Achromatopsia is characterized by the absence or deficiency in the functioning cones. This leads to reduced visual acuity, pendular nystagmus, photophobia, and mild or complete loss of color discrimination.
All individuals with achromatopsia have altered color discrimination in the three axes corresponding to the three classes of cones. Most individuals have complete achromatopsia, with a complete absence of function of all three types of cones. Rarely do individuals have incomplete achromatopsia, in which one or more types of cones may partially function. Although the fundus is usually normal, in some affected people, there may be macular changes and narrowing of blood vessels.
The prevalence of the disease is estimated at 1/30,000 individuals globally.