Cone Rod Dystrophy

What is Cone Rod Dystrophy?


Cone rod dystrophy is an umbrella term that covers about 30 inherited diseases that affect the eye’s cones and rods, which are special types of cells that gather light.

Light carries visual information about the outside world. Light enters the eye through the pupil and strikes the light-sensitive tissue lining the inside of the eye. This tissue, known as the retina, converts the information in the light to electrical pulses; the optic nerve sends the pulses to the brain, which transforms the signals into the images we perceive.

Function of Rods and Cones

The retina contains rods and cones, which work in unique ways to help you see. Rods and cones are photoreceptors, which mean they are cells that absorb light. Exposure to light stimulates rods and cones into doing their job of absorbing light. Rods work at very low levels of light – they are the cells you use for night vision, as it takes very little light to activate your rods. Rods do not help you see color; this is why you cannot see color at night.

The human eye has about 100 million rod cells. As their name implies, rod cells are rod-shaped (long and skinny.) Cone cells, by comparison, are cone-shaped.

The human eye has about 3 million cone cells; most of these are in the fovea, which is a small pit at the back of the eye that helps you see the sharpness and detail of images. It takes a significantly greater amount of light to activate a cone cell compared to a rod. Cone cells help you see colors. You have three types of cones: blue, green, and red.

Deterioration of Rods and Cones

Someone with cone rod dystrophy may begin experiencing diminished acuity, problems with colours, and a decrease in peripheral vision before being diagnosed.

Rods allow for peripheral vision to the far left and right of your field of view; cones enable central vision and help you see details and colors in your field of view. Deterioration of cones and rods can cause decreased sharpness in vision, increased sensitivity to light, impaired color vision, blind spots in the center of the visual field, and partial loss of peripheral vision. Over time, deterioration of the rods and cones can cause night blindness, making reading and other close-up work difficult, and decreased peripheral vision severe enough to limit your mobility.

Cone rod dystrophy is an inherited condition, which means it develops as the result of mutations in genes. These mutations cause a gradual loss of rods and cones in the retina, which results in vision loss. Cones typically break down before rods, so sensitivity to light and loss of color are usually the first symptoms. The loss of night vision comes later.

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Prevalence


Parents who already know that a family member has cone rod dystrophy should bring their kids in for examination by an ophthalmologist, according to a report from FamilyConnect.

If you’ve been diagnosed with cone rod dystrophy, you would be right to wonder how many other people may also have this disease. According to the Orphanet Journal of Rare Diseases, the prevalence of cone rod dystrophies is 1 in 40,000.

Signs and Symptoms


A range of symptoms can occur with cone rod dystrophy, but some are more common than others, notes the NIH.

Depiction of possible vision of someone with optic atrophy, with symptoms such as photophobia and decreased peripheral vision.

For example, as many as 80%-99% of patients will have abnormal pigment in their retina, as well as night blindness (nyctalopia) and profound sensitivity to light (photophobia). About 30% to 79% of individuals with CRD will have abnormal color vision.

Approximately 5% to 29% of patients wind up with impaired vision. A person with cone rod dystrophy may begin experiencing diminished acuity, problems with colors and a decrease in peripheral vision before being diagnosed.

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Causes


The group of eye disorders known as cone rod dystrophy has a number of causes, but they are all inherited conditions passed on from parents to children. The National Institute of Health explains that the 30-plus types of CRD are caused by mutations in multiple genes, meaning there are various ways to inherit this disease.

Low Vision Apps


Apps on a smartphone.

Among the low vision products available to disabled individuals are apps that you can download in an instant over the internet. Make sure that your smartphone’s operating system is up-to-date before downloading low vision apps, to ensure that they will work properly on your device. A good overview of low vision apps is available at iAccessibility.

Of course, you can make adjustments to the phone itself, such as changing the contrast or using an assistant that responds to your verbal commands and reads text to you from the screen.

eSight Eyewear is clinically proven to significantly enhance vision for people living with visual impairments, legal blindness, and vision loss. Discover if eSight is right for you!

Support Groups


When dealing with an ocular disease such as cone rod dystrophy, be prepared for good days and bad days. It can do wonders for your morale to spend time with other individuals with the same type of diagnosis, so you can feel connected and become part of a community. You’ll share stories about your experiences with CRD and see that you’re not so alone, with others going through the same issues. Ask your eye care professional for assistance in finding a local support group.

Available Assistive Technology


With so much information to absorb about cone rod dystrophy, you and your loved ones may be feeling somewhat overwhelmed. You should know that while there currently isn’t a treatment available to stop CRD from causing people to go blind, you may be a candidate for alternative assistive options.

eSight in black; possible assistive technology option for those with cone rod dystrophy.

Many eSight users live with cone rod dystrophy.  eSight is an electronic eyewear for those with low vision. It stimulates synaptic activity from the remaining photoreceptor function of its users’ eyes and provides the brain with increased visual information to naturally compensate for gaps in the user’s field of view. 

Technical Specifications

For those who are legally blind, eSight is clinically validated to enhance vision to up to 7 lines on a doctor’s eye chart. It has a leading edge camera, liquid lens, and high definition display powered by smart algorithms. The high-speed, high-resolution 21.5 MP camera captures and then projects real-time footage onto two OLED screens in front of the eyes. 

As well, for those with cone rod dystrophy who experience photophobia, eSight lets users adjust both the brightness and contrast of the screens, which means it is well-suited for people with light sensitivity. 

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