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Johns Hopkins Pediatric

3-D Modeling: Improving Results of Orbital Surgery

Michael Grant, MD, PhDSightline Special Edition
Annual Report 2014

Michael Grant, M.D., Ph.D., is a reconstructive eye surgeon who sees surgery differently than most other doctors. It’s not that he views the practice of surgery differently. It’s that Michael Grant literally sees things differently than most.  

“We’re using advanced three-dimensional imaging and pre-operative computer assisted planning to help us make surgeries safer, more predictable and, ultimately, more successful for patients,” says Grant, who directs the Wilmer Eye Institute’s Ocular and Orbital Trauma Center.

Grant is among a handful of surgeons around the world using today’s remarkable computer technology to craft exact-scale patient models to improve surgical outcomes in orbital surgery.

“The eye is an incredibly complex, confined environment where you have the delicate eye, of course, and nerves—two of which are attached to the eye—muscle and bone, all in very close proximity. It’s a technically demanding environment,” he says. “Being able to see things in three dimensions is a great advantage.” 

Whether he is correcting general reconstructive problems, congenital malformations or traumatic injuries, Grant’s orbital reconstruction efforts often involve manipulating the bones of the eye socket—structures that are hidden from view. The traditional practice has been to handle what is, by every measure, a three-dimensional problem in just two dimensions, by using flat images for planning.

While 2-D imaging certainly helps doctors peer through the soft tissues to understand and plan bone reconstruction, this approach is limiting. Like playing golf with one eye closed, the surgeons are handicapped from the start.

“Not a lot of sophisticated planning was possible, but we can now operate within a millimeter of accuracy and assess our success while still in the operating room,” Grant says.

He begins by taking a series of preoperative CT scans of the patient and feeding the data into sophisticated computer algorithms that produce an exact-scale model of the patient. In essence, he is creating a virtual patient.

Sometimes those models exist on a computer screen. After planning his surgery in his office, he downloads the imagery to a USB memory stick, takes it into the operating room and, using advanced technologies developed by a company in Germany, projects his plans directly onto the face of the patient. 

Like a surgical GPS, these maps guide his every incision in real time. Then, before he wraps up, Grant can compare his plan against the results, all while still in the operating room. If necessary, he can adapt on the spot, reducing the need for follow-up surgeries.

In other instances, Grant prints out life-size, exact-scale plastic models using a 3-D printer. By surgically manipulating the models, he can get a much better feel for what he needs to do in the operating room.

In one example, Grant explains how he used plastic, 3-D printed models as his surgical patient, cutting and manipulating the plastic “bones” of the virtual patient’s left eye socket to model how he wanted to reconstruct that patient’s damaged right eye socket. In the operating room, the surgery then became like solving a jigsaw puzzle, with Grant cutting and shaping the pieces of real bone to match those he created in his models.

“This is definitely the next generation of surgical planning and another example of the Wilmer Eye Institute’s leadership,” Grant says. “Wilmer has always been at the cutting edge, always looking for ways to use technology to take on the most difficult clinical problems in new ways.”

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