Achromatopsia: When You See No Colors at All

What is achromatopsia?

In achromatopsia (also called rod monochromacy) the cones in the retina do not work, or barely work. Vision is handled almost entirely by the rods – the cells normally used for seeing at dusk. Rods cannot distinguish colors, so people see the world in shades of gray and brightness.

Symptoms of achromatopsia

Because cones are also responsible for sharp vision and seeing in bright light, achromatopsia usually shows in infancy through:

• strong light sensitivity (photophobia) – bright daylight is very uncomfortable,
• nystagmus (involuntary eye movements), often noticed in the first months of life,
• low visual acuity, often around 20/200,
• absent color vision.

In incomplete achromatopsia, some color vision and slightly better acuity remain.

Causes and how common it is

Achromatopsia is inherited in an autosomal recessive way: a child is affected when it inherits an altered copy from both parents. Known genes include CNGA3 and CNGB3. It affects about 1 in 30,000 people, men and women equally.

There is also a very rare acquired form, cerebral achromatopsia, in which brain damage (for example a stroke) disrupts color processing.

Diagnosis

Nystagmus and light sensitivity in a baby are early clues. Eye doctors confirm the diagnosis with color vision tests, a measurement of retinal function (electroretinogram, ERG) and genetic testing. A simple Ishihara test shows that color vision is missing, but cannot distinguish achromatopsia from other types.

Aids and research

• Filter glasses (often red or dark tinted) greatly reduce glare.
• Magnifying aids help with reading and school.
• Early intervention and counseling support children and parents.

Gene therapy trials have been carried out for CNGA3 and CNGB3. There is no approved treatment yet.

How it differs from other color blindness

Most "color blind" people do not have achromatopsia but red-green color blindness or, less often, blue-yellow color blindness. They see colors, confuse certain shades – and have normal sharpness of vision. An overview of all types: color blindness.