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| The Surgical Technologist | SEPTEMBER 2018 400 attached to the retina behind it. The lens focuses the light through the vitreous fluid and onto the retina. The retina is a thin, semi-transparent, light-sensitive layer that lines the posterior wall of the eye. The portion of the posterior wall that is not lined by the retina is the small area where the optic nerve enters the eye. Photoreceptors in the retina convert light into nerve impulses. Nerve fibers within the retina send these impulses to the brain, via the optic nerve, which interprets them as a visual image. 3 Directly behind the retina is the choroid. The choroid contains blood vessels, which help supply blood and oxy- gen to the retina. The choroid also contains a dark-colored melanin pigment. This pigment absorbs excess light and prevents light reflection in the eye that would otherwise cause blurred vision. 1 The choroidal pigment gives the back of the eye its red/orange color, and it is what causes “red eye” when flashed pictures are taken. It is this pigment layer of melanin-producing cells in the choroid that can develop melanoma. The iris and ciliary body also contain melanin and also can develop ocular melanoma. C H O R O I D A L M E L A N O M A C A U S E S DNA is the chemical in our cells that makes up our genes. Genes control how our cells function. Some genes control when our cells grow, while others control cell division and death. Genes that help cells grow, divide and stay alive are called oncogenes. Genes that cause cells to die at the right time are called tumor suppressor genes. Sometimes, errors develop in the DNA of healthy cells and cause mutations in the cells’ genes. If damaged DNA causes the mutations to occur in tumor suppressor genes, the mutated cells continue living when they would normally have died. When the cell divides, these mutations are passed to a new generation of cells. The rate of cell division in the mutation-bearing cells can then become uncontrolled.When these mutations occur in melanocytes in the choroid, it can cause choroidal mela- noma. These rapidly dividing melanocytes accumulate in the choroid of the eye and lead to the formation of a tumor. Exposure to ultraviolet (UV) rays damages the DNA of healthy melanocytes in the skin and can increase the risk of developing skin melanoma. However, it is not yet known whether there is any link between UV ray exposure and the development of choroidal melanoma, as no study has proven a direct linkage. As with many other forms of cancer, the exact cause of these DNA errors in choroidal melanoma is unknown. Choroidal melanoma is a primary intraocular malignant tumor and is not caused by a metastasized skin melanoma. Figure 2 Choroidal melanoma tumor photographed with an ultra-wide field fundus camera WilliamYatesCRA,COT,UCHealthdiagnostics