Definition

Melanoma is a malignant tumor originating in cells that produce melanin, the pigment responsible for the coloration of skin, hair, and eyes. Eye pigment is located in the iris, the colored ring encircling the pupil.

Most eye melanomas develop in parts of the eye not visible when looking in the mirror, making them difficult to detect. Eye melanoma typically does not present early signs or symptoms. Despite being the most common eye cancer in adults, eye melanoma is rare.

Eye melanoma predominantly arises in the uvea's cells, the middle layer of the eye, which comprises three parts, each susceptible to melanoma:

• The iris, the colored part at the front of the eye
• The choroid, the blood vessel and connective tissue layer at the back of the uvea
• The ciliary body, situated in front of the uvea, which secretes aqueous humor into the eye

In rare instances, eye melanoma can also occur in the conjunctiva, the outermost layer at the front of the eye, the cavity surrounding the eyeball, and on the eyelids.

Causes

The precise cause of eye melanoma is not well understood. Research indicates that development errors of DNA in eye cells lead to uncontrolled cell growth and multiplication, allowing mutated cells to survive when they should have died. These accumulating mutated cells form eye melanoma.

Risk Factor 

Risk factors for eye melanoma include:

• Light eye color. Individuals with blue or green eyes are at a higher risk of eye melanoma.
• Caucasian race. Caucasians are more susceptible to eye melanoma compared to other races.
• Age. The risk of eye melanoma increases with age.
• Inherited skin disorders. Conditions like dysplastic nevus syndrome, which causes abnormal moles, can increase the risk of melanoma in both the skin and eyes.

Additionally, those with abnormal skin pigmentation around the eyes and increased uveal pigmentation (ocular melanocytosis) are at higher risk.

• UV rays exposure. There is some evidence suggesting that UV rays exposure may elevate the risk of eye melanoma.
• Genetic mutations. Certain inherited genetic mutations can increase the likelihood of developing eye melanoma.

Symptoms

Eye melanoma may not exhibit symptoms early on. As the disease progresses, symptoms may include:

• Sensation of flashes or specks of dust in vision (floaters)
• Black spots on the iris
• Changes in the shape of the pupil
• Blurred or poor vision in one eye
• Loss of vision on the side of the eye

Diagnosis

To diagnose eye melanoma, the following tests may be recommended:

• Eye examination. The doctor examines the outer part of the eye for enlarged blood vessels that could indicate a potential tumor and uses a tool to inspect the interior part of the eye.
• Ocular ultrasound. 
• Angiogram. A dye is injected into an arm blood vessel, traveling to the eye's blood vessels, detected by a special camera, to identify abnormal vessels indicative of a tumor.
• Optical coherence tomography. Produces images of the uveal tract and retina.
• Biopsy. In some cases, a tissue sample from the tumor is tested in a lab for melanoma cells. Although not always necessary for diagnosis, it provides detailed information about the tumor and its spread.

The ophthalmologist may refer the patient to other specialists for more tests to determine whether the melanoma has spread or metastasized. These tests may need to be repeated several times. Additional tests to check for metastasis may include:

• Liver function tests
• Chest X-ray
• CT scan
• MRI
• Abdominal ultrasound
• Positron Emission Tomography (PET) scan

Management

Treatment options for eye melanoma depend on the location, size of the melanoma, the patient's overall health, and patient preferences. Treatment for some small eye melanomas may not affect vision. However, treatment for large eye melanomas may cause vision loss.

Several choices of eye melanoma therapy include:

• Observation for small eye melanoma

A small eye melanoma may not require immediate treatment. If the melanoma is not growing, your doctor may choose to observe or watch for signs and symptoms. If the melanoma grows or causes complications, you may choose to get treatment right away.

• Radiation therapy

Radiation therapy uses high-energy radiation to kill cancer cells and is usually used for small to medium-sized eye melanomas.

• Laser treatment

This treatment is an option in certain situations. One type of laser treatment, called thermotherapy, uses an infrared laser and is sometimes combined with radiation therapy.

• Photodynamic therapy

Photodynamic therapy combines drugs with a specific wavelength of light. The drugs make cancer cells susceptible to light, damaging the blood vessels and cells that make up the eye melanoma. This therapy is used for smaller tumors as it is not effective for larger tumors.

• Cryotherapy

Cryotherapy, or extreme cold therapy, can be used to destroy some small eye melanomas but is not commonly used.

Surgery to treat eye melanomas may involve removing part or all of the eye. The specific procedure depends on the size and location of the melanoma. The surgery options include: 

• Surgery to remove the melanoma and a small amount of healthy tissue

This may be an option for treating small melanomas.

• Surgery to remove the entire eye (enucleation)

Enucleation is often used for large eye tumors or if the tumor is causing pain. After removing the eye with melanoma, an implant is used to replace it in the eye socket. The muscles controlling eye movement are attached to the implant, allowing it to move. After recovery, an artificial eye (prosthesis) will be fitted.

Complications

Complications of eye melanoma include:

• Increased intraocular pressure (glaucoma). Large melanomas can cause glaucoma, leading to eye pain, redness, and blurred vision.
• Vision loss. Large melanomas can result in vision loss and complications like retinal detachment. Even small melanomas can cause blindness if they affect critical areas of the eyes.
• Metastasis. Eye melanoma can spread to other organs, such as the liver, lungs, and bones.

Prevention

The exact cause of eye melanoma remains unknown, making effective prevention difficult. However, limiting sun exposure can reduce the risk of skin melanoma, potentially lowering eye melanoma risk as well. Preventive measures include using sunscreen or wearing a hat when outdoors.

The American Cancer Society also recommends glasses with 99%-100% UVA and UVB protection to safeguard the eyes and surrounding skin.

When to See a Doctor?

Consult your doctor if you have any worrying signs or symptoms, such as sudden changes in your vision, which are considered emergencies and require immediate treatment.

If you have undergone cancer treatment that has resulted in total vision loss in one eye, you can still perform most activities as before, but it may take several months to adjust.

Having only one eye can affect your ability to judge distances and notice things around you. Consider consulting an occupational therapist to help you adjust to your new vision.

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