Overview
Eye cancer can refer to any cancer that starts in the eye. The most common type of eye cancer is melanoma and is usually found in adults. To know more about Retinoblastoma which is common among children, please click here. But there are other types of cancer that affect different kinds of cells in the eye.
Eye cancers can happen in 3 regions of the eyes:
- The eyeball (globe) that is mostly filled with a jelly-like material called vitreous humor and has 3 main layers (the sclera, the uvea, and the retina)
- The orbit (the tissues surrounding the eyeball)
- The adnexal (accessory) structures such as the eyelids and tear glands.
Cancers that affect the eye itself are called intraocular (within the eye) cancers. The ones that start in the eye are called primary intraculoar cancers. Secondary intraocular cancers are the ones that happen elsewhere and spread to the eye.
In adults, the most common primary intraocular cancers are:
- Melanoma
- Non-Hodgkin lymphoma
In children, the most common primary intraocular cancers are:
- Retinoblastoma: A cancer that starts in cells in the retina (the light-sensing cells in the back of the eye)
- Medulloepithelioma: This is the second most common but is still extremely rare.)
Most external tumours are relatively benign and slow growing and can be treated by superficial excision. Internal tumours involving the retina and choroid are more serious and often call for radiation and other therapy in addition to surgery. They include intraocular melanoma in adults and retinoblastoma in children, both of which can metastasise to other organs. Many of the more common cancers, such as breast and lung cancer, can spread to the eyes.
Melanoma:
Intraocular Melanoma: Intraocular melanoma is the most common type of cancer that develops within the eyeball in adults but it is still fairly rare. Melanomas that start in the skin are much more common. Melanomas develop from pigment-making cells called melanocytes. When melanoma develops in the eye, it is usually in the uvea (uveal melanomas) and rarely in the conjunctiva (conjuctival melanomas):
- Uveal Melanoma: The uvea is the middle layer of the eyeball. It has 3 main parts:
- The iris is the colored part of the eye (most often blue or brown). It surrounds the pupil, the small opening where light enters the eyeball.
- The choroid is a thin, pigmented layer lining the eyeball that nourishes the retina and the front of the eye with blood.
- 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.
- Almost 9 out of 10 intraocular melanomas develop in the choroid or ciliary body. Choroid cells make the same kind of pigment as melanocytes in the skin, so it’s not surprising that these cells sometimes form melanomas.
- Most of the other intraocular melanomas start in the iris. These are the easiest to see because they often start in a dark spot on the iris that has been present for many years and then begins to grow. These melanomas usually are slow growing, and they rarely spread to other parts of the body. For these reasons, people with iris melanomas generally have a good prognosis (outlook).
- Uveal melanomas can spread through the blood and commonly spread to the liver.
- Conjunctival Melanoma: The conjunctiva is a thin clear covering over the sclera. (The sclera is the tough, white covering over most of the outside of the eyeball. In the front of the eye it is continuous with the cornea, which is clear to let light through.) These melanomas are extremely rare. They tend to be more aggressive and grow into nearby structures. Because they can spread through the blood and the lymph system, they can also spread to distant organs like the lungs, liver, or brain where the cancer can become life-threatening.
The other cancers that can affect the eye are orbital and adnexal cancers. The orbit consists of the tissues surrounding the eyeball. These include muscles that move the eyeball in different directions and the nerves attached to the eye. Cancers of these tissues are called orbital cancers.
Adnexal (accessory) structures include the eyelids and tear glands. Cancers that develop in these tissues are called adnexal cancers. Cancers of the orbit and adnexa develop from tissues such as muscle, nerve, and skin around the eyeball and are like cancers in other parts of the body.
Symptoms
Eye melanoma does not have symptoms unless the cancer grows in certain parts of the eye or has advanced. Other, less serious conditions can also cause many of these symptoms. For example, floaters can be a normal part of the aging process.
Signs and symptoms of eye melanomas can include:
- Blurry vision or sudden loss of vision
- Floaters (spots or squiggles drifting in the field of vision) or flashes of light
- Visual field loss (losing part of your field of sight)
- A growing dark spot on the iris
- Change in the size or shape of the pupil
- Change in position of the eyeball within its socket
- Bulging of the eye
- Change in the way the eye moves within the socket
- Pain is rare unless the tumour has grown extensively outside the eye
Causes
The exact cause of most eye cancers is not known. But scientists have found that the disease is linked with some other conditions, which are described in Risk Factors for Eye Cancer. A great deal of research is being done to learn more about the causes.
