THE COLOR OF THE HUMAN EYE - A REVIEW OF MORPHOLOGIC CORRELATES AND OF SOME CONDITIONS THAT AFFECT IRIDIAL PIGMENTATION

Iris color can be affected by a variety of ocular disorders. It is sus pected that iris color may not remain constant throughout life. These observations have drawn attention to the morphologic correlates of iri s color and its regulation. Differences in the iris color of normal ey es are the result of variable amounts of melanin pigment granules with in a constant number of melanocytes in the superficial stroma of the i ris. These melanocytes seem to reach their genetically determined amou nt of melanin in early childhood, and their melanin content usually re mains constant in adulthood. Diseases such as Horner's syndrome and Fu chs' heterochromic iridocyclitis affect iris color, resulting in a dec rease of iris pigmentation. Evidence suggests that melanin content of some melanocytes is subject to adrenergic regulation even past childho od. Application of the prostaglandin analogue latanoprost, on the othe r hand, leads to an increase in iris pigmentation in some patients. St udies with cultured dermal and uveal melanocytes, as well as with weal melanoma cells, however, show no increase in cell proliferation when treated with latanoprost in vitro. The mechanisms by which latanoprost affects regulation of iris pigmentation requires further investigatio n.