array(0) { }

Choroideremia

Jump to: Cause & Inheritance | Symptoms | Diagnosis | Treatment & Care | Research & Clinical Trials | Resources | References

overview

Choroideremia is a rare genetic disease that causes progressive vision loss and blindness, mostly in males. 

Choroideremia affects about 1 in every 50,000 to 100,000 people and is a type of inherited retinal disease (IRD). [1] 

Cause & inheritance

Choroideremia is caused by a change (mutation) in a gene called choroideremia or CHM, which is found on the X chromosome. Males have one X and one Y chromosome (XY), so if their only copy of the CHM gene is mutated, they will have choroideremia. Females have two X chromosomes, so if one copy of the CHM gene is mutated, the other copy usually compensates for it. Because of this, choroideremia almost always affects males and is called an X-linked disease. In rare cases, females with two damaged CHM genes may also have symptoms. 

The CHM gene makes a protein called REP-1. REP-1 helps other proteins move to the right places in retinal cells so they can perform their jobs. The retina is a thin layer of tissue at the back of the eye that senses light and sends visual signals to the brain. Without REP-1, cells in the retina don’t work properly and begin to die. Cells that are affected are: 

• Photoreceptors, the light-sensing cells in the retina 
• The choroid, a layer of blood vessels that brings oxygen and nutrients to retina cells  
• Retinal pigment epithelia (RPE) cells, that provides essential functions to keep photoreceptor cells alive 

Symptoms

The first sign of choroideremia is usually night blindness (called nyctalopia), which means it’s hard to see in the dark and low light. This usually starts in childhood, around grade school. 

Other symptoms include:  

• Progressive loss of peripheral vision   
• Tunnel vision  
• Loss of visual acuity (sharpness)  
• Loss of ability to see colors well   
• Increasing vision loss from the side that can progress to blindness 

Most males with choroideremia lose their sight slowly over time. Many become legally blind around age 40, and some lose all their vision by age 70 or 80. However, how fast and how much vision is lost can be different for each person—even in the same family. 

About 30% of females who carry the faulty gene also have some vision loss, but it’s usually milder. 

Diagnosis

Choroideremia often looks similar to other eye diseases, including retinitis pigmentosa. Because of this a family history is helpful and the best way to confirm the diagnosis is through genetic testing—a blood test that checks for changes in the CHM gene. 

Some eye tests can also help. These include: 

• ERG (electroretinography): Measures how the retina responds to light using special contact lenses and flashing lights. 
• OCT (optical coherence tomography): Takes detailed pictures of the retina to show any tears or splits. 
• Visual field test: Shows which parts of your vision are missing by testing where you can and can’t see flashes of light. 

Treatment & CARE

There is currently no cure or treatment for choroideremia. However, scientists are testing gene and optogenetic therapies for choroideremia in clinical trials. 

While we wait for new treatments, making some healthy lifestyle choices might help slow down vision loss [2]. Experts recommend: 

• Wearing UV-blocking sunglasses when outside 
• Eating plenty of fresh fruits and leafy green vegetables 
• Taking antioxidant vitamins 
• Getting enough omega-3 fatty acids, which are found in foods like fish, flaxseeds, and walnuts 

One study also found that a supplement called lutein can increase healthy pigments in the eye. Over time, these pigments may help slow down damage to the retina [3]. 

Research & clinical trials

Many research groups are working to develop new treatments for choroideremia specifically and inherited retinal diseases more broadly. This includes treatments that protect the retina from further damage, correct the underlying genetic mutation and even restore vision when it has already been lost.  

Some of the most promising areas of research include:  

• Gene Therapy: These trials test ways to replace the faulty CHM gene with a healthy one, so the eye can make the REP-1 protein again. Fighting Blindness Canada supported Dr. Ian MacDonald to test a CHM gene therapy in a clinical trial.  
• Stem cell therapy: Clinical trials are studying retinal cells made from stem cells to see if they can restore vision in people with retinal degenerative diseases like choroideremia. 
• Optogenetic therapy: This therapy helps people who have lost most of their photoreceptor cells. Special genes called opsins are injected into the eye to turn non-light-sensitive cells into light-detecting ones.  
• Visual Protheses: A bionic eye, also called a visual prosthesis, is an electrical implant that is surgically inserted into the eye. It improves light sensitivity and creates a sense of vision for people who have advanced vision loss. Most of the devices being developed are for individuals who have retinal degeneration.  

Discover more information on clinical trials for choroideremia. 

resources

Fighting Blindness Canada has developed resources to help you navigate vision care. Follow the links below to learn more.  

• Sign up for our e-newsletter to keep up to date on the latest breakthroughs and community events.  
• Contact our Heath Information line by email or phone to ask questions about your eye health.  
• Hear about the latest in vision research and connect with others at our View Point educational series.
• Learn about genetic testing and join our Inherited Retinal Disease Patient Registry to connect with clinical trials and treatments.  
• Discover more information on clinical trials for Choroideremia. 
• Learn more about all of Fighting Blindness Canada’s funded research. 

REFERENCES

[1] https://ghr.nlm.nih.gov/condition/choroideremia#statistics 

[2] https://www.ncbi.nlm.nih.gov/books/NBK1337/ 

[3] https://www.sciencedirect.com/science/article/abs/pii/S0014483501911261?via%3Dihub  

---

Updated on April 9, 2025