Low-Cost Binocular Indirect Ophthalmoscope Made with CAD Software & Bambu Lab X1C

3D printing is increasingly used in the fabrication of diagnostic equipment, including ophthalmology, which is a medical specialty that deals with the diagnosis and treatment of eye conditions and diseases. A team of researchers from the Department of Ophthalmology at Loma Linda University in California recently published a paper in the Journal of Ophthalmology about their work to develop an affordable, compact binocular indirect ophthalmoscope (BIO). They used a Bambu Lab consumer 3D printer, CAD software, and off-the-shelf electronic and optical components to reduce both the size and cost of the instrument.

BIOs are used to diagnose and manage retinal diseases, but commercially available ones are often bulky and expensive, which makes it difficult to use them in settings where resources are limited. Fortunately, 3D printing and CAD have become more accessible and affordable over the years, which is why the research team chose these technologies to make their own compact, lower-cost BIO.

The researchers used Autodesk Fusion 360 to design the 3D printed parts for the BIO, and OrcaSlicer to prepare the files for 3D printing.

“OrcaSlicer was chosen over Bambu Slicer because of OrcaSlicer’s calibration and filament configuration options,” they explained.

The optics housing, temples, and frame were 3D printed out of acrylonitrile styrene acrylate (ASA), while polyethylene terephthalate glycol (PETG) was used to print the window for the instrument’s charging light. Thermoplastic polyurethane, or TPU, was the material of choice for the eyepieces, charge cover, LED holder, and nosepiece washer. All of the non-3D printed parts are available online.

3D printing can often be a less expensive manufacturing choice for products like this, but the researchers used the Bambu Lab X1-Carbon 3D printer. This $1,449 machine, and some of the extremely durable materials used, called the accessibility aspect of this project into question. However, including the X1-Carbon 3D printer, the total cost of the tools used to build the BIO was $1,707.20, while the cost of all necessary components was $182.26, for a grand total of $1,889.46. A commercially available Keeler Vantage Plus indirect ophthalmoscope costs $4,423.00, so that equals a savings of roughly $2,533. They did also say that very resource-limited settings could use the $349 Bambu Lab A1 Mini and PLA for this BIO, but noted that it “would be less durable.”

The researchers said that ophthalmologists who have some electronics experience should be able to print all the necessary parts in less than 5 hours, and use a soldering iron and small hand tools to assemble it within 2-4 hours. The optical system is made up of:

• eyepieces that can hold different power lenses, like +2D, to correct for a patient’s refractive error
• moveable mirrors for each eye to accommodate different interpupillary distances
• central mirrors that slide to the front and back to adjust stereopsis (binocular depth perception)

A nice feature of this 3D printed spectacle-style BIO is that the battery is incorporated into the frame, which makes it even more compact and manageable. The researchers made the temples in different shapes and sizes to accommodate multiple head sizes and face shapes, and the nosepiece is adjustable.

The lighting system is made up of a 5 mm warm white LED, iris diaphragm, and plano-convex lens, which together produce a circular spotlight that can be tilted from 0 to 10° down; its size can be changed from 2 to 6.5 cm. A pulse-width modulation board and dimmer knob control the light’s intensity, and a 400 mAh lithium battery (charged via a USB-C port) powers the system.

To comply with safety standards, the team used a spectrometer to measure and evaluate the ocular light safety of the BIO. They report that the quality of the retinal image with their device is “comparable to commercially available indirects.” Additionally, it has a slightly larger field of view due to a shorter vertex distance than commercially available spectacle-style BIOs offer.

The 3D printed BIO was intended for clinic usage, but its comfortable and cordless design could make it a good option for scleral buckling or choroidal biopsy surgeries. The research team hopes that by making all of the parts available online, other ophthalmologists will consider making their own 3D printed BIOs, and even improving on the original design; for instance, wireless video recording or an incorporated blue light filter could make this compact instrument even more useful.

“3D printers and CAD programs allow for rapid prototyping through an iterative process, and they are becoming more affordable and easier to use. These advantages helped us create a low-cost, lightweight BIO with the battery incorporated into the frame,” the researchers concluded. “We expect that 3D printing will lead to additional improvements in existing devices in ophthalmology (such as the BIO), as well as the production of novel devices in our field.”

The Loma Linda University research team’s 3D printed BIO met the standards for indirect ophthalmoscopes set by the International Organization for Standardization, and complied with the American National Standards Institute’s light hazard protection requirements for ophthalmic instruments.