Text: Jelmer Remmers
Jelmer Remmers is a practicing ocularist. He also works with various researchers at Amsterdam UMC, under the direction of Dr. Hartong, on a range of projects related to ocular prostheses.
Let’s take a step back first. To create something in 3D to To print, you first need 3D data. You can obtain this through digital imaging (MRI/CT) or 3D scanning. This data is then used to create a 3D design. This design process can be done manually, automatically, or somewhere in between (semi-automatically). The process therefore consists of three steps: 3D imaging, 3D design, and 3D printing.
Use AI and algorithms
If there are standard steps that need to be taken in the design process, an algorithm can be written to perform these steps automatically. If these steps are more or less standard but specific in certain areas, Artificial Intelligence (AI) can be used. By “training” the AI program with examples (data), the program “learns” which steps need to be taken in the design process. We call this a data-driven design process. An example of this is the automatic selection of a part of the body in an MRI image. A human can recognize an artery in a black-and-white MRI image, even though its appearance varies slightly from image to image. By manually selecting the artery in thousands of images and using this data to train an AI system, software can now automatically recognize and select these blood vessels.
Research on 3D-Printed Eye Prostheses
These developments are also continuing in the field of ocular prostheses. In 2016, a research group from Leuven published a method for the (manual) digital design of a prosthesis based on a CT scan of an eye socket. This design did not include color, but it was a first step. In 2020, the group from Amsterdam UMC published an example of a fully 3D-printed prosthesis in color, featuring the characteristic fibrous structure of the iris. This demonstrated that the technology was ready for use. This so-called “proof of concept” was also not yet worn by a test subject, as the certification required for this was not covered by the research budget. In 2022, a thesis from TU Delft, in collaboration with Amsterdam UMC, was published on a software tool designed to enable ocularists to independently design ocular prostheses. This tool utilized 3D input and the skills acquired by ocularists.
Research in the Netherlands
In the Netherlands, researchers are also actively working on 3D printing of ocular prostheses. The research group at Amsterdam UMC, in collaboration with Delft University of Technology, is working on developing a method to measure, design, and print ocular prostheses. There is close contact with the researchers who published the study in *Nature*. Exchanges have taken place, and there are regular consultations to identify areas where efforts can be combined. In terms of the printing process itself, there are many similarities. However, there is a significant difference in the area of model generation. The process described in *Nature* focuses on the fully automated generation of a model from start to finish. Because only a small portion of the eye socket can be scanned, the majority of the prosthesis must be designed based on statistical analysis.
The digital design process currently being developed in Amsterdam and Delft is specifically aimed at creating a model that the ocularist can—and must—further refine. Based on a scanned impression, a model is automatically generated, which the ocularist then modifies. Instead of a partial scan of the socket as described in the Nature article, a cast of the socket is made and then scanned. This method yields a complete digital representation of the socket. As a result, no missing information needs to be filled in by a statistical model. Because a cast does alter the shape of the socket to some extent, the impression cannot be directly printed as a fitting prosthesis. The philosophy behind this approach is that you specifically want to utilize the manual skills and experience of ocularists in the process. This also allows you to address more complex situations. By combining the ocularist’s experience with the digital environment, there is no longer a need to search in advance for trial models for the patient. It is then unnecessary to print three versions of the same prosthesis, which would require the ocularist to perform a great deal of grinding work. After all, this “grinding” has already been done during the digital design process. That is a major advantage. It is also expected that more ocularists will begin using 3D printing if they can incorporate their own experience into the process.
Future
Larger patient enrollment studies are currently underway in the United Kingdom, and we can expect new publications from these researchers in due course. At Amsterdam UMC, Ph.D. candidate Emiel Romijn is currently working on a study comparing prostheses based on a 3D model with conventional custom-fitted prostheses. The first patients have already been enrolled in this study.
All in all, there are many developments both at home and abroad in the field of 3D printing of ocular prostheses. All of these developments are aimed at creating better, more comfortable, and more aesthetically pleasing prostheses—with as little inconvenience as possible during the fitting process and, ideally, faster and more affordably. It’s an ambitious goal, but by combining conventional techniques with 3D printing, it’s becoming increasingly within reach.
A British-German research group recently presented its findings in the scientific journal *Nature*. In this study, the researchers take things a few steps further. For the first time, they have combined various techniques to create a prosthesis that was actually worn by ten test subjects. This is not only a remarkable technological achievement but also an organizational one. The research group has, in fact, obtained the necessary certification to bring a new medical device to market.
Recent article in *Nature*
The publication “Automatic Data-Driven Design and 3D Printing of Custom Ocular Prostheses” (Johann Reinhard, Philipp Urban, Stephen Bell, David Carpenter, and Mandeep S. Sagoo) can be read in its entirety via the link below. The research group consists of researchers from the German Fraunhofer Institute, Moorfields Eye Hospital, and the company Ocupeye. This company has patented the entire process. Read more.
You can read a brief summary of this study in Dutch, written by Jelmer Remmers, on the Vereniging OOG in OOG website. Read more.
What is 3D printing?
3D printing is the process of creating a three-dimensional object based on a computer model. In this process, the material is built up layer by layer to ultimately produce an object, such as an eye prosthesis. 3D printing is used in a variety of fields, including industrial design, medical applications, and the arts.
Watch this NTR video about 3D printing of prosthetic eyes.
References:
- Ruiters, S., Sun, Y., de Jong, S., Politis, C., & Mombaerts, I. “Computer-Aided Design and Three-Dimensional Printing in the Manufacturing of an Ocular Prosthesis.” Br. J. Ophthalmol. 100, 879–81 (2016)
- Groot, A. L. W., Remmers, J. S., & Hartong, D. T. Three-dimensional computer-aided design of a full-color ocular prosthesis with a textured iris and sclera manufactured in a single print job. 3D Print. Addit. Manuf. 8, 343–348 (2021).
- Mulder, J. Creating ocular prosthetics using parametric modeling. http://resolver.tudelft.nl/uuid:6f093c02-6405-47bc-832dd74fd2c8714f (TU Delft, 2022)
- Calis, I. A Digital Workflow for 3D-Printed Full-Color Ocular Prosthetics. (TU Delft, 2022).
