What is eye cancer? Eye cancer is uncontrolled growth of abnormal cells in or around the eye that develop into a mass (tumor). Eye cancer is categorized as either primary, meaning it started in the tissues of the eye, or secondary, meaning that the cancer started somewhere else in the body and metastasized, or spread, to the eye. Secondary eye cancer is more common than primary eye cancer. Breast cancer and lung cancer are the most common types of cancer that can cause secondary eye cancer. The eye is made up of three main parts: the eyeball, the orbit (the eye socket, muscles, and nerves that surround the eyeball), and the adnexal structures (accessory structures, such as the eyelid and tear ducts). Primary eye cancers can develop in any of these three parts. When cancer starts in the eyeball, it is called primary intraocular cancer. The most common form of primary intraocular cancer in adults is melanoma, followed by lymphoma. Types of primary intraocular cancer and their typical location are described below: Melanomas develop in pigment-producing or color-producing cells, such as those in the iris of the eye. Retinoblastomas start in the retina (the light-sensitive tissue at the back of the eye). Retinoblastomas are the most common form of primary intraocular cancer in children (Source: NIH). When primary orbital or adnexal cancers occur in certain areas, such as the eye socket or eyelid, they take the form of bone, muscle, nerve or skin cancers. Primary eye cancer is an uncommon condition. In 2010, only 2,480 new cases of eye cancer were reported in adults in the United States. The majority of these cancers were melanoma (Source: ACS). Retinoblastoma occurs in approximately four out of 1 million children younger than 15 years in the United States and accounts for approximately 3% of cancers in this age group (Source: ACS). While primary eye cancer can occur in both males and females of any age, it is more likely to occur in certain age groups. Adult primary eye cancers occur most often in people older than 50 years. Retinoblastoma occurs most often in children younger than five years, with two-thirds of retinoblastoma cases occurring in children younger than two years of age. The exact cause of most primary eye cancers is not known, but retinoblastoma is the exception. Retinoblastoma occurs as both an inherited form, meaning it is passed from parent to child through a gene, and a noninherited form. The inherited form of retinoblastoma accounts for approximately 25% to 30% of cases (Source: ACS). In either situation, a specific gene mutation permits uncontrolled proliferation of primitive retinal cells. Treatment of eye cancer will depend on the type of cancer, the stage of the cancer, and other factors. Successful treatment of eye cancer is more promising when these cancers are found early, so it is important to have regular eye exams as recommended by your healthcare provider. Although eye cancer is rare, it can lead to life-threatening complications and death, especially if it is undetected and left untreated. Seeking regular medical care, including regular eye exams, offers the best chance of discovering eye cancer in its earliest, most curable stage. If you have eye cancer, following your treatment plan may help reduce your risk of serious complications. Seek prompt medical care if you have visual symptoms, including trouble seeing, loss of part of your field of vision, or seeing flashes of light, dark spots on your iris, spots, squiggles, or floating objects.