Choroideremia. What is it? Can Low Vision Help?

Posted on by midwestlowvision

While choroideremia is rare, affecting only 1 in 50,000 to 100,000, I’ve seen several patients with this condition for low vision care over the years and they can be helped. Let’s divide the newsletter into two parts: a current overview of the disease…and typical low vision treatment plans.

retinal photo of a patient with choroideremia
Choroideremia:
an X-linked chorioretinal dystrophy characterized by the progressive degeneration of photoreceptors, choroid, and retinal pigment epithelium; it is caused by mutations in the CHM gene.

Choroideremia (CHM) Overview:
CHM mostly affects males due to its X-linked inheritance pattern, but female carriers can have mild symptoms. Symptoms are similar to retinitis pigmentosa and typically start with night blindness during childhood, leading to peripheral visual field loss and eventually total blindness later in life. Currently, there are no approved treatments for CHM, but several therapeutic strategies are under investigation.

Gene replacement therapy using adeno-associated virus (AAV) vectors is one of the most advanced, and promising, treatment strategies. Other emerging therapies include stem cell treatment, small molecules, retinal prosthesis, and optogenetics, which aim to replace damaged retinal cells, target specific molecular pathways, or use light to control cells in living tissue to restore vision.

Although substantial challenges remain, including understanding the exact pathogenesis of CHM and improving gene editing and cell transplantation methods, these therapeutic developments provide hope for future treatment options. For more information, here are a few of the articles I referenced for this brief overview of choroideremia:
Update on Gene Therapy Clinical Trials for Choroideremia and Potential…
Choroideremia: Update On Clinical Features And Emerging Treatments
Progress in the development of novel therapies for choroideremia

Low Vision Care for the Choroideremia Patient:
Vision Aids: Depending on the stage and nature of vision impairment, magnifying aids may be helpful for reading and other near work. However, I have found that most patients with CHM are more in need of filters to enhance contrast/reduce glare and visual field enhancers for mobility.

Enchroma filter glasses
Enchroma Lx series, CPF’s, NoIR’s, and other companies have a variety of excellent filters that often make an incredible difference to a patient’s visual comfort and function.
reverse telescope fitting set
Reverse telescopes, image minifiers, field expanders, and sometimes prisms are all considered if the acuity is adequate and the visual field is in the ideal range. In my experience, to be effective, the visual acuity needs to be 20/40 or better and the ideal visual field is between 5 to 20 degrees.

As for many with low vision, orientation and mobility training can teach individuals to use their remaining vision and other senses to navigate environments confidently and safely, including the use of white canes and public transportation. Rehabilitation services like occupational therapy can further assist in maintaining independence by focusing on daily living skills. Importantly, psychological support through support groups and counseling can help manage the emotional aspects of living with CHM. Finally, the use of technological solutions, including screen reading software and smartphone apps, can additionally aid those with vision impairments such as CHM.

choroideremia patient wearing special glasses
reverse telescope glasses
the view through a reverse telescope
a patient wearing reverse bioptic telescopes
Both patients above have CHM, but their symptoms and goals were quite different. The first patient above had extreme light sensitivity and needed a filter and a goggle-like seal to block as much light as possible. He wanted a small reverse telescope mounted high, while the patient below had very little light sensitivity and he wanted a wider reverse telescope mounted directly ahead. As I’ve said before, advanced low vision care requires a thorough history, including patient goals, as well as plenty of time for trial and error!

Most of our patients are by referral, but all calls are welcome to see if we can help.  Call 1-877-577-2040 and speak with me or our lead low vision technician, Holly.  Thank you.

Dr. Jarrod Long