Definition:

Blue cone monochromacy (also known as X-linked recessive incomplete achromatopsia) is a congenital stationary cone dysfunction syndrome characterized by the absence of both red and green cone sensitivities. Vision is derived from the remaining blue cones and rod photoreceptors. Patients present with reduced visual acuity, pendular nystagmus, and photophobia. The prevalence of blue cone monochromacy is estimated to be 1 in 100 000 males.