The retina is the transparent, light-sensitive structure at the back of the eye. Cancers affecting the retina usually occur in the choroid, a dense layer of blood vessels that supplies the retina. The choroid is sandwiched between the retina and the sclera (the outer white layer of the eye). Because the retina depends on the choroid for its support and half of its blood supply, damage to the choroid by a cancer is likely to affect vision.
Choroidal melanoma is a cancer that originates from the pigment-producing cells (melanocytes) of the choroid. Choroidal melanoma is the most common cancer originating in the eye. It is most common among whites. It occurs most frequently at age 55 to 60.
In its early stages, the cancer usually does not interfere with vision. Later, it may cause blurred vision or retinal detachment, with symptoms such as flashes of light, a veil or curtain across the visual field, or a sudden increase or change in floaters (objects that appear to move through a person's field of vision). Melanomas, particularly if large, may extend into the orbit or spread through the bloodstream (metastasize) to other parts of the body and may be fatal.
Choroidal metastases are cancers that have spread to the choroid from other parts of the body. Because of its rich blood supply, the choroid is often a place to which cancers from other parts of the body may spread. In women, breast cancer is the most common cause. In men, cancers of the lung and prostate are the most common causes.
Often, choroidal metastases cause no symptoms until they are advanced. Symptoms, when they develop, are often loss of vision or symptoms of detachment of the retina such as floaters, flashes of light, blurred vision, and a veil or curtain across the field of vision. Vision loss can range from mild to severe.
The diagnosis of choroidal metastases is sometimes made during a routine eye examination with an ophthalmoscope. The diagnosis is aided by ultrasonography.
Confirmation of the diagnosis may involve using a fine needle to remove a sample of tissue for examination under a microscope (biopsy).