Driving home after having some pigment spots removed from his skin by laser, Gregg Homer wondered what would happen if you used a similar laser on the eyes.

An inventor who had a Ph.D in biology, Homer did a little research and quickly realized the potential of the idea: a study in the 1980’s had shown that underneath every brown eye is a blue eye. And that brown layer, Homer discovered, appeared to be superficial enough that it could, theoretically, be removed.

“I went back to my dermatologist and said, I’ve got a question for you,” Homer told Discovery News. “What would happen if you used this on an iris?”

The dermatologist eventually joined his board of investigators, and now, almost 20 years later, the surgery is going through human testing in Costa Rica via Homer’s company called Stroma.

The original idea, that the frequency of the green laser is such that it passes straight through the cornea and is only absorbed by dark color, makes it “incredibly safe and incredibly differentiating,” Homer said.

The change isn’t immediate; the laser is set at a low energy so that the blue eye is revealed over a couple of weeks.

While there have been no adverse effects in the 37 people who have had one eye treated in trials outside of the U.S., Homer said, it’s too early to say for certain what long-term effects the procedure could have. Ophthalmologists say the primary health concern, at least theoretically, is glaucoma.

“Maybe you don’t see it immediately, but 10 years down the road it could be a public health problem,” Dr. Ivan Schwab, an ophthalmologist and clinical spokesperson for the American Academy of Ophthalmology and professor of ophthalmology at the University of California, Davis, told Discovery News.

“I wouldn’t completely dismiss the procedure; I’m not going to tell you it won’t work, but my biggest concern is long-term problems,” he added.

Other issues could include infections and improper use of the equipment by ophthalmologists who perform it, similar to issues with LASIK, Schwab said.

Still, “it’s a very attractive idea if you think about it, to turn brown eyes blue,” Schwab said.

So far, none of the patients in the trials have experienced an increase in pressure which precedes glaucoma, Homer said; in fact, most have shown a decrease. Because the surgery removes pigment on the front of the iris, not the back, which is where fragments of pigment can become trapped and lead to a blockage that can cause glaucoma, and because the laser breaks the pigments into extremely fine particles, the risk for glaucoma is low, he said.

Picture the cells like clear empty bags with granules of pigment, Homer said.

“If you hit the pigment cell it heats up the pigment and eventually it bursts the cell, and the pigment granules are released into the fluid in the front chamber of the eye,” he said.

Instead of exploding it on impact, the researchers looked for a “sweet spot” where the pigment could be agitated enough that the body would take over and do the rest of the work on its own.

Homer said he won’t release the procedure to the public until he deems it safe enough for his 20-year-old, brown-eyed daughter.

“She’s been obsessed with it,” he said. “And as we treat more people, we’re getting closer and closer.”

Homer doesn’t expect the procedure to be available in the U.S. anytime soon.

Getting the treatment in the U.S. is a ways down the line, and is expected to cost about $5,000. But Homer said he expects the procedure to be available in other countries much more quickly.

For the record, Homer himself has blue eyes, as does country singer Crystal Gayle, who recorded the song “Don’t It Make My Brown Eyes Blue” in 1977.