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GCSE Biology · key term
A colour vision deficiency in which a person cannot distinguish certain colours in the usual way because one or more types of cone do not respond normally.
Used by Edexcel and OCR
Specification 2.16B · Paper 1
Revise: Eye DefectsIn colour blindness, also called colour vision deficiency, a person may lack a normally functioning cone type or produce an altered cone pigment. Consequently, some colours that most people see as different produce responses that are too similar to distinguish reliably.
Specification B3.1e · Paper 1 (Foundation), Paper 3 (Higher)
A vision defect in which a person has difficulty distinguishing particular colours because one or more types of cone cell are absent or do not function normally.
Revise: Eye defectsIn colour blindness, one or more types of cone are absent or do not respond normally. The signals reaching the brain therefore make some colours difficult to distinguish. Red–green colour blindness is a common example.
Colour blindness affects colour detection by cone cells, not the eye's ability to focus light. It usually causes difficulty distinguishing particular colours rather than completely colourless vision.
When describing colour blindness, avoid saying that a person necessarily sees only in black and white. The usual effect is difficulty distinguishing particular colours.
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