An impairment in the ability to perceive colours. Most commonly due to a defect in the cone photoreceptors in the retina, inherited through the mother (X-linked) so that men are affected (8%) and women are generally unaffected carriers (only 0.4% affected). Very rarely, inherited cone dystrophies may impair colour perception.
Colour vision disorders may also result from damage to the optic nerve (optic neuropathy) or diseases affecting the macula
Clinical Features
Inherited forms most commonly cause difficulty discriminating red and green
Optic neuropathy often leads to loss of red perception first
Management
Inherited colour blindness does not affect the holding of a driving license but does disbar from certain professions
Any new loss of colour perception needs referral to an ophthalmologist
