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EW NEWS & OPINION November 2017 27 University of Leuven, in order to develop such protocols. "We have been able to print with recombinant human collagen type III, and we have been able to show that we can print up to about 100 μm so these are still very thin, but they are up to 280 layers of col- lagen," she said. When they print, they are able to control the orientation of the collagen fibers, she added. Once the team has proof of principle, they will build on this further. The goal for now is to move to full thickness and develop corneas that are up to 400–450 μm thick for transplanta- tion in animals. "Eventually we'll get to humans, but there's still quite a long way to go," Dr. Zakaria said. Next steps Animal testing is expected to take place early next year, and they will look to determine whether the printed collagen cells that they'll be implanting will maintain trans- parency, whether they will degrade and if they do, how long it takes to degrade, and whether they induce inflammation, she said. While some research groups also working on tissue engineering the cornea use a molding method, Dr. Zakaria said that the advantage of using a 3-D printer is it's more cost efficient. The collagen material used is expensive. "If we're thinking about scaling up, you want to reduce waste as much as possible so instead of sub- tractive manufacturing where you cut out the mold and throw away the rest, you use additive manufac- turing, which is 3-D printing where you use exactly what you need," she said. Using the 3-D printer could also mean that when it comes to making the cornea specific for patients, de- pending on their needs and corneal geometry for optimal vision, the cornea could be printed according to the 3-D measurements of their ideal cornea, she said. "This is what we aspire to, but we're not at that level yet, and I think it will be awhile before we get there. I think 3-D printing will evolve over time and will improve," Dr. Zakaria said. She estimates it will be 15–20 years before getting something out in the market. Current alternatives "3-D biometric printed corneas are a strong possibility, and research in this area is important and will hopefully change the way corneal transplantation is practiced in the future," said Eric Donnenfeld, MD, clinical professor of ophthalmology, New York University, New York. "What we have now is quite successful, but there are still lim- itations. We have to rely on donor corneas, we have to have donor fam- ilies willing to make the donation, we have to worry about the viability of these corneas including their health, whether they've had pre- vious surgery or have scarring that may affect results. We don't know if new corneas will match optimally with the recipient bed, and rejec- tion is still a strong possibility that requires long-term use of immuno- suppressant corticosteroids in many patients," he said. Artificial corneas created in the past have had issues of rejection, and they've been incompatible with the patient's tissues, Dr. Donnenfeld added. "Having a biometric cornea that was tissue typed would eliminate the need for corticosteroids, would op- timize the efficacy of the procedure, and would be a step toward mak- ing corneal transplantation a more reproducible and safer procedure," he said. "Patients would have greater access to corneas, and it would obviate the need for eye banking in many cases. "When you think about 3-D printing, this is a technology that didn't even exist 5 years ago, and now it's having significant appli- cations in industry. While it looks to be many years away from being clinically available, it is an interest- ing look at the future of where we are going in ophthalmology," Dr. Donnenfeld said. EW Editors' note: Dr. Donnenfeld and Dr. Zakaria have no financial interests related to their comments. Contact information Donnenfeld: ericdonnenfeld@gmail.com Zakaria: nadia.zakaria@gmail.com

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