Cone-Rod Dystrophy
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What Is Cone-Rod Dystrophy?
Cone-rod dystrophy is a group of more than 30 inherited diseases that, over time, cause deterioration of the specialized light-sensitive cells of the retina—the rods that densely cover the peripheral, or outlying, portion of the retina and are responsible for peripheral vision and vision in low light, and the cones which more densely cover the central portion of the retina and are responsible for color perception, detailed vision, and central vision.
People with cone-rod dystrophy typically experience decreased sharpness of vision followed by a loss of peripheral vision and color perception. The most common form of cone-rod dystrophy is retinitis pigmentosa. There is no treatment or cure for this disease, which is also referred to as cone-rod degeneration, progressive cone-rod dystrophy, and retinal cone dystrophy.
Cone-rod dystrophy can be stable (usually present at birth and does not worsen over time) or progressive (age of onset varies greatly and will worsen over time).
How Is Cone-Rod Dystrophy Diagnosed?
The first symptom of cone-rod dystrophy is decreased detailed vision which is not correctable with glasses. You may also notice light and glare hurting your child’s eyes and limiting his or her vision.
A dilated eye examination will reveal degeneration of the rods and cones, and the child will be given a diagnosis of cone-rod dystrophy. Additionally, if a family member has a diagnosis of cone-rod dystrophy, your child’s peripheral vision and eyes should be examined by an ophthalmologist. Genetic testing is also available to help determine an early diagnosis. An early diagnosis enables a person with the disease to prepare for its progression.
Are There Treatments for Cone-Rod Dystrophy?
There is currently no cure or standard, proven treatment for cone-rod dystrophy. Some ophthalmologists believe that treatment with high doses of Vitamin A can slow the progression.
It is important to protect the eyes from further damage from the sun by using quality sunglasses and a hat while outdoors in the daytime.
How Would You Describe the Eyesight of One with Cone-Rod Dystrophy and How Will My Child Function with It?
Cone-rod dystrophy typically manifests with loss of sharp visual acuity, which is not correctable with glasses, severe sensitivity to light (photophobia), central blind spots in the vision (scotomas), and progresses to poor vision in dimly lit environments (“night blindness”) and peripheral field loss, which may be progressive.
Your child’s teacher of students with visual impairments should perform a functional vision assessment to determine how your child uses his or her vision in everyday life and a learning media assessment to determine which senses your child primarily uses to get information from the environment. These assessments, along with an orientation and mobility assessment conducted by a mobility specialist, will give the team information needed to make specific recommendations for your child to best access learning material and his or her environment.
Loss of sharp visual acuity makes it difficult to recognize faces and facial expressions, access information from a classroom board or wall, view a speaker or performance, read print, and perform visual tasks of fine detail such as threading a needle. In order to best use remaining vision, your child can be taught to increase the contrast of the environment, increase the contrast of print by using a CCTV or screen-magnification software, and increase task lighting. Furthermore, your teen should sit in a preferred seat of a room for optimal viewing, whether near or far from the lecture or activity.
Bright sunlight and glare can cause significant discomfort and inability to see (this is known as a “whiteout”). Your child may benefit from specialized sunglasses (amber-tinted lenses), use of a brimmed hat while outdoors as well as shutting blinds while indoors if glare is present.
A child with loss of peripheral vision has some degree of “tunnel vision” making it difficult to gather comprehensive visual information in an environment; he or she will benefit from learning visual efficiency skills such as scanning an environment in an organized manner and possibly using a reverse telescope to minimize the appearance of an image and see its entirety within the remaining field of vision. Additionally, the person is likely to bump into side-lying and low-lying obstacles; he or she should utilize orientation and mobility skills, such as the use of a cane, to avoid obstacles.
Orientation and mobility (travel training) becomes necessary to navigate safely with the use of a cane and public transportation. Evening travel may be further aided by the use of an infrared night scope.
If your child loses central vision in addition to lost peripheral vision, he or she must be taught to complete tasks without the use of vision. Your child may be taught braille, screen-reading software to use the computer, and techniques for performing life skills and academic tasks from the teacher of students with visual impairments and orientation and mobility specialist. Better yet, your child should begin learning the aforementioned accommodations in preparation for complete loss of sight.
Resources for Families of Children with Cone-Rod Dystrophy