Choroidal melanoma is a rare cancer that forms in the layer of blood vessels beneath the retina at the back of the eye. It is the most common primary eye cancer in adults, though it still affects only about 5 to 6 people per million each year. Symptoms can include blurred vision, flashes of light, a growing dark spot on the iris, or no symptoms at all in early stages. Treatment depends on tumor size and location, with options ranging from radiation therapy to surgical removal of the eye in advanced cases.
What Is Choroidal Melanoma?
Choroidal melanoma starts in the choroid, a thin layer of tissue packed with blood vessels that sits between the retina and the white outer coat of the eye called the sclera. The choroid supplies oxygen and nutrients to the retina, which is the light-sensitive tissue that sends visual signals to the brain.
When melanocytes — the pigment-producing cells in this layer — grow out of control, they form a tumor. Most choroidal melanomas are pigmented, meaning they appear brown or dark. Some are amelanotic, meaning they lack pigment and appear lighter, which can make them harder to spot during an eye exam.
This cancer is distinct from skin melanoma. It behaves differently, spreads differently, and requires different treatment. It is also unrelated to the much more common benign freckles or nevi that many people have inside their eyes.
What Are the Symptoms of Choroidal Melanoma?
Many people with choroidal melanoma have no symptoms at all when the tumor is first found. Often it is detected during a routine eye exam when an ophthalmologist looks at the back of the eye with a special lens.
When symptoms do appear, they depend on where the tumor is and how large it has grown. Common symptoms include:
- Blurred or distorted vision in one eye
- Flashes of light, known as photopsia
- A dark spot that grows on the colored part of the eye
- A feeling of pressure or pain inside the eye
- Loss of peripheral vision
- A change in the shape of the pupil
Because these symptoms can also come from far more common conditions like retinal detachment, migraines, or floaters, they do not automatically mean cancer. But any new or changing visual symptom should be evaluated by an eye care professional promptly.
How Is Choroidal Melanoma Diagnosed?
An ophthalmologist typically diagnoses choroidal melanoma through a dilated eye exam. The pupil is widened with drops so the doctor can see the back of the eye clearly. The tumor often has a distinct appearance — a dome-shaped or mushroom-shaped growth beneath the retina.
Ultrasound is the most important imaging test. It uses sound waves to measure the tumor’s thickness and width, and it can show internal characteristics that help confirm the diagnosis. Optical coherence tomography, or OCT, provides cross-sectional images of the retina and can show fluid or changes in the layers above the tumor.
In some cases, a doctor may order fluorescein angiography, which uses a dye injected into the arm to photograph blood flow in the eye. This test helps distinguish melanoma from other conditions that look similar, such as a benign nevus or a metastatic tumor from another cancer.
A biopsy is rarely needed. In most cases, imaging findings are clear enough to make the diagnosis without taking a tissue sample. Biopsy is reserved for unusual cases where imaging cannot tell the difference between melanoma and another lesion.
What Are the Treatment Options for Choroidal Melanoma?
Treatment has changed dramatically over the past few decades. In the past, removing the eye — a procedure called enucleation — was the standard approach for nearly all choroidal melanomas. Today, eye-sparing treatments are available for most tumors, and enucleation is reserved for very large tumors or eyes with no useful vision.
Radiation therapy is the most common treatment. There are two main types:
- Plaque brachytherapy — a small radioactive disc is sewn onto the wall of the eye over the tumor. It stays in place for several days and is then removed. This delivers a high dose of radiation directly to the tumor while limiting exposure to healthy tissue.
- Proton beam therapy — a focused beam of proton particles is aimed at the tumor from outside the eye. This is typically done over several sessions and offers precise targeting.
Both forms of radiation are effective at controlling the tumor in most cases. Research consistently shows that radiation and enucleation offer similar survival rates, which is why eye-sparing treatment is now preferred whenever possible.
Laser therapy can be used for small tumors. Photocoagulation uses a laser to destroy blood vessels feeding the tumor. Transpupillary thermotherapy, or TTT, uses heat to kill tumor cells. These are less commonly used as primary treatment today but may play a role for small, carefully selected tumors.
