Color Blindness - Tritanopia essays

Color Blindness - Tritanopia essays Colour Blindness, defect of vision affecting the ability to distinguish colours, occurring mostly in males. Colour blindness is caused by a defect in the retina or in other nerve portions of the eye. Partial colour blindness, called dichromatism, consists generally of the inability to differentiate between the reds and the greens or to perceive either reds or greens; infrequently, the confusion may involve the blues or the yellows. Dichromatism is the most common form of colour blindness, affecting about 7 percent of men and less than 1 percent of women. Dichromatism is identified as a sex-linked hereditary characteristic (Figure 1). A colour blind person has difficulty in distinguishing colours that are on "confusion lines". For example, protanopes confuse blue-greens (and greys) with red (and browns). The deutranopes make mistakes with blue-greens and purple. While tritanopes confuse yellow with blue. The last dichromat group; tetartanopes, confuse yellow with blue. The anomalous types have difficulty with light tints and dark shades. Tritanopia is rare, affecting one in fifty thousand males and one in one hundred thousand females. There are three different types of wave sensitivity cones: long (red), medium (green), and short (blue). Short wave sensitivity (SWS) cones are most sensitive to a wavelength of approximately 419nm. When examining the absorbance curve, long and medium wave sensitivities are close together (30 nm shift), whereas the SWS cone curve is shifted more than 100 nm away S cones are much rarer than long and medium cones, accounting for approximately 5% of the total. When our vision depends on SWS cones alone, our spatial resolution is very poor. Tritanopes have malfunctioning SWS cones. The problem occurs when there is a dominant inheritance of the G79R and S214P mutations this suggests that the abnormal gene products actively interfere with the viability or accuracy of blue ...