Ocular Melanoma: Symptoms & Treatment

Melanoma is a form of cancer that originates within melanocytes, which are cells in the eyes and skin that produce and store the pigment, also known as melanin. Ocular melanoma specifically affects the eye. 

The exact causes of ocular melanoma are not fully understood, but it is widely known that exposure to ultraviolet (UV) radiation increases the risk for developing this type of cancer. 

What Is Ocular Melanoma?

Ocular melanoma specifically affects the eye. It is a very rare form of cancer, with an incidence of 1 in 5 million. 

Ocular melanoma differs from many other cancers, as it is a primary form of cancer that begins specifically in melanocytes in the eyes and does not spread to other areas of the body. Melanocytes are cells that store melanin, which is a pigment that provides color to the skin. 

Though rare, instances of this form of cancer are increasing throughout the world, particularly in women and individuals under 40. Understanding the risk factors and causes is essential for prevention and early detection. 

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Causes

The causes of ocular melanoma are not entirely understood. 

Current understanding of the causes of ocular melanoma is limited to knowledge that the mutations develop in the DNA of healthy melanocytes in the eyes. These DNA errors signal cells to grow at an unhealthy rate, and mutated cells continue living instead of dying as normal. 

Mutated cells accumulate, forming the ocular melanoma. Why this occurs is not widely understood. However, researchers have found a significant link between ocular melanoma and UV radiation exposure. More prolonged exposure and exposure to stronger levels of UV radiation are significantly related to ocular melanoma. 

Symptoms of Ocular Melanoma

Melanomas can develop on any part of the epidermis, while ocular melanoma specifically occurs in the eye. While regular melanomas are most likely to develop in areas that have more exposure to the sun, such as the nose, arms, and legs, ocular melanomas are restricted to the melanocytes in the layer underneath the white part of the eye. 

Other forms of melanoma can also occur in areas that do not have significant exposure to the sun, such as the bottoms of the feet and in the beds of your fingernails. Likewise, melanomas in the eye are difficult to detect and may not always be linked with significant exposure to the sun.

Three types of hidden ocular melanomas are as follows:

1. Choroidal ocular melanoma: These are most commonly present in the layer beneath the white of the eye, or the uvea, and the retina. The uvea is located below the sclera, or the white part of the eye. The retina is the light-sensitive structure located in the back of the eye that sends visual information to the visual cortex in the brain.
   
   You may detect this type of melanoma by noticing changes in your vision.
   
2. Iris ocular melanoma: This type of ocular melanoma is the most common primary cancer of the iris and accounts for 5 percent of all uveal melanomas as well. Individuals in their 50s face the highest incidence of this type of ocular melanoma.
   
3. Uveal ocular melanoma: This type of ocular melanoma develops in the melanocytes within the uvea or uveal tract in the eye. The uvea is the middle layer of the eyewall. It consists of the ciliary body, choroid, and iris. 

Risk Factors 

Some factors can make you more susceptible to developing melanoma. You are at an increased risk if any of the following apply to you:

• Lighter eye color
• Caucasian descent
• A familial history of melanoma
• Older age
• A history of multiple or severe sunburns
• Having an inherited skin disorder
• Prolonged exposure to UV light and/or exposure to more intense UV radiation
• Living close to the equator
• Living at a high elevation
• Numerous and/or atypical moles
• A weak or compromised immune system
• Certain genetic mutations

Diagnosis of Ocular Melanoma

Ocular melanomas are diagnosed through several tests. Here are some of the tests used:

Ultrasonography

This technique involves the use of ultrasound pulse echoes to distinguish objects with different density in the body.

Fluorescein Angiography

This involves the use of a specialized camera to take pictures of blood flow in the back of the eye and retina.

Enhanced Depth Imaging Optical Coherence Tomography

Also known as EDI OCT, this technique involves the use of SD-OCT equipment that is positioned close to the eye so that a stable and highly sensitive image of deep layers of tissue are achieved.

Fine-Needle Aspiration Biopsy

This involves the insertion of a fine needle into the eye to take a sample of a suspected melanoma.

Treatment of Ocular Melanoma

Treatment depends on the result of the diagnosis and the type of ocular melanoma that is diagnosed. The following are common treatments of ocular melanomas:

Resection Surgery

This is the surgical removal of a tumor and a small amount of healthy tissue.

Enucleation

This is surgery to remove the eye and a piece of the optic nerve.

Exenteration 

This is surgery to remove the eyelid, eye, muscles, nerves, and fibers from the eye socket.

Radiation Therapy

This involves the use of high-energy x-rays and/or other types of radiation to target and kill cancer cells.

Photocoagulation

This uses laser light to destroy blood vessels that supply nutrients to a tumor.

Thermotherapy

This uses laser-induced heat to destroy cancerous cells.

Complications of Ocular Melanoma

Large ocular melanomas can cause vision loss and complications like detachment of the retina. Small ocular melanomas may cause some vision loss or impairment. Additional complications include cataractogenesis and glaucoma.

Prevention

The best way to prevent ocular melanomas is to limit exposure to intense sunlight and radiation. This can be done by wearing protective eyewear that has 99 to 100 percent UVA and UVB protection, wide-brimmed hats, and protective clothing. You can also use umbrellas when outdoors to prevent sun exposure. 

Avoid being in direct sunlight during the hottest times of day.

Prognosis

The five-year survival rate for ocular melanoma is approximately 82 percent. When this cancer does not spread outside of the eye, the rate increases to 85 percent. When cancerous cells spread to surrounding tissues, the five-year survival rate is 71 percent.

Prompt diagnosis and treatment provide the best long-term prognosis for ocular melanoma.

References

1. Ocular Melanoma. (May 2022). National Library of Medicine.

2. Ocular Melanoma. (2018). National Organization for Rare Disorders. 

3. Risk Factors for Eye Cancer. (November 2018). American Cancer Society. 

4. What Is Ocular Melanoma? (November 2022). American Academy of Ophthalmology.

5. Uveal Melanoma: Estimating Prognosis. (February 2015). Indian Journal of Ophthalmology.

6. Future Perspectives of Uveal Melanoma Blood Based Biomarkers. (February 2022). British Journal of Cancer.