Trichromatic vs. Tetrachromatic vision, image by Dr. Klaus Schmitt, Weinheim, Germany.
The above image is a rough representation of trichromatic and tetrachromatic vision (i.e. human vs. bird/insect vision; the latter includes the ultraviolet spectrum).
There have been assumed (Claude Monet) and now confirmed (Alek Komar) cases of tetrachromatic vision occuring in human individuals suffering from either aphakia (lack of intraocular lens) or pseudoaphakia (replacement of)
In essence, the therapeutic process of restoring vision, can, in a percentage of the human population (Jameson et al., 2001; Rosh, 2006), lead to an accidental enhancement, restoring not only vision, but also granting tetrachromatic colour perception.