Following are some of the causes as well as risk factors that can cause eye cancer:
- Eye colour: It is considered that a person with light coloured eyes like, blue, green or grey eyes, is more likely to develop melanoma of the eye as compared to people with brown eyes
- Skin colour: A light skin tone is also considered to be one of the causes of the development of eye cancer
- Moles: Moles also feature in the risk factor list. A person with moles is at a greater risk of skin and eye melanoma
- Sunlight: Long and continuous exposure to the sun can increase the risk of eye cancer in a person
- UV radiation
- Weakened immune system: People are at a higher risk level if they have been infected by viruses like AIDS or human papilloma virus or autoimmune diseases like rheumatoid arthritis
- Drugs that suppress the immune system
Diagnosis
Examination of the eye by an ophthalmologist (a medical doctor specializing in eye diseases) is often the most important first step in diagnosing melanoma of the eye. While checking the eye for vision and eye movement, the doctor also enquires about the symptoms. The doctor will also look for enlarged blood vessels on the outside of the eye, which can be a sign of a tumour inside the eye.
The ophthalmologist may also use special instruments to get a good look inside the eye for a tumour or other abnormality. Drops may be applied in the eye to dilate the pupil before the doctor uses these instruments:
- An ophthalmoscope: A hand-held instrument consisting of a light and a small magnifying lens.
- Indirect Ophthalmoscope: It sits still on a platform and provides stronger magnification to get a more detailed view.
- A gonioscopy lens: It is a specially mirrored lens that is placed on the cornea (the outer part of the eye) after it is numbed. It can be used to look for tumour growth into areas of the eye that would otherwise be hard to see.
Apart from the above tests, other tests or a combination thereof may be recommended such as:
- Imaging studies: Ultrasound scans, fluorescein angiography, CT scans, X-Ray, and MRI scans are used to diagnose the cancers. They show the size, location and shape of the tumours and also show any enlarged or affected lymph nodes around the eyes. These lymph nodes may carry cancer cells
- Biopsy: Usually a fine needle is used to aspirate some vitreous fluid from within the eye. The sample is examined under the microscope for lymphoma cancer cells
- Lumbar puncture or spinal tap: Since eye lymphomas may be an extension of Central Nervous System lymphomas, a spinal tap to examine the Cerebrospinal fluid may be needed. The CSF bathes the brain and the spine and thus may offer clues to affliction of the spine or brain with lymphoma
- Bone marrow examination may be done to exclude spread or other locations of the lymphoma
Treatment
Surgery:
The type of surgery depends on the location and size of the tumour, how far the tumour has spread, and the person’s overall health. All of these operations are done under general anaesthesia. The operations used to treat people with eye melanoma include:
- Iridectomy: Removal of part of the iris. This might be an option for very small iris melanomas.
- Iridotrabeculectomy: Removal of part of the iris, plus a small piece of the outer part of the eyeball. This might also be an option for small iris melanomas.
- Iridocyclectomy: Removal of a portion of the iris and the ciliary body. This operation is also used for small iris melanomas.
- Trans-scleral resection: Surgically removing just a melanoma of the ciliary body or choroid.
- Enucleation: Removal of the entire eyeball. This is used for larger melanomas, but it may also be done for some smaller melanomas if vision in the eye has already been lost or if other treatment options would destroy useful vision in the eye, anyway. During the same operation, an orbital implant is usually put in to take the place of the eyeball. The implant is made out of silicone or hydroxyapatite (a substance similar to bone). It is attached to the muscles that moved the eye, so it should move the same way as the original eye would have.
- Orbital exenteration: Removal of the eyeball and some surrounding structures such as parts of the eyelid and muscles, nerves, and other tissues inside the eye socket. This surgery is not common, but it might sometimes be used for melanomas that have metastasized.
Radiation Therapy:
Radiation therapy uses high-energy x-rays to kill cancer cells. It is a common treatment for eye melanoma. Radiation therapy can often save some vision in the eye.
- Brachytherapy: In this form of radiation therapy, the doctor places small seeds of radioactive material directly into or very close to the cancer. The radiation from the seeds travels a very short distance, so most of it will be focused only on the tumour.
- External beam radiation therapy: In this approach, radiation from a source outside the body is focused on the cancer. For eye melanomas, the use of this type of radiation therapy is generally limited to newer methods that focus narrow beams of radiation on the tumour, such as proton beam radiation therapy or stereotactic radiosurgery
Laser Therapy for Eye Cancer:
Laser therapy is sometimes used to treat eye melanoma, especially when surgery or radiation are not possible. Types of laser therapy used to treat eye cancer are:
- Transpupillary Thermotherapy: It uses infrared light to heat and kill the tumor.
- Laser Photocoagulation: This treatment uses highly focused, high-energy light beams to burn tissue.
Chemotherapy:
Melanoma usually does not respond well to standard chemo drugs. Chemo is used only when the cancer has become widespread. If chemo is used, the treatment is generally the same as for melanoma of the skin.
