Shock value is hard to produce in the Internet age, but some attendees of the International Tattoo Festival in Caracas, Venezuela, gave it their best shot last week.

The four-day festival, organized to spread awareness of extreme body art, featured ghoulish face tattoos, extreme piercings, bifurcated tongues and Kala Kaiwi, the Hawaiian man who owns the world record for earlobe stretching.

But the festival’s most eye-popping body modification was almost certainly eyeball tattoos. You may not have realized that eyeball tattoos are a thing, but they are — and have been for some time.

The man usually credited with founding the Dark Willow-like trend is an American tattoo artist known as Luna Cobra, who refers to himself as a “pioneer in his field.”

Cobra’s original goal, he told the BBC, was to modify his eyes so they’d resemble the bright blue eyes of characters from the 1984 sci-fi film “Dune.”

The technique “involves injecting pigment directly into the eyeball so it rests under the eye’s thin top layer, or conjunctiva,” according to the BBC, and Cobra first tried it on several volunteers at a tattoo show in Canada.

“I’m aware of how insane that sounds,” he told the BBC, “but I’ve been doing this type of thing for my whole life, so I wasn’t coming from nowhere with this.”

The eye-coloring is permanent, which hasn’t stopped hundreds of people in countries all over the world from turning their eyes blue, green, red and black, he said.

“If you want to amuse yourself by decorating your eyeball, why not do it?” he said. “I do a lot of things that look like tie-dye or ‘cosmic space’. I think it brings a realm of fantasy into everyday life.”

Which brings us to a logical question: What does it feel like to have a needle stuck in your eyeball?

“It was mentally intense,” Kylie Garth told the BBC, noting that her turquoise-colored eyeballs have generated only positive attention. “It feels like somebody is poking at your eye, then it feels like strange pressure and then it feels you have a bit of sand in your eye, but there’s no pain.”

The American Optometric Association is not a fan of the practice, pointing out that getting eyeball tattoos can put people at risk of infection, inflammation and blindness.

“My advice is not to do it as there’s not enough benefit to even warrant considering that risk of potential pain and loss of vision,” Jeffrey Walline of the association’s Contact Lens and Cornea Council told the BBC.

Even Cobra, the originator of the practice, urges caution, telling young people to wait until they’re employed before tattooing their eyes, according to the BBC.

“I tell them you’re going to look frightening forever to the majority of people you encounter,” he said. “You might find people have trouble connecting with you or looking at you because they can’t follow your iris.”

The emerging trend, he told the BBC, has come as a shock.

“We had no idea anyone else would do it. And now everyone’s obsessed with it,” he said. “We often felt like we released a beast into the world and now all these people will be damaged.”

He added: “It’s a shame because I think it’s something really beautiful, but it’s taken an odd course.”