene codes for a protein that normally removes toxins from the light-sensitive cells in your retina. Changes to ABCA4 cause a fatty substance called lipofuscin build up in and damage the macula -- the part of your eye that helps you see straight ahead.
Cone-rod dystrophy is linked to more than 30 different genes that help the rods and cones in your retina work. The cones usually break down first, which is why light sensitivity is often the first symptom.
Leber congenital amaurosis (LCA) happens from changes to any of at least 14 different genes. You need all of these genes working to have healthy vision. Because mutations disrupt the growth of the retina in the womb, vision loss starts soon after birth.
Vision loss is a symptom of all IRDs. Sight problems can be mild at first, but they may get worse over time.
Which symptoms you have depend on your type of IRD. The most common symptoms are:
- Night blindness -- trouble seeing in low light
- Loss of color vision
- Light sensitivity
- Loss of side or middle vision
Getting a Diagnosis
If your regular eye doctor (optometrist) thinks you may have an IRD, they’ll likely refer you to a specialist in eye diseases called an ophthalmologist. This doctor will perform an exam to check your retina and other parts of your eyes. They’ll ask about your symptoms, and whether any of your family members have retinal disease. Then they’ll use tools like these to take a closer look at your retina and other parts of your eye:
Electroretinogram (ERG) measures the electrical activity in your rods and cones. It can show how well these cells respond to light. Less electrical activity may mean your rods and cones aren't working like they should.
Visual field testing checks your middle and side vision for any blind spots.
Optical coherence tomography (OCT) takes very detailed pictures of your retina. A thinning retina can be a sign of damage from retinal dystrophy.
Color testing includes a few different tests of how well you see colors.
Fundus autofluorescence creates a map of the different layers of your retina. Thinning of the layers can be a sign of IRD damage.
Depending on the results of these tests, your doctor might send you for genetic testing. These tests use a sample of your blood or saliva to find genes that cause IRDs. A genetic counselor can explain the results of your genetic tests.
Questions for Your Doctor
IRDs are rare, and they can be complex to manage and treat. It's good to have as much information as you can about your condition. Take a list of questions like these to ask your doctor:
- What kind of vision loss could I have?
- How quickly might I lose sight?
- Can you treat my condition?
- What treatments are available?
- What lifestyle changes can help me protect my vision
- For what symptoms should I call you?
- What low-vision aids might help me?
Right now, no treatment or cure exists for most forms of IRD. But there are ways to slow vision loss and preserve your sight for as long as possible.
In some studies, high doses of vitamin A slowed certain types of retinitis pigmentosa. But high-dose vitamin A isn't safe for people with Stargardt disease and other retinal diseases, because it can cause even more damage. Check with your doctor before you take any supplement to treat IRD.
You can wear glasses for minor vision problems like farsightedness, nearsightedness, or astigmatism. Glasses won't totally restore your sight, but they could help you see better.
Dark-tinted classes are best for light sensitivity. Lipofuscin absorbs blue light, and then forms substances called free radicals that damages rods and cones. If you have Stargardt disease, your doctor might suggest that you wear brown or amber sunglasses to filter out blue light.
The ARGUS II is the very first artificial retina. This implant can restore sight to some people who have lost vision from retinitis pigmentosa.
Researchers are learning more about the causes of these diseases every day. They're studying new treatments like gene therapy and stem cell therapy, which might one day slow or even cure IRDs. Taking part in a clinical trial can give you access to a new treatment before it's available to everyone else.
Voretigene neparvovec-rzyl (Luxturna) is a type of gene therapy that's already FDA-approved. It treats some people with retinal dystrophy caused by an RPE65 gene mutation. Luxturna sends a normal copy of the gene to cells in the retina to restore vision.
Taking Care of Yourself
Low-vision aids are tools that can help you make the most of the vision you still have. You might try:
- Magnifying lenses
- Computer programs that read printed words out loud
- Devices that increase light
- A cane or guide dog
Your eye doctor can do a low-vision assessment and recommend the tools that will help you most.
Wearing sunglasses helps protect your retina from ultraviolet (UV) light damage. It's also a good idea to avoid smoking, which can damage your retina even more.
Getting regular check-ups will help your doctor spot the signs of vision loss early and manage them.
What to Expect
All IRDs cause some type of vision loss, but the type and speed of that loss are different for each disease.
For example, retinitis pigmentosa is a very slow disease that lessens things like night and reading vision, but rarely leads to complete loss of sight. Achromatopsia mainly affects color vision. Choroideremia can lead to total blindness. Stargardt disease damages central vision, but some people lose that sight more quickly than others.
IRD can affect your life in many ways. Your eye doctor and other experts will offer tips and strategies to help you manage your condition.
A low-vision specialist can recommend tools to maintain your independence. And a social worker can connect you with resources in your area to help you adapt to vision loss.