Two-year-old Violet Pietrok was born with an extremely rare condition called Tessier facial cleft, leaving the bones in her face so spread apart that her nose lacked cartilage and her eyes didn’t have normal vision.

Because the defect is so rare, not many doctors have experience with repairing it — but one plastic surgeon located in Boston, Dr. John Meara, seemed to offer the Pietroks some hope: He had performed four operations on children with similar defects in the past several years. Meara and his team planned to use 3D printing to recreate a mold of Violet’s skull, then practice operating on it, chiseling out areas that had problems and bringing the two parts of her skull closer together to fill the gap between her eyes.

“Normally you can’t see certain aspects of the skeleton with skin covering and muscle covering the area,” Meara, who is the plastic-surgeon-in-chief at Boston Children’s Hospital, says in a New York Times video. “3D printing allows you to see areas and actually dissimilate surgery in ways that’s never been possible before.”

Doctors would cut into Violet’s facial bone, and using the practice 3D-printed mold as a guide, complete the complicated procedure that involved moving her eyes together and pressing her bones into a more normal position.

“The printer lays this resin down, moving up through the skull, thousands and thousands and thousands of layers with acrylic being added in very specific spots,” Meara says in the video. “So when I’m looking at a complex cranio-facial condition like this, I’m able to turn this over and look at various areas where I might need to make special cuts in the bone.”