Which type of color vision deficiency is characterized by the absence of the red photopigment?

The type of color vision deficiency characterized by the absence of the red photopigment is known as Protanopia. Individuals with Protanopia have a genetic condition resulting from a mutation on the X chromosome, which affects the photopigments in the cones of the retina that are responsible for detecting red wavelengths of light. This absence leads to difficulties in perceiving red colors and can also affect the perception of greens and other colors due to the overlap in the wavelength detection of the other photopigments.

This condition affects color discrimination, particularly where red and green colors blend, often leading to confusion between these two color families. In contrast, the other types of color vision deficiencies involve different photopigments or mechanisms. For example, Deuteranopia is related to the absence of the green photopigment, Tritanopia pertains to the absence of the blue photopigment, and Anomalous trichromacy involves a partial deficiency that does not result in a complete absence of any of the photopigments, making the perception of color less affected than in Protanopia.

Overall, Protanopia specifically identifies the loss of red sensitivity, making it the correct answer in this context.