What Is Bardet-Biedl Syndrome?
This is no longer termed “Laurence-Moon-Bardet-Biedl syndrome.” An individual can have either “Laurence-Moon syndrome” or “Biedl-Bardet syndrome,” both rare genetic disorders with overlapping characteristics.
Bardet-Biedl is a syndrome (set of related attributes) caused by a genetic mutation and characterized by the eye condition known as cone-rod dystrophy, in addition to a variety of features that may include abnormal weight gain in the trunk (and related health issues), extra fingers or toes (polydactyly), intellectual disability, developmental delay, kidney issues, speech problems, inability to smell, and genital abnormalities.
We will focus on the eye condition associated with Bardet-Biedl syndrome: 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. These are the rods which 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.
Individuals with cone-rod dystrophy as part of the syndrome Bardet-Biedl typically experience decreased sharpness of vision (not correctable with eyeglasses), poor night vision, loss of color perception, and blind spots within the peripheral (outlying) vision that eventually lead to total loss of peripheral vision.
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 Bardet-Biedl Syndrome Diagnosed?
As several characteristics of Bardet-Biedl syndrome are identified, a team of medical professionals will begin to piece together the puzzle and diagnose a child.
Regarding the eye condition associated with Bardet-Biedl, the first symptoms include decreased detailed vision which is not correctable with glasses as well as poor night vision. You may also notice light and glare hurting your child’s eyes and limiting 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.
Are There Treatments for Bardet-Biedl Syndrome?
There is currently no cure for Bardet-Biedl syndrome; however, surgery, hormone treatments, medication, and therapies will likely be recommended for the associated medical issues.
There is also 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 Bardet-Biedl Syndrome 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), and blind spots in the peripheral vision (scotomas), progressing to total peripheral field loss.
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) and use of a brimmed hat while outdoors as well as shutting blinds while indoors if glare is present.
An individual 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 utilizing a reverse telescope to see an entire image within the remaining field of vision. Additionally, the individual 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 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 Bardet-Biedl Syndrome
- Bardet Biedl Syndrome Family Association
- Bardet-Biedl syndrome by Genetics Home Reference
- Bardet-Biedl Syndrome by the National Center for Biotechnology Information
- Cone Dystrophy by the National Organization for Rare Disorders
- Cone-Rod Dystrophy by the Foundation Fighting Blindness
- Cone-Rod Dystrophy by Genetics Home Reference
- Retinitis Pigmentosa by the Foundation Fighting Blindness
- 2015 Top 10 Retinal-Research Advances documented by the Foundation Fighting Blindness