Achromatopsia is the abnormality or absence of retinal cones. There is a complete and incomplete form. Achromatopsia is a rare hereditary vision disorder which affects 1 person in 33,000 in the U.S. Someone with achromatopsia has little or no cone cell function in the retinas of their eyes. Cone cells permit color vision, perception of fine detail, and the ability to adapt to all higher levels of illumination. Cones provide "day vision."
Signs and symptoms: Vision is worse in bright light. Eye function is markedly better in reduced illumination.
Characteristics: visual acuity about 20/200 in complete form. Basically normal retina, or definite macular abnormality. Nystagmus is present. Total lack of color discrimination is pathognomonic. The cone ERG is absent as is the first portion of the scotopic red response in both the complete and incomplete forms. In children wiht poor acuity, nystagmus,, and a normal fundus, who are too young to treat, the ERG assumes a major role in differential diagnosis. In the incomplete forms of congenital cone blindness, the acuity range is better (20/40 to 20/100); there may be misleading and may be diagnosed as macular degeneration or ocular albinism. In these cases, the ERG is essential for confirming the diagnosis.
Prognosis: nonprogressive. Vision remains relatively good in subdued light. Nystagmus and photophobia improves with age.
Lighting: Bright light and glare should be avoided: Reduced illumination especially when reading is preferred