Melanomas are cancerous tumors arising from melanocytes, which are cells that produce melanin, a brown pigment that absorbs light. Ocular Melanomas comprise uveal and conjunctival melanomas. Uveal Melanoma, or UM, develops within the uveal tract, which comprises the choroid, the ciliary body and the iris. The choroid is a cup-shaped tissue under the retina. The ciliary body is a muscular ring that adjusts the focus of the lens, to maintain clear vision. The inner lining of the ciliary body pumps fluid into the eye to maintain the shape of the eyeball. The iris adjusts the size of the pupil, regulating the amount of light reaching the retina. Ocular melanomas are rare, developing in about six people per million per year, or about 2500 persons in the United States each year. These tumors represent approximately one twentieth (i.e., 5%) of all melanomas in the body. About nine-out-of-ten uveal melanomas are choroidal, the rest originating in ciliary body or iris. Intraocular melanomas are the most common form of cancer arising in adult eyes.
Ocular melanomas are most common in individuals with white skin and blue eyes. Some uveal melanomas arise from moles or, rarely, in individuals inheriting the ‘BAP1 cancer predisposition syndrome’. Similarly, conjunctival melanomas may develop ‘out from nowhere’ or from moles or from brown areas in the conjunctiva called ‘primary acquired melanosis’. Ocular melanomas almost always present in adulthood, especially around the age of 60 years. Men and women are affected in equal numbers. Whereas conjunctival and iris melanomas are visible to the naked eye, detection of choroidal and ciliary body melanomas requires ophthalmoscopic examination, usually performed by an optometrist or ophthalmologist. The most common symptoms of uveal melanomas at the back of the eye are blurred vision, blind-spots, and seeing flashing lights.