Authorities were stunned to find that two prison inmates had undergone a painful and dangerous self-made tattoo procedure to permanently ink the whites of their eyes.

“It’s like the final frontier, nobody’s got it done,” Paul Inman told MSNBC in an interview. He tattooed his eyes dark blue to compliment his light blue eyes, and he’s currently serving 73 years on conspiracy to commit murder charges, arson and assault. “I bet you there’s no one in the world who has the same color of eyes as I do,” he added.

Inman and his cell mate David Boltjes–who tattooed the whites of his eyes blood red–is currently serving four years for credit card fraud, would not reveal how they were able to create the ink or the tattoo. “You don’t use a conventional tattoo gun or homemade tattoo gun,” said Boltjes. “Cause there’s a layer, you have to get in between the layer. You can use a hypodermic needle, but I’m not saying that’s what we used,” he added. “It’s painful, it’s like someone is taking hot ice picks and stabbing the back of your eyes.”

Both inmates will face disciplinary action for tattooing their eyes.