Similar to Tritanopes

Similar to Protanopes

Figure 13 These spots of color appear different to subjects with color deficiencies. Normal subjects see the spot on the left most similar to the central spot. Deuteranopes see the upper, protanopes the right, and tritanopes the lower spot as most similar to the central spot.

Figure 14 A pseudoisochromatic plate that detects protanopes, deuteranopes, and tritanopes, who fail to see the blue square at the upper right side. (See color insert in Volume 1).

Such color deficiences can also be detected by the use of plates in which spots of different colors that confuse defective subjects are arranged in different sizes so that a figure can be seen by normal subjects but not by defective ones and sometimes vice versa. One that detects both red-green and blue-yellow defective vision is shown in Fig. 14.

Defects in the S cone opsin located on chromosome 7 are rare. They are usually autosomal-dominant mutations. Such subjects are called tritanopes and have only red-green color vision. They retain high spatial resolution. A pseudoisochromatic plate that detects tritanopia is shown in Fig. 15.

Interestingly, there is no gene defect that produces achromatopsia without decreasing acuity, but the converse frequently occurs, including virtually all disorders of the macula.

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