Eye cancer is a term used to refer to cancerous lesions that are malignant growths. Such growths arise from various parts of the eye or spread to surrounding structures. Other surrounding structures include the eyelids, conjunctiva, the front layer covering and outlining the white of the eye, the cornea, the iris (the colored part of the eye), the retina (light-sensitive tissue at the back of the eye), and the orbit (the bony cavity surrounding the eye). Eye cancer includes both primary cancers, which arise in the eye itself, and secondary cancers, which spread to the eye from other parts of the body. Primary eye cancers are much less common than other types of cancer, yet can be extremely dangerous and require relatively prompt diagnosis and treatment.
Types of eye cancer vary according to the location of the cancer's origin and the normal cells involved. The most common is ocular melanoma, which develops from melanocytes - such cells produce color in the eye. The uveal tract – the tissues comprising the iris, ciliary body, and choroid – are most commonly affected by ocular melanoma, but this form can also be found in the conjunctiva. Early detection of melanoma in the eye is usually not possible because it rarely shows any symptoms in the early stages, making it difficult to detect.
Retinoblastoma is another type of cancer that occurs in the retina, a sensitive medium at the back of the eyeball that senses visual stimuli and transmits them to the brain. It is diagnosed in childhood—under the age of five in most cases. Genetic mutations that alter retinal cell formation primarily cause it. Hereditary or sporadic retinoblastoma affects one or both eyes and is believed to be one of the rarest types of cancer. Although it is not common, it is important to identify it in children because the cancer usually grows rapidly and causes vision loss.
Apart from the above two cancers, there are also some other rare cancers of the eye, such as intraocular lymphoma, which is linked to both of the above. Intraocular lymphoma is a cancer that arises from the immune system's white blood cells, lymphocytes. Intraocular lymphomas primarily affect the vitreous humor (the gel-like inside the eye), and they can also invade the retina. Like other forms of eye cancer, it takes time for the patient to get an early diagnosis as symptoms such as blurred vision, floaters, and other vision changes can easily be attributed to other conditions.
There are also neoplasms that affect the orbit of the eye, either primary or secondary to bone or soft tissue cavities continuous with the orbital bone. These tumors grow from the many tissues found in the orbit, such as muscles, nerves, and bones. Orbital tumors can be further divided into two categories, primary or secondary. Primary orbital tumors are defined as benign or malignant neoplasms that originate from structures within the orbit. Secondary orbital tumors are those that result from the spread of cancer cells from other locations in the body, such as the breast, lung, or skin.
One of the key characteristics of eye cancer is the potential for metastasis: the spread of cancer cells from their original location to other areas of the body. Eye cancer can sometimes spread to draining lymph nodes or other distant organs — for example, the liver, lungs, or bones — particularly in cases of choroid or retinal involvement. This potential for eye cancer to spread, in some cases, makes it a particularly aggressive form of cancer, with prognosis dependent on parameters such as cancer type, site, and early detection.
The causes of eye cancer are sometimes not identified. In many cases, no definite cause is found. Certain risk factors are associated with the development of eye cancer. Individuals who have fair skin, light-colored eyes, and a genetic predisposition to eye cancer have a higher risk of developing eye cancer. In addition, environmental factors including exposure to ultraviolet (UV) light may contribute to increased risks of ocular melanoma. Patients with hereditary conditions such as retinoblastoma are at a higher risk of developing eye cancer. In addition, the development of eye cancer also depends on a few key factors including age, ethnicity, and gender, making it more common in some populations than others.
Eye cancer has different symptoms for different locations and types of cancer and of course how far the disease has progressed, but most cases do not have obvious symptoms when diagnosed. Eye cancer can grow too large to spread to other parts of the body before symptoms appear. Early eye cancer has mild symptoms like blurred vision, partial vision loss, and the occasional appearance of floaters in the field of vision; in some other cases, the person will notice a dark spot in the iris or a change in eye color. Cases of cancer affecting the orbit or other tissues around it will show obvious swelling, a significant bulge may develop in the eye as well as pain around it. As the eye cancer spreads to the brain and other organs, the symptoms worsen and even include headaches, nausea, and problems with coordination and balance.
The evaluation of eye cancer typically includes medical history, physical examination, and specialized imaging tests. The main step in diagnosing eye cancer begins with an ophthalmologist performing a detailed eye examination. This may involve a slit-lamp microscope for detailed vision, as well as specialized imaging techniques including ultrasound, optical coherence tomography (OCT), magnetic resonance imaging (MRI), and computed tomography (CT) scans. These imaging modalities are very important in determining the location, size, and extent of the tumor, as well as the stage of the cancer. Sometimes, a biopsy is performed to obtain tissue for laboratory diagnosis of the cancer, thereby identifying its type.
Upon diagnosis of eye cancer, treatment varies depending on the type and location of the cancer, its stage, and the general health status of the patient. Treatment may include surgery, radiotherapy, chemotherapy, or a combination of all three. The surgical approach is often the preferred option for small tumors or tumors located around the resection without affecting vision. Radiation therapy is often used to shrink or destroy malignant cells for tumors that are difficult to reach or located in critical areas. Brachytherapy, a type of radiation therapy that places a radioactive source directly in or near the tumor, is most commonly used intraocularly to treat melanoma of the eye.
In advanced stages of eye cancer, sometimes chemotherapy or immunotherapy will be used. Chemotherapy involves systemic cell destruction, while immunotherapy sensitizes the body to destroy invading cancer cells. For cases of metastatic eye cancer, systemic therapy may involve chemotherapy or targeted therapy to eliminate the cancer and increase survival. Some patients will need to undergo enucleation, which is the removal of the eye if the cancer is progressive or beyond the eye's salvage. This is likely to be emotionally difficult, but with prosthetics and rehabilitation, it is becoming easier for individuals to continue their lives after eye loss.
Several factors affect the prognosis of an eye cancer patient: the type of cancer, the extent of its spread, and the patient's health at the time of diagnosis. Thus early detection and treatment will ensure better outcomes, as eye cancer spreads rapidly if left untreated. Prognoses for intraocular melanoma are variable and improve with smaller tumor sizes at presentation due to better chances of treatment and survival. However, even in this case, when the disease has spread beyond the eye to other parts of the body, the prognosis is not as bright; chances of survival are generally poor.
Regular eye exams can help detect any type of eye cancer at an early stage in people at high risk. Individuals who have a family history of eye cancer, have certain genetic conditions, or are environmentally prone to developing melanoma should get regular eye exams. Protecting the eyes from harmful exposure to UV rays by wearing UV-protective sunglasses and not using tanning salons will also help reduce the risk of developing eye cancer.
Eye cancer is caused by several types of cancers arising from various parts of the eyes or surrounding structures such as the temporal or orbit. Cancers classified as eye cancer may be primary or originating from another region of the body, and such cancers spread to the eyes; therefore, they may be primary or secondary. Most eye cancers have subtle symptoms. Therefore, detection during the early period is essential for successful treatment. Various treatment options may be available depending on the type and stage of cancer. The options will include surgery, radiotherapy, chemotherapy, or any combination. They are rare cancers, but pose a significant public health issue due to their ability to metastasize and compromise vision. Certain preventive measures as well as regular check-ups at the eye clinic will substantially reduce the risk and improve the chances of early detection and successful treatment.
