Aquired Heterochromia - Complete - Most common of the three, heterochromia iridium is a condition where one iris is a different color than the other. In this particular illustration, the affected iris (shown) is hypochromic, in which the iris tissue exhibits a lack of pigmentation in comparison to the normal iris. This can be caused by Fuchs’ heterochromic iridocyclitis, Acquired Horner’s syndrome, Neoplasm, or Chronic iritis.