Abstract
Colour vision deficiencies (CVDs) can be categorised as being congenital or acquired. Some CVDs are already present at birth, as inherited conditions that are the result of changes at the photo-pigment level and are non-pathological, incurable and do not change over time. Examples are red-green defects which are inherited as an X-linked recessive trait. Acquired CVD develops secondary to ocular and systemic conditions or as a side effect of certain medications or sometimes toxic effects of chemicals, and trauma and ageing can also be important in some CVDs.
Highlights
Colour vision is the ability of an organism to distinguish objects based on the wavelengths of the light they reflect, emit or transmit.[1,2] A person’s perception of colours is a sensitive and subjective process whereby the brain responds to the stimuli that are produced when incoming light reacts with the several types of photoreceptor cells in the retina and signals are sent through to the occipital cortex of the brain.[3]
Congenital colour deficiencies are caused by inherited photo-pigment abnormalities and reasons for an acquired Colour vision deficiencies (CVDs) may be ocular pathology, intracranial injury, excessive use of therapeutic drugs or unintentional drug exposure
Acquired CVDs have been classified in a way similar to congenital CVDs, with two types of protan–deutan deficiencies (Type 1 and Type 2) and one type that has tritanlike defects of colour (Type 3)
Summary
Colour vision is the ability of an organism to distinguish objects based on the wavelengths (or frequencies) of the light they reflect, emit or transmit.[1,2] A person’s perception of colours is a sensitive and subjective process whereby the brain responds to the stimuli that are produced when incoming light reacts with the several types of photoreceptor cells in the retina and signals are sent through to the occipital cortex of the brain.[3]. There are three types of cones that have overlapping peak spectral responsivities. They are the long-wavelength cones (L-cones), which have a peak sensitivity at approximately 560 nm corresponding to a greater sensitivity to red; the medium-wavelength cones (M-cones), which are maximally responsive to green at 530 nm; and the short-wavelength cones (S-cones); which have a peak sensitivity at 430 nm that relates to colour sensitivity to blue.[5] the overlap between these three spectra of absorption allows the brain to discriminate colour on the basis of wavelength, providing comparisons of photon absorptions by the different cones.[6] The sensitivity of this colour sense, increases the susceptibility to colour defects that may occur because of toxins, or ocular or systemic disease.[7]
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