Cone-Rod Dystrophy

What is cone-rod dystrophy?

Cone-rod dystrophy (CRD) is a type of retinal disease that causes gradual vision loss. Eventually, it causes total vision loss (blindness). The vision loss happens as the condition affects photoreceptors (cones and rods) in your retina. CRD is rare and usually genetic. It typically starts early in life, either during childhood or early adulthood.

Dystrophy of the cones and rods means they start to break down. As cones break down, your color vision and central vision acuity (clarity and sharpness) decrease. When rods break down, it affects night vision and peripheral vision. Cones usually begin breaking down first (though sometimes, cones and rods break down at about the same time).

What are the symptoms?

Possible CRD symptoms include (generally organized from early to late stage):

• Weakening vision in the center of your visual field (this usually starts during childhood).
• Pronounced sensitivity to light (photophobia).
• Trouble distinguishing colors and, eventually, color blindness.
• Night blindness (nyctalopia).
• Peripheral vision loss
• Total vision loss (blindness — the most advanced stage).

What causes cone-rod dystrophy?

CRD is usually genetic, meaning it happens because of DNA changes. So far, research shows at least 28 separate mutations can cause it. Those mutations can be:

• Autosomal dominant (you can inherit it if only one biological parent passes the mutation to you).
• Autosomal recessive (you can only inherit it if both biological parents pass the mutation to you).
• X-linked (variable risk depending on which biological parent has the mutation).

The four gene mutations that are most likely to cause cone-rod dystrophy include:

• ABCA4.
• CRX.
• GUCY2D.
• RPGR.

How is cone-rod dystrophy diagnosed?

An eye care specialist can diagnose cone-rod dystrophy using a combination of methods and tools. That includes getting a detailed history, including asking about your medical history and any vision loss or changes you’ve experienced. They’ll also perform an eye exam, which can include any of the following:

• Visual acuity test.
• Color vision test.
• Slit lamp exam.

While those methods are helpful, the main test to diagnose cone-rod dystrophy is a special ophthalmic electrophysiology test called electroretinography. This test measures retinal activity directly and can detect specific activity patterns (or lack thereof) that can confirm or rule out CRD.

Your eye care specialist or a healthcare provider may also recommend genetic testing to see if you have a mutation known to cause cone-rod dystrophy. Your provider will likely recommend this testing if a close family member (a biological parent, sibling or child) develops CRD or if there’s a chance you might pass CRD to your biological children.

How is cone-rod dystrophy treated?

Unfortunately, there isn’t a treatment for CRD. For now, the only approach is to slow its progression (how fast it gets worse). Your eye care specialist can treat some of the symptoms or complications. That often includes:

• Light protection. Using light-blocking accessories (like sunglasses or tinted eyeglasses or contact lenses) can slow the breakdown of retinal cells from light exposure.
• Vision correction. Prescription lenses can help compensate for decreasing vision early on.
• Low vision aids. Tools, devices and technology — from low-tech items like magnifying glasses to high-tech items like screen-reading computer programs — can help you work around the vision loss.
• Visual rehabilitation. This form of rehab therapy helps you learn ways to compensate for or work around vision loss.
• Nutritional supplements. Some micronutrients (vitamins or minerals) may help slow CRD progression. Your eye care specialist can tell you more about this and guide you on which supplements to use or not use.
• Mental health support. Losing your vision can be a stressful and scary experience. Many people with CRD experience anxiety or depression symptoms related to the changes from their vision loss. Mental healthcare and support can help you process your emotions and develop ways to cope with them.

Research and future treatment options

Researchers are currently investigating if gene therapies can treat cone-rod dystrophy. But those treatments are still in the very early testing phases of the research process. That means it will be several years (at minimum) for those treatments to become available. That also hinges on if the research shows they’re safe and effective. While that means those treatments aren’t an option right now, they may offer hope in the future to those with CRD.

Can this cone-rod dystrophy be prevented?

Cone-rod dystrophy is a disease that usually happens because of genetic mutations. So there’s no way — at least for now — to prevent CRD or reduce your risk of developing it. Researchers are still looking for other causes or contributing factors.

What can I expect if I have cone-rod dystrophy?

The effects of cone-rod dystrophy start during childhood. Children with CRD usually have vision issues before age 10, so teachers or other education professionals may be the first to notice the effects.

Many people with cone-rod dystrophy often have vision loss severe enough to meet the criteria for legal blindness by age 20. But sometimes, the damage is slower and/or less severe, delaying vision loss. People with slower-progressing CRD may not meet the legal blindness criteria until their 30s or 40s.

What’s the outlook for cone-rod dystrophy?

CRD isn’t life-threatening, but it is a disruptive — and eventually disabling — condition. You can learn to live with vision loss, especially with assistance from medical professionals, support programs and other resources.

How do I take care of myself if I have cone-rod dystrophy?

If you have CRD, it’s important to see an eye care specialist regularly so they can monitor your eyes for changes and help adjust treatments accordingly. They can also keep you informed about treatment option changes or other things you need to know.

Your eye care specialist and other healthcare providers can greatly help you during the progression of cone-rod dystrophy. They can help you learn how to work around it and prepare you to deal with what’s to come. Part of their job also involves staying up to date with research advances so they can help you stay informed about new treatments that might help.

What questions should I ask my doctor?

Some important questions you may want to ask include:

• How advanced is my vision loss?
• How will the CRD progress and what is the most likely timeline?
• Should I and/or other family members undergo genetic testing to determine the DNA mutation(s) behind the CRD?
• What can I do now to delay the progression?
• Are there programs or resources that can help me adapt to current changes or prepare for future ones?