Contributor: Gordon K. Klintworth
Heterochromia iridis occurs in several conditions (including Waardenburg syndrome, Fuchs heterochromic iridocyclitis, melanosis oculi, iris melanoma [melanoma - iris] and Horner syndrome). The iris may be excessively pigmented (as in melanosis oculi,, a primary iris melanoma or an iris that has been invaded by a melanoma from the ciliary body [melanoma - ciliary body]. In some of conditions, such as Waardenburg syndrome, the heterochromia can be segmental and only involve part of the iris. In Horner syndrome the iris is ligher than normal on the affected side. Because the iris originally has a normal color Horner syndrome illustrates that an intact sympathetic innervation of the iris is important in the maintaining iris pigmentation. Certain drugs, such as latanoprost [latanoprost complications] can also make the iris darker than normal.