Eye Cancer Overview
The eye is a slightly uneven ball that is about an inch wide. The front part of the eye includes the iris (the colored part), the cornea (a clear dome over the iris), the pupil (the black circular opening in the iris that lets light in), the sclera (the white part), and the conjunctiva (an invisible, clear layer of tissue covering the front of the eye, except the cornea). Most of the eye is filled with a clear gel called vitreous humor.
The lens is found behind the iris and pupil. It helps to focus light on the back of the eye. The ciliary body contains the muscles inside the eye that change the shape of the lens so that the eye can focus on near or distant objects. It also has cells that make aqueous humor, the clear fluid in the front of the eye between the cornea and the lens. The choroid is a thin, pigmented layer that lines the eyeball. It nourishes the retina and the front of the eye with blood. Light goes through the pupil and the lens to the back of the eye. The inside lining of the eye is covered by special cells that sense light. These cells make up the retina. The retina converts light into electrical signals. The optic nerve carries these impulses to the brain. The macula is a small sensitive area within the retina that gives central vision. It is located in the center of the retina and contains the fovea, a small depression or pit at the center of the macula that gives the clearest vision.
Cancer of the eye is a rare kind of cancer. It occurs when cells become abnormal and grow. These cells come together and form a growth of tissue, called a tumor. A tumor can be noncancerous (benign) or cancerous (malignant). If cancerous, the tumor cells can spread to other parts of the body (metastasize). One kind of cancer that can be found in the eye is called primary intraocular cancer. These are cancers that start inside of the eyeball. Melanoma is the most common primary intraocular cancer followed by primary intraocular lymphoma.
Melanomas of the eye are rare. They can develop in the iris (the colored area), just behind the iris in the structure controlling the shape of the lens (ciliary body), and the pigmented layer (the choroid) covering the eyeball behind the retina. Most eye melanomas are slow growing.
Melanomas of the eye are classified by their size: small, medium, and large tumors. There are also different types of melanoma cells found in the eye. Spindle-shaped cells tend to be a less malignant type of cell. Epithelioid cells are melanoma cells that look similar to skin cells and are more malignant. Treatment of melanoma of the eye varies depending on the size of the tumor and cell type.
Small tumors are usually closely followed by an ophthalmologist (a medical doctor who specializes in eye and vision care) using diagnostic tools such as a slit lamp and ultrasound or CT scan. Measurements of the tumors are taken and if the small tumors become large they may be treated the same way as medium and large melanoma tumors. Medium and large melanomas may be treated by removing the eye, also called enucleation, or by applying radioactive plaques (also known as brachytherapy). If the melanoma has spread outside of the eye to the surrounding bone, treatment may include surgery with radiation therapy. Large melanomas made up of epithelioid cells need to be treated soon after they are discovered as they may quickly spread to other parts of the body. The most common area of metastasis is the liver. Treatment for ocular melanoma that has spread to the liver may include chemotherapy or immunotherapy given directly into the liver. Patients may want to consider participation on a clinical trial. A clinical trial is meant to obtain information on new treatments for patients with cancer. It is important to discuss all options with your doctor and together decide which treatment is best for you.
Primary intraocular lymphoma, also called lymphoma of the eye, is another type of cancer that can start in the eye. Lymphoma is a type of cancer that starts in immune system cells called lymphocytes. It usually starts in lymph nodes. Lymphomas can also start in organs such as the stomach, lungs, and rarely, in the eyes. There are 2 main types of lymphoma: Hodgkin disease and non-Hodgkin lymphoma. Primary intraocular lymphoma is always a non-Hodgkin lymphoma. Most people with primary intraocular lymphoma are elderly or have immune system problems such as the acquired immunodeficiency syndrome (AIDS). Primary intraocular lymphoma is often seen along with lymphoma of the brain, known as primary central nervous system (CNS) lymphoma.
People with lymphoma of the eye may have some common symptoms. These include blurred vision and eye floaters. Eye floaters are spots in your vision and may look like black or gray specks, strings or cobwebs that drift around as you move your eyes. Some people also experience a decrease in vision. Pain can also occur but this symptom is rare. Lymphoma of the eye can begin with one eye and affect both eyes after several months.
Treatment of lymphoma of the eye depends on the size of the tumor and whether cancer cells have spread to other parts of the body. Treatment may include external beam radiation, chemotherapy, or both of these. Radioimmunotherapy (RIT), a combination of radiotherapy and immunotherapy, may also be a treatment option. Patients may want to consider participation on a clinical trial. A clinical trial is meant to obtain information on new treatments for patients with cancer. It is important to discuss all options with your doctor and together decide which treatment is best for you.
Glossary of Terms:
Slit lamp exam: The slit-lamp examination looks at structures that are at the front of the eye.
Brachytherapy: is a procedure that involves placing radioactive material inside your body. Brachytherapy is one type of radiation therapy that's used to treat cancer. Also called internal radiation.