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Webvision: Color Perception Page 12 of 18 <br />tritanopia was originally established by family studies (eg, Henry et al., 1964; Cole et al., 1966; Smith et <br />al 1973) and subsequently confirmed by molecular genetics (Nathans et al., 1986a,b). <br />Using he CIEiagram, to Develop Diagnostic Colour I <br />Vision Festa <br />Discrimination of colour by dichromats is limited due to one photopigment being absent. <br />Therefore, when it comes to colour matching, certain colours are confused with another. Confusion lines <br />are lines joining points on the chromaticity diagram that appear the same in colour for dichromats. The <br />number of confusion lines also provide information about the amount of change in wavelength (A 1) <br />before another colour is discriminated (when the next confusion line is met). All confusion lines <br />converge to a point called the copuntal point (figure 18). <br />Fjctire 18. Schematic of herr cnnfiision lines !taC iza.� tt7e copune=al point and A i. z'or�� protann—,). 23 K ine_grgagQ <br />In figure 19 show the confusion lines for a protanope and a deuteranope. There are 17 confusion lines <br />for a protanope and 27 confusion lines for a deuteranope. Therefore, deuteranopes can discriminate more <br />colours because smaller changes in wavelength (A l steps) can be discerned. Figure 20 shows the <br />confusion lines for the tritanope. <br />1937 from Le Grand, Y., Light, Color and Vision. 2n`'' ed. London: Ch. man <br />aad Hall 196558}_(,91>,j. eg image} <br />http://www.webvision.med.utah.edu/KallColor.html <br />Fizszre 20. Confusion lines for a trifznope(from .Benjamin, td%_ J. <br />(Ed). Borish's Clinical Refraction. Philadell)hia_�t'. B. Saunders <br />6/18/01 <br />