When it comes to eye exams, nobody likes getting the pupil-dilating eye drops. Not only do they sting, but they can also take a while to work, plus they leave patients with blurry vision for hours afterwards. Thanks to a compact new camera being developed at the University of Illinois and Harvard Medical School/Massachusetts Eye & Ear, however, those drops may become a thing of the past.

Ordinarily, the eye drops are required in order to keep the pupil open, so that the ophthalmologist is able to see through it to the retina. Without the drops, the iris muscle would reflexively close the pupil when it was exposed to a strong visible light source … a light source that's needed, of course, to see the retina.

The experimental new camera gets around this limitation by using infrared light to focus on the retina – the iris doesn't react to infrared, so the pupil doesn't close. When it's time to take the actual photo, a very quick flash of white light is used.

Although there are already other cameras that use this infrared/white light approach, they're generally quite large and cost thousands of dollars. By contrast, the new device is reportedly small enough to be carried in a pocket, and is made from parts that cost a combined total of about US$185. Those parts include a Raspberry Pi 2 microcomputer, an inexpensive infrared camera, an LCD screen, plus infrared and white-light LEDs.

"The device is currently just a prototype, but it shows that it is possible to build a cheap camera capable of taking quality pictures of the retina without dilating eye drops," says U Illinois' Dr. Bailey Shen. "It would be cool someday if this device or something similar was carried around in the white-coat pockets of every ophthalmology resident and used by physicians outside of ophthalmology as well."

Shen and co-author Dr. Shizuo Mukai describe how to build the open-source camera in a paper recently published in the Journal of Ophthalmology.