Eye cancer, medically known as ocular cancer, is a condition arising from the uncontrolled growth of cells within the eye or the surrounding tissues. Compared to other forms of cancer, this disease is rare, with only a few thousand new cases diagnosed annually in the United States. Eye cancer begins when malignant cells form a tumor inside the eyeball. Like other cancers, these tumors can spread to other parts of the body if not treated early.
Primary Types of Ocular Cancer
The most frequently diagnosed primary eye cancer in adults is uveal melanoma, which develops in the uvea, the middle layer of the eyeball. This layer contains pigment-producing cells called melanocytes, which are the source of the cancer. The choroid, a vascular layer situated between the retina and the outer wall of the eye, is the most common site for uveal melanoma formation. Tumors that begin in the iris, the colored part of the eye, tend to be slower-growing and are typically diagnosed earlier because they are visible as a dark, growing spot. Less frequently, the cancer can form in the ciliary body, which contains the muscles that help focus the lens.
In children, retinoblastoma is the most common form of eye cancer, usually affecting those under the age of five. This cancer starts in the retina, the light-sensitive tissue at the back of the eye. Retinoblastoma is caused by a genetic mutation that causes nerve cells in the retina to grow and multiply uncontrollably.
Primary intraocular lymphoma (PIOL) is another type of cancer that originates within the eyeball, though it is less common than uveal melanoma. This form involves the body’s white blood cells (lymphocytes) and is often a type of non-Hodgkin B cell lymphoma. PIOL frequently affects the elderly or those with weakened immune systems and may occur simultaneously with lymphoma in the central nervous system.
Recognizing the Signs
Eye cancer can progress without causing noticeable symptoms in its early stages, especially if the tumor is small or located away from the central vision area. When symptoms appear, they relate to a disturbance in vision or a physical change in the eye’s appearance.
The most common signs include painless loss of vision (partial or total) or the sudden onset of blurred or distorted sight. Patients often report seeing new or increased numbers of floaters, which are spots or squiggly lines that drift across the field of vision, or flashes of light.
Other indicators include a visible dark spot on the iris that appears to be growing larger, changes in the size or shape of the pupil, or a change in the color of the iris itself. Less common symptoms include a bulging of the eye or a noticeable mass growing on the eyelid or eyeball surface. Persistent irritation or redness that does not improve should prompt a visit to an eye specialist.
Diagnosis and Staging
Diagnosis begins with a comprehensive eye examination performed by an ophthalmologist. A dilated fundus examination allows the doctor to view the back of the eye, including the retina and choroid, where most tumors develop.
Imaging techniques are then employed to accurately measure the tumor and assess its location. Ocular ultrasound provides detailed images of the internal structure of the eye and is effective for measuring tumor size and shape. Magnetic Resonance Imaging (MRI) and Computed Tomography (CT) scans determine the tumor’s size and whether it has spread outside the eye into surrounding tissues or distant organs. In rare cases, a biopsy may be performed to obtain a tissue sample for laboratory analysis to confirm the cell type.
The cancer is then staged to describe its extent, which guides treatment decisions. The TNM (Tumor, Node, Metastasis) system classifies the cancer based on the size of the primary tumor, spread to nearby lymph nodes, and metastasis to distant sites. For uveal melanoma, a simpler system based on the Collaborative Ocular Melanoma Study (COMS) classifies tumors as small, medium, or large based on thickness and width.
Treatment Approaches
Treatment depends on the type of cancer, its size, location, and the patient’s overall health. For many eye cancers, particularly uveal melanoma, radiation therapy is the most common approach. This method is highly effective at preserving vision.
Radiation can be delivered via two primary methods:
Plaque Therapy
This form of brachytherapy involves surgically placing a small, disc-shaped device containing radioactive seeds directly onto the outside of the eye over the tumor. The plaque remains in place for several days, delivering a concentrated dose of radiation.
External Beam Radiation
Techniques like proton beam radiation use a machine to direct highly focused beams of radiation at the tumor from outside the body.
Surgery may be necessary for larger tumors or those that have not responded to radiation. Surgical options range from local resection, which removes the tumor and a margin of healthy tissue, to enucleation, which is the removal of the entire eyeball.
Systemic therapies, including chemotherapy, targeted therapy, and immunotherapy, are reserved for specific types of eye cancer or when the disease has spread beyond the eye. For retinoblastoma, chemotherapy may be used to shrink the tumor before other treatments are applied. Immunotherapy, which helps the immune system recognize and destroy cancer cells, is an option for treating metastatic uveal melanoma.