What is ocular melanoma? Medical mystery shines light on rare eye cancer

Researchers are looking into what may be causing a rare eye cancer to strike groups of patients in two states. Ocular melanoma is an extremely rare form of cancer -- usually found in just six of every one million people. But as "CBS This Morning" reported Monday, it has been identified in 18 patients in Huntersville, North Carolina, and in a separate group of patients in Auburn, Alabama, including several friends who'd attended Auburn University together.

While the Alabama Department of Health says it would be "premature to determine that a cancer cluster exists in the area," researchers are studying the patients to try to figure out if there is a common source that might explain this unusual occurrence.

What is ocular melanoma?

Melanoma is a type of cancer that develops in cells that produce melanin, or the pigment that gives skin its color. While it's generally thought of as a skin cancer, eyes also have these melanin-producing cells, and when melanoma develops on them, it's called ocular melanoma.

Most of these cancers develop on the part of the eye that's not visible when looking in a mirror, often making it difficult to detect. In many cases, ocular melanoma will not cause early signs or symptoms.

According to the Mayo Clinic, if symptoms do occur, they can include:

• A growing dark spot on the iris
• A sensation of flashing lights
• A change in the shape of the pupil
• Poor or blurry vision in one eye
• Loss of peripheral vision
• Sensation of flashes and specks of dust in your vision (floaters)

If you experience any of these symptoms, make an appointment with your doctor.

What causes ocular melanoma?

It is currently unclear what causes ocular melanoma, though researchers know it occurs when errors develop in the DNA of healthy eye cells. These errors cause the cells to grow and multiply leading mutated cells to accumulate on the eye and form a melanoma.

There are several risk factors that can increase a person's chances of ocular melanoma, including having a light eye color, being Caucasian, getting older, having an inherited skin disorder, and exposure to ultraviolet (UV) light.

Complications of ocular melanoma

Ocular melanoma can lead to a number of complications, including glaucoma, or increasing pressure within the eye that can damage the optic nerve. Signs of glaucoma include eye pain, redness and blurry vision.

Ocular melanoma may also lead to vision changes and vision loss. Very advanced cases can cause complete vision loss.

There is also the possibility that the cancer will metastasize, or spread beyond the eye to distant parts of the body, including the liver, lungs, and bones. 

According to the Ocular Melanoma Foundation, 50 percent of ocular melanoma patients will develop metastases by 10 to 15 years after diagnosis.

Since cancer that has metastasized is often deadly, it is important to catch ocular melanoma early before it spreads. Treatments include radiation therapy or surgery to remove the tumor. In some cases, that may require surgery to remove the affected eye.

That was the difficult option faced by Juleigh Green, who was diagnosed with ocular melanoma at age 27.

Her doctor told her, "'There's a mass there, there's something there, I don't know what it is, but it looks like it could be, you know, a tumor,'" Green told "CBS This Morning." "It's like you had the breath knocked out of you, you know?"

Her college friend from Auburn University, Allison Allred, was 31 when she got the same diagnosis in 2001. "I was just seeing some mild flashes of light for, say, 7 to 10 days," Allred recalled. She, too, had to have the eye removed, but the cancer still spread to six other places in her body, including her brain.

Then their friend Ashley McCrary found black spots in her iris. It was the same rare cancer. McCrary started the Auburn Ocular Melanoma Facebook page, which has so far connected 36 people who say they attended Auburn University and have been diagnosed with ocular melanoma.

"We believe that when we're looking at what's going on in Huntersville, North Carolina, and what's going on here, there is something that potentially links us together," she said.