tritanopia

   Also known as blue-yellow colour blindness, tritan colour blindness, and tritan colour deficiency. The term tritanopia comes from the Greek words treis (three), an (not), and opsis (seeing). It translates roughly as 'not being able to see the third of the primary colours' (i.e. blue). It is used to denote a type of "colour vision deficiency characterized by an inability to discriminate between blue and green, and between yellow and violet. Tritanopia is a rare condition, whose lifetime prevalence is estimated at around 1:10,000. Etiologically, it is attributed to an autosomal disorder linked to chromosome 7. As a consequence, the condition affects males and females in equal measure. Due to this chromosomal anomaly, the short-wavelength cones (or S-cones) in the retina are missing. As a consequence, the resulting colour vision deficiency is absolute. When the S-cones are present but malfunctioning, the colour vision deficiency may be relative rather than absolute. It is then referred to as "tritanomaly. Tritanopia is classified as a "dichromatism, which itself constitutes one of the colour vision deficiencies. The term tritanopia is used in opposition to the terms "protanopia and " deuteranopia.

   References

   Hsia, Y., Graham, C.H. (1965). Color blindness. In: Vision and visualperception.Edited by Graham, C.H. New York, NY: Wiley. McIntyre, D. (2002). Colour blindness. Causes and effects. Chester, PA: Dalton Publishing.