What is Achromatopsia?
Achromatopsia is a retinal condition that results in the inability to see color. Complete achromatopsia prevents a person from seeing color; they only see black, white, and varying shades of gray. Individuals with incomplete achromatopsia, a less severe type, may have some color vision.
Achromatopsia is a rare autosomal recessive inherited retinal disorder that affects 1 in 30,000 individuals. Other symptoms include light sensitivity, reduced vision, and uncontrolled eye movements.
- Achromatopsia is a disorder of the cones that make up the retina, which sends visual signals from the eye to the brain.
- Retinal achromatopsia occurs when both parents carry a copy of the mutated gene.
- The condition can be inherited genetically or acquired due to brain damage.
A process known as phototransduction is responsible for sending visual signals from the retina of your eye to your brain. The retina is made of two different classes of light-receptor cells called rods and cones. Rods function in low light vision, such as at night, and cones are responsible for color vision, and visual acuity/clarity.
If the cone cells malfunction, they lose their ability to signal to the brain. This limits the process of phototransduction.
There are two types of achromatopsia, total and incomplete. With complete achromatopsia, the cone cells do not function, and signals are only transferred through rod cells. In this case, you would experience severe visual problems.
With incomplete achromatopsia, also called rod monochromacy, you retain some cone cell function and experience less vision issues.
Achromatopsia differs from more common forms of color blindness by the fact that all three types of cones are defective.
Achromatopsia is inherited when an individual acquires two copies of the defective gene—one from each parent. In this case, the defective gene is present in both of your parents, though they normally do not exhibit the signs and symptoms of the disorder because their functional or “good” gene helps balance out the defective gene. However, when those parents have a child, that child may get a defective gene from both parents.
In most circumstances, a person who gets one normal gene and one defective gene will not have visual symptoms, but will just be a carrier. A carrier means you are carrying a defective copy of the gene but do not have the condition yourself.
Cerebral achromatopsia is an acquired color blindness. Causes include brain damage from trauma, tumors or infections.
Symptoms of achromatopsia begin to show up during the first few months of life and can include:
- Reduced visual acuity
- Photophobia (light sensitivity)
- Hemeralopia (day blindness)
- Nystagmus (uncontrolled eye movements)
- Lack of color discrimination
At this time, there is no proven treatment for achromatopsia. However, there are tools available to help you manage visual impairment, including magnifiers for poor vision and deep red-tinted glasses or contact lenses to lessen symptoms of light sensitivity.