Achromatopsia Report

Achromatopsia is a rare retinal alteration, transmitted in an autosomal recessive manner and characterized by partial or complete color blindness, photophobia, nystagmus (involuntary and repetitive movements of the eyeballs) and severe reduction of visual acuity.
The mechanism of vision is extremely complex and involves, among other factors, two types of cells called cones and rods (photoreceptors).
The former are responsible for daytime vision and are concentrated in the center of the retina, in an area called macula. Thanks to the cones we are able to adapt to the various light intensities, perceive the colors and discriminate the details of the images. The rods, placed on the periphery of the retina, allow night vision, thanks to a very high sensitivity to light, but give rise to an achromatic vision (i.e. they do not allow to discriminate the various colors, but only the different shades of gray existing between black and white).
In subjects suffering from achromatopsia, mutations in the genes involved in phototransduction (i.e. in the conversion of the light signal into electrical) cause, in the cones, the loss of the ability to react to light stimuli and to perceive colors. Hence the typical color blindness, given by the fact that the vision will depend exclusively on the activity of the rods. This form of achromatopsia, the most severe, is defined as "complete". There are some "incomplete" forms, characterized by a residual functional activity of the cones and with milder symptoms, although the number of cones still functioning is highly variable from person to person.
Achromatopsia is estimated to affect one in 30,000 people, so it can be considered a rare condition.