Choroideremia: Understanding the Progressive Inherited Retinal Disease

Medically reviewed by Tina Patel, Contact Lens Optician at Feel Good Contacts

Choroideremia is an inherited retinal disease that occurs due to a fault in the CHM gene, this genetic disorder causes tissue damage in the eye and can result in progressive vision loss or blindness.

Causes of choroideremia

Choroideremia causes are due to a fault in the CHM gene, this gene is partly responsible for the healthy functioning of the cells within the retina. When there is a fault with this gene, it causes oxidative stress to the retina which can then cause damage and vision loss as a result.

As women have both an X and a Y chromosome, if they develop choroideremia they don’t usually get severely affected, some don’t get any symptoms at all. Men have two X chromosomes, because choroideremia is an X chromosome condition, this means that men are most affected by it because women have the Y chromosome to compensate, whereas men don’t.

Symptoms and progression of choroideremia

Choroideremia mainly affects young males (as early as 5 years old). The condition gets progressively worse as time goes on, but the rate of progression is not always the same and can vary from person to person. Choroideremia symptoms include:

• Night blindness – difficulty with seeing things in the dark
• Lack of colour perception
• Issues with depth of field
• Blurry vision
• Loss of peripheral vision (tunnel vision)
• Severe sight loss/blindness

Diagnosis and genetic testing

An ophthalmologist will diagnose your condition, but you may need to be referred by your optician or GP. The eye care specialist will test your visual field and assess the retina for any signs of damage.

Treatment options and management

Unfortunately, there are no choroideremia treatment options yet available for this condition. In terms of choroideremia research, gene therapy trials have begun which aim to slow down the progression of the disease or in the best-case scenario, stop the progression of the condition altogether.

This type of gene therapy involves introducing new copies of the affected gene into the eye, to encourage healthy functioning of the retina. The fluid of the eye is drained, then the genes are injected via some fluid underneath the retina. This fluid is then absorbed into the eye and the fluid that has been drained will naturally replenish itself over the course of a few weeks.

Clinical trials for gene therapy started in 2014, with a follow up trial occurring in 2016, both showed promising results for the future of this treatment.

Support and resources

If you or someone you know is living with vision loss or low vision, the NHS and The Royal National Institute of Blind People (RNIB) have some excellent resources for helpful tips to make life a little easier. These tips include:

• Using a magnifying glass
• Making digital screens larger and increasing the size of the font
• Using screen readers and reading aids
• Attending a low vision centre for additional support

You can also register as visually impaired or a person with low vision which can then make you eligible for certain discounts and benefits designed to make everyday life more manageable.

Conclusion

Choroideremia is a hereditary condition that does not yet have an effective treatment option. Those who are living with the condition and have low vision as a result can access tips online and in person via local clinics to discover the best ways of managing day-to-day tasks whilst living with impaired vision.