Increment thresholds in tritanopia

Foveal increment threshold curves for two tritan obscrcers are reported. One of the tritans is a dichromat; the other is genetically a tritanope but has anomalous trichromatic color vision. The hypothesis was proposed that the complete tritanope would not demonstrate any of the three "blue" mechanisms (π₁, π₂, π₃) but that for the incomplete tritanope one or more of these mechanisms would be evident. No curve inflection which could be attributed to a "blue" mechanism was elicited for either tritan, indicating that these mechanisms are absent or have severely depressed sensitivity. The tritan's "green" π₄ mechanism has normal sensitivity at 580 nm and 480 nm but seems to have greater than normal sensitivity at 445 nm.