What is ocular melanoma
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. Conjunctival melanoma arises in the transparent membrane lining the white outer surface of the eye, the inner surface of the eyelids and the caruncle (the fleshy tissue over the white of the eye nearest the nose).
Ocular melanomas are rare, developing in about six people per million per year, or about 2000 persons in the United States each year. These tumors represent approximately one twentieth (i.e., 5%) of all melanomas in the body. Only one-in-fifty of all ocular melanomas are conjunctival, almost all being uveal. 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. Sunlight is believed to cause some conjunctival and iris melanomas. 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.
Most uveal melanomas are treated with some form of radiotherapy, which is usually administered with a radioactive implant, known as a plaque, or with a proton beam. A few can be surgically removed, either whole or in fragments. Some very small melanomas are treated with laser. Removal of the eye (enucleation) s performed only when such treatments are unlikely to conserve a comfortable and seeing eye. Conjunctival melanomas are usually treated by surgical removal, which in some centers is followed by radiotherapy to prevent the tumor from coming back. Flat melanomas confined to the conjunctival surface are often treated with chemotherapy drops. Very rarely, advanced conjunctival melanomas require removal of the eye and surrounding tissues (exenteration). The chances of saving the eye and vision vary greatly, depending on the size, location and extent of the tumor. Side effects, such as fluid leakage from an irradiated tumor, may require repeated treatment. Regular examinations are necessary to detect and treat any recurrent tumor without delay.