Surgical removal of the tumor, known as local resection, is possible in rare cases. This involves removing the tumor and a margin of healthy tissue while leaving the eye intact. It is technically demanding and carries risks, so it is only offered at specialized centers for certain tumors.
Enucleation remains necessary for some patients. It is recommended when a tumor is too large for radiation, when the eye is already blind and painful, or when the tumor extends outside the eye. After removal, the eye socket is fitted with a prosthetic that looks natural and moves with the remaining eye muscles.
What Is the Prognosis for Choroidal Melanoma?
Outcomes depend heavily on tumor size and whether the cancer has spread beyond the eye at the time of diagnosis. The most important factor is the presence of metastasis, which most often spreads to the liver.
Small tumors that are treated early have an excellent prognosis. Most patients with small melanomas do not develop metastatic disease. Larger tumors carry a higher risk of spreading, even years after the eye is successfully treated.
Choroidal melanoma can metastasize late. Some patients develop liver metastases 10 to 15 years after their initial treatment. This is why long-term follow-up is essential, including regular blood tests and liver imaging in some cases.
Genetic testing of the tumor, when a biopsy is performed, can provide additional information about the risk of metastasis. Tumors with certain genetic mutations, such as BAP1 loss, carry a higher risk of spreading. Tumors with other mutations, such as SF3B1 or EIF1AX, tend to behave less aggressively.
Can Choroidal Melanoma Be Prevented?
There is no known way to prevent choroidal melanoma. Unlike skin melanoma, it is not clearly linked to ultraviolet light exposure. The inside of the eye is shielded from UV radiation, and studies have not found a consistent connection between sun exposure and this type of cancer.
Certain risk factors are well established. People with fair skin and light-colored eyes are at higher risk. So are people with a condition called ocular melanocytosis, which causes a slate-gray discoloration of the white of the eye. People with a family history of uveal melanoma are also at increased risk, though this is rare.
The best protection is early detection. Regular dilated eye exams can catch tumors when they are small and more easily treated. There are no screening guidelines for the general public, but people with known risk factors should discuss their eye exam schedule with their doctor.
What Happens After Treatment?
Follow-up care after treatment is lifelong. The treated eye needs regular monitoring to check for tumor recurrence and to manage radiation side effects. The unaffected eye also needs routine exams because people who have had choroidal melanoma in one eye have a slightly higher risk of developing it in the other eye.
Radiation can cause side effects months or years after treatment. Common issues include radiation retinopathy, which damages the retina’s blood vessels, cataracts, glaucoma, and dry eye. These complications can reduce vision even when the tumor itself is controlled.
Vision outcomes vary widely. Some patients retain good vision after treatment, especially if the tumor is small and far from the center of vision. Others experience significant vision loss, particularly if the tumor is located near the macula, the part of the retina responsible for sharp central vision.
Regular systemic surveillance is also part of follow-up. Because the liver is the most common site of metastasis, many specialists recommend liver function blood tests and liver ultrasound every 6 to 12 months. The evidence for this surveillance improving survival is not firmly established, but it remains common clinical practice.
Frequently Asked Questions
Is choroidal melanoma the same as skin melanoma?
No, they are different diseases with different behavior and treatment approaches. Choroidal melanoma arises from pigment cells inside the eye, while skin melanoma arises from pigment cells in the skin.
Can choroidal melanoma be cured?
Yes, when the tumor is confined to the eye, treatment can control it in most cases. The main risk is metastasis, which can occur years later even after successful treatment of the eye itself.
How fast does choroidal melanoma grow?
Growth rates vary, but most choroidal melanomas grow slowly over months to years. This is why small tumors are sometimes monitored with serial ultrasounds to document growth before deciding on treatment.
Will I lose my eye if I have choroidal melanoma?
Not necessarily. Most patients today are treated with radiation that preserves the eye. Enucleation is only needed for very large tumors or eyes that are already blind and painful.
