CNGB3-related achromatopsia is an inherited disease that causes reduced visual acuity, sensitivity to bright light (photophobia), the inability to see color, and in some cases a vibration or rapid oscillation in the field of vision (pendular nystagmus). Farsightedness is also common. These issues stem from improper functioning of certain cells in the eyes.
The eyes have two types of photoreceptor cells: rod cells and cone cells. Cone cells function best in bright light and allow for perception of color and fine detail. Rod cells, on the other hand, function best in low light and are responsible for night vision. Rod cells cannot perceive color and provide less visual acuity than cone cells.
In people with achromatopsia, cone cells do not function properly, leaving only rod cells for vision. Because rod cells do not function well in bright light, as the amount of light increases, visual ability in people with achromatopsia decreases. People with achromatopsia will also be color blind and will not perceive detail well. Most people with the disease have “complete achromatopsia,” meaning that none of their cone cells are functioning. Their vision is 20/200 or poorer without correction and color detection is completely lacking. Some people with the disease have some functioning cone cells, leaving them with incomplete achromatopsia. They may be able to see some colors and typically have vision of 20/80 or poorer without correction. In general, symptoms of achromatopsia do not typically result in complete blindness.
Several genes can cause achromatopsia, although mutations of the CNGB3 gene are the most common cause of the disorder. Mutations in the CNGB3 gene have also been observed in a small number (approximately 5%) of patients with progressive cone dystrophy. Unlike achromatopsia (also known as stationary cone dystrophy because symptoms do not worsen over time), people with progressive cone dystrophy develop similar symptoms to those with achromatopsia, but with a worsening of vision over time. Progression usually occurs gradually over several years and is variable in severity and age of onset.
Achromatopsia generally affects roughly 1 in 30,000 Americans, and approximately 50% of cases are attributed to mutations in the CNGB3 gene. However, achromatopsia due to mutations in the CNGB3 gene is most common on the remote atoll of Pingelap in Pohnpei, part of the Federated States of Micronesia in the Western Pacific where the disease affects 5 to 10% of the population.
There is no cure for achromatopsia, but people with the disease have found ways to adapt. Many people with achromatopsia have found that dark brown, red, or gray-tinted glasses help them see outdoors during the day or in bright indoor spaces. Tinted contact lenses may also be helpful.
Other low vision aids such as large type books or magnifiers may be helpful. Parents of children with the disease should work with their child’s school to make any necessary modifications to his or her learning environment.
Achromatopsia does not affect lifespan, nor does it affect any other system of the body. While the person will have poor eyesight, particularly in bright light, the disease is not progressive and will not lead to blindness. However, a small number of mutations in CNGB3 are associated with a different disease known as progressive cone dystrophy. This disease will cause a person's eyesight to worsen over time.
A resource center and active discussion board for individuals, families, and friends of people affected by achromatopsia.
An information network for individuals and families who are affected by achromatopsia and for professionals interested in the disease. The site offers free downloads of two books in PDF format, Understanding and Coping With Achromatopsia and Living With Achromatopsia.
A 1997 book by neurologist and author Oliver Sacks about Pingelap, the remote Pacific atoll where 5-10% of the population has achromatopsia.
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