Scientists Are Finally Cracking The Code For 3D Printed Eyes

Prosthetic eyes are coming to a printer near you.

A prosthetic eye with detailed iris and red veins against a white background.
Johann Reinhard

For fans of the “howcatchem” mystery subgenre, there was something especially satisfying about Lieutenant Columbo’s trademark squint. As the main character of the iconic police procedural first airing in the 1970s, Columbo’s befuddled expression easily shifted the schlubby, trenchcoat-wearing homicide detective into an all-seeing oracle of crime-solving gotcha, the unwitting suspect trapped in his snare.

His signature squint, however, wasn’t exactly an actor’s choice. At age three, actor Peter Falk’s right eye was surgically removed due to retinoblastoma, and he wore a glass eye for most of his life. Today, it’s estimated over eight million people worldwide wear a prosthetic eye, some due to malignant cancers similar to Falk and others due to severe trauma or to relieve pain in an otherwise blind eye.

While some folks may forgo a realistic prosthetic for a glitzy eyeball instead, manufacturing an artificial replacement is a fairly time-consuming process of bespoke manual labor.

But in our day and age of 3D printing anything (even the dead), one group of researchers is developing a way to make prosthetic eyes as indistinguishable from the real thing as possible. Using non-invasive imaging of a person’s remaining eye and eye socket in combination with some computer modeling, scientists led by Moorfields Eye Hospital in the U.K. 3D printed some impressive prosthetic eyes for 10 individuals who had lost one eye.

The researchers, who published their findings in the journal Nature Communications, say their technique will lend to a more speedy means of manufacturing fake eyes that consistently look and fit just right. The technique may open up accessibility in parts of the world where prosthetic eyes are hard to come by — and improve even high-end bespoke eyes in the process.

The Impact Of Imperfect Eyes

Unlike Falk’s glass eye, most prosthetics today are typically made of an acrylic material called polymethyl methacrylate (or PMMA). The process involves making an individualized mold of a person’s empty eye socket and the cosmetic shell where the iris (the colored part of the eye) and other finishing touches, like veins, are painted on and then polished.

The whole process takes about eight hours of manual work. But since it's all done by hand, even the same ocularist — the technician who makes the prosthetic — could end up making slight variations to the overall appearance or shape that prevent the artificial eye from matching up entirely with its original. Understandably, not having a perfectly realistic-looking and feeling eye can have a real impact on its owner One 2022 study published in the journal Orbit found that people living with an ocular prosthetic experience significant anxiety and depression “correlated with perceptions of the impact of the artificial eye.”

Simplified schematic of an ocular prosthetic in the patient. An orbital implant with the muscles attached is usually implanted in the eye socket after enucleation or evisceration and is covered by the conjunctiva. The prosthetic eye sits between the eyelids and the implant; it can be moved due to friction with the orbital implant.

Johann Reinhard et al., Nature Communications

To that end, the researchers of the new study explored whether it was possible to use 3D printing to create a high-fidelity fake eye.

Between late November 2022 and mid-April 2023, they recruited and made some eyes for 10 individuals who had previously lost one eye, four of whom identified as men and the other six as women. The roughly two-second process involved scanning the empty eye socket to assess its shape (and the remaining eye for color) using a non-invasive diagnostic technique called optical coherence tomography (or OCT). This provided the researchers with a cross-sectional view of the socket’s interior cavity.

One hiccup, however, is that the eyelids get in the way, so it was difficult to render the socket’s entire concavity fully. To get around that, the researchers used some computer modeling to fill in the gaps and predict the perfect shape using data on 173 prosthetics made the old-fashioned way — by hand at Moorfields Eye Hospital in London.

Prosthetic Eyes In 90 Minutes

Once the perfect fit was figured out, the researchers 3D color printed the prosthetics using a material that’s similar to PMMA. The new Technicolor eyes were polished in a tumbler, washed in an ultrasonic bath, and then tested for toxicological concerns before the participants tried them out.

For eight out of the 10 participants, the shape of their new eyeballs closely matched their sockets, although they did need at least one adjustment by an ocularist to secure the fit. For two individuals, their prosthetics weren’t a suitable shape, which the researchers chalked up to technical issues while scanning, or it could have been due to the fact these two participants didn’t have orbital implants, which maintain the space of the cavity.

But the moment of truth: did the new artificial peepers look lifelike? As the color was matched to the existing eye right down to the whiteness of the sclera and the color, size, and structure of the iris, fake and real eyes were nearly distinguishable. (You can be the judge of that yourself with the results down below.) The eight participants with snugly fitting prosthetics ranked the cosmetic appearance of their artificial eye as either excellent or very good (the scale being from unacceptable to excellent); overall facial appearance was rated very good, with a four judging it as excellent.

Pictures of the automatically designed and 3D printed prostheses supplied to the patients. a–h 8 of 10 Patients with their digitally designed, 3D printed prosthesis after adjustments. Patient 1 (a) and Patient 7 (e) have lost their left eye, with the prosthesis shown in the right of the image. Patient 2 (b), Patient 3 (c), Patient 6 (d), Patient 8 (f), Patient 9 (g), and Patient 10 (h) have lost their right eye, with the prosthesis shown in the left of the image. Patients 4 and 5 are shown in Figs. 2l and 3b in the paper.

Johann Reinhard et al., Nature Communications

The researchers say that from end-to-end, manufacturing with their process significantly cuts down on the required manual labor as much as five times. Instead of eight hours, it takes only 90 minutes to print one physically realistic eye and 10 hours to print 100 simultaneously.

This is still a proof-of-concept the researchers are fine-tuning the process with an ongoing clinical trial at Moorfields Eye Hospital. However, they’re hopeful that scaling up the manufacturing could be more cost-effective and expand the accessibility to areas where artificial eyes are hard to come by. They also suggest that with more research and data to improve their computer modeling, some groups who aren’t eligible for prosthetic eyes, like children, could benefit.

While it’s only a cosmetic improvement — not restoring sight itself — it could make a world of difference for some folks who want an eye that looks and feels like the real deal. A 24-karat gold orb, sadly, is not included.

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