Achromatopsia is an inherited disease that causes reduced visual acuity, an inability to see well in bright light, and the inability to see color.
The eyes have two types of photoreceptor cells: rod cells and cone cells. Cone cells function best in bright light and allow us to perceive color and fine detail. Rod cells, on the other hand, function best in low light and are responsible for our 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. 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 colorblind 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 and completely without color.
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. Please note that Counsyl does not test for this form of the disease.
People with achromatopsia often experience a vibration or rapid oscillation in their field of vision, a symptom known as pendular nystagmus.
Symptoms of achromatopsia do not worsen over time and do not typically lead to blindness.
Several genes can cause achromatopsia. The gene for which Counsyl tests, CNGB3, is most commonly reponsible for achromatopsia, causing 50% of known cases. Mutations in CNGB3 have also been observed in a small number (approximately 5%) of patients with progressive cone dystrophy, a disease that can be confused with achromatopsia.
Achromatopsia affects roughly 1 in 33,000 Americans. It is most common on the remote atoll of Pingelap in Pohnpei, part of the Federated States of Micronesia in the Western Pacific. There the disease affects 4 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.
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 4-10% of the population has achromatopsia.