Human color vision is generally trichromatic, based on the responses of three types of cones—L, M, and S cones in the retina—each with a peak sensitivity in different wavelength regions of visible light. However, it is also known that human color vision exhibits diversity. There are individuals with color deficiencies referred to in medical terminology as dichromacy or anomalous trichromacy as typical representatives of color vision diversity. A defining characteristic of these color vision types is the existence of color combinations that are indistinguishable. Consequently, in the past, these types of color vision were referred to as color blindness, and individuals with color deficiencies faced restrictions in higher education and employment, making them targets of discrimination. Furthermore, based on these factors, dichromacy has been regarded as a disadvantageous type of color vision. However, it has also been reported that dichromacy does not necessarily pose a disadvantage in all functions performed by color vision. For example, Morgan et al. (1992) and Saito et al. (2006) reported that, in camouflaged patterns, dichromats are less affected than trichromats by chromatic noises, giving them an advantage in detecting target patterns. In this paper, I am introducing color vision diversity and the advantages of dichromacy.

This study investigated the effects of base-in prism (BIP) lenses on visual fatigue during near vision tasks, using fusion sustainment ability as an objective parameter and the Symptom Questionnaire (SQ) as a subjective parameter. The results showed that, compared to regular near lenses, BIP lenses significantly reduced visual fatigue, as indicated by improved fusion sustainment ability and lower SQ scores. The addition of base-in prism components to near lenses was found to support not only accommodation but also convergence, suggesting a potential benefit in reducing eye strain during near vision, particularly for Japanese individuals who are prone to near exophoria.