A malignant melanoma of the anterior uvea that tends to spread around the globe is called a ring melanoma. In most cases the tumor has invaded the iris, the ciliary body, and the chamber angle with its outlet channels. It is often impossible to determine the primary site, the growth having been located in the ciliary body,1,2 in the base of the iris,3 in the iridociliary junction,4 or in the endothelial cells of the chamber angle.5,6
Reese1 differentiates between a "true" ring melanoma and a "disseminated" ring melanoma: a true ring melanoma spreads within the confines of the ciliary body, while a disseminated ring melanoma spreads by diffuse implantation growth around the free surfaces of the chamber angle and over the anterior surface of the iris.
Rones and Zimmerman7 have provided evidence that many malignant melanomas of the anterior uvea are not detected early
MANSCHOT WA. Ring Melanoma. Arch Ophthalmol. 1964;71(5):625-632. doi:10.1001/archopht.1964.00970010641006