Who would have thought there could be a group of eye diseases under one umbrella with almost the same symptoms? But here we have it… Cone rod dystrophies. Cone rod dystrophy is a group of related eye diseases that cause vision loss, which gets worse with each passing minute. The severity of cone rod dystrophies is time-dependent, the longer you leave it undiagnosed and untreated, the more severe it gets.
The retinal disorders of cone rod dystrophy affect the retina, a light-sensitive tissue layer at the back of the eye. Vision loss is a result of light-sensing cells of the retina beginning to gradually deteriorate.
Let’s have a little recap of the signs and symptoms of cone rod dystrophy.
Signs and Symptoms of Cone Rod Dystrophy
Often occurring during childhood, the first sign and symptom of cone rod dystrophy is reduced sharpness of vision (visual acuity) and increased sensitivity to light (photophobia). At a later stage, most likely into adulthood, impaired color vision, blind spots in the central vision, and partial side (peripheral) vision loss are among the symptoms of cone rod dystrophy as well. Over time, an affected person may develop night blindness and worsening of peripheral vision loss, limiting mobility. Reading becomes difficult with reduced visual acuity, and most individuals are declared legally blind by mid-adulthood.
Not exactly your walk-in-the-park kind of eye disease. Cone rod dystrophy is a group of 35 inherited diseases, which means all cone dystrophy and cone rod dystrophy are genetic conditions. You can take the necessary precautions if any variation of cone rod dystrophy is present in your parents.
Here’s a small dive into the different types of cone rod dystrophies based on their genetic cause and the way they are inherited.
Type of Inheritance Patterns of Cone Rod Dystrophy
Multiple mutated genes can cause cone rod dystrophies, which leads to loss of cone and rod photoreceptor cells. Among the 35 genes linked to this condition, it includes ABCA4, CRX, GUCY2D, and RPGR.
The varied inheritance patterns of cone rod dystrophy include autosomal dominant, autosomal recessive, and X-linked.
Out of these three, autosomal recessive is the most common pattern of inheritance. It means that both copies of mutated genes give rise to this condition. Hence, both the mother and father have passed on the mutation of the gene in question.
In autosomal dominant inheritance pattern, one copy of the gene is mutated, and the person receives one copy of the mutated gene from an affected parent.
The X-linked inheritance pattern is a little straightforward and can only be passed on through the father. This is because a male only has one functioning X-chromosome. Hence, if a mutated gene is present in the X-chromosome, the condition is passed on. As women almost always have another functioning X-chromosome, they typically don’t develop the condition.
Even with the defined inheritance patterns of cone rod dystrophy, some form of it may occur spontaneously without any apparent reason. This happens when a new genetic mutation may have occurred, causing the condition to develop.
How is Cone Rod Dystrophy Diagnosed?
Your eye doctor can diagnose for cone dystrophy and cone rod dystrophy based on the presenting symptoms, clinical examination and by performing an electro-diagnostic test of the retina, known as the electroretinogram (ERG).
The ERG helps assess the overall function of the photoreceptor cells in the retina. Upon assessment, it will be apparent that the cone function is severely reduced in cone and cone rod dystrophies. Yet, in cone dystrophy, the rod function would be preserved and would be less severely affected in cone rod dystrophy.
To further progress with the diagnosis, your ophthalmologist may use a special camera to take pictures of the retina to assess the health and integrity of the various retinal cells.
For a complete and definitive diagnosis, genetic testing would help identify mutations in any of the 30 genes associated with cone dystrophy and cone rod dystrophy.
General Medical Assessment
As cone rod dystrophy is a genetic condition, it may also affect other parts of the body, which may be a direct result from conditions like Bardet-Biedl and Alström syndrome. Hence, some children, with probable cone rod dystrophy, are referred to a pediatrician and other specialists for further assessment, including but not limited to:
- General physical examination
- Blood tests
- MRI (magnetic resonance imaging)
- Hearing assessment
- Heart tracing (electrocardiogram) and echocardiogram
- Ultrasound of the kidney and liver (if indicated)
We have got the basics down for you, and we’re sure you have got the hang of various aspects of cone rod dystrophy. Let’s take a look at how common the disease is.
Prevalence of Cone Rod Dystrophy
Surprise surprise… Cone rod dystrophies only occur in 1 out of 30,000-40,000 people. Hence, it’s a relatively rare genetic disease, yet it affects a vast amount of people in North America and around the world.
So if you’re someone with cone rod dystrophy and have kids or know any children in your family whose parents are affected by cone rod dystrophy, you should get them in for an examination by an ophthalmologist.
Furthermore, based on the genes involved in cone rod dystrophy, ABCA4 is responsible for 30 to 60% of the autosomal recessive cone rod dystrophies. CRX and GUCY2d are responsible for many reported cases of autosomal dominant inheritance pattern and RPGR is responsible for X-linked patterns.
Is There a Way to Overcome Cone Rod Dystrophy?
Is there a cone rod dystrophy cure? Are there any treatment options available for cone rod dystrophies? What about therapies? These questions are likely rolling around in your mind by now. Knowing the severity and the progression of cone rod dystrophy, you’re likely reeling and would want to get the answers as soon as possible.
However, sadly, there is no cure or treatment (yet) for cone dystrophy and cone rod dystrophy. But there are ways to manage the symptoms and slow the progress of the condition and live a fairly independent life.
You can maximize on the available vision and get access to social support. Here are a few ideas to get the ball rolling:
- Attend a low vision clinic that provides access to low vision specialists, visual aids, and visual rehabilitation services
- Use assistive technologies to improve the quality of life
- Use tinted glasses or contact lens in bright lights to reduce light sensitivity and improve visual sharpness
- Preferential seating in classroom
- Register your child as sight impaired (SI) or severely sight impaired (SSI) for access to social support and financial concessions (if eligible)
- Get in touch with national or local charities for advice and peer support
Visual Aids for Cone Rod Dystrophy
Visual aids, especially assistive technology, are highly beneficial for someone affected by cone rod dystrophy. Why? Assistive technology visual aids provide a person with an independence that we all crave and take pride in. These visual aids, optical and non-optical, are usually designed to help people with vision loss or other disabilities, including everything from screen readers or screen magnifiers for low-vision computer users, video magnifiers and other devices for reading and writing with low vision, to braille watches and braille printers.
Among these, we have visual aids designed for people who have vision loss or declared legally blind, due to various eye diseases and conditions. IrisVision is an effective low vision, assistive technology visual aid that assists in enhancing the remaining vision of an affected person.
You can check out the story of Ed, who suffered from Retinitis Pigmentosa, a form of cone rod dystrophy and how IrisVision was able to turn his life around.