A team in the US has developed an inexpensive, portable Raspberry Pi 2-based camera that can photograph the retina without the need for pupil-dilating eye drops.

The prototype camera – developed by researchers at the University of Illinois at Chicago College of Medicine and Massachusetts Eye and Ear/Harvard Medical School – is made up of readily available parts that can be assembled for around $185.

It has been designed to overcome problems that can arise with pupil-dilating eye drops that are administered as part of eye examinations. These can include the time it takes for the drops to work, several hours of blurred vision afterwards, and a stinging sensation when they are delivered.

“As residents seeing patients in the hospital, there are often times when we are not allowed to dilate patients — neurosurgery patients for example,” said Dr Bailey Shen, a second-year ophthalmology resident at the UIC College of Medicine. “Also, there are times when we find something abnormal in the back of the eye, but it is not practical to wheel the patient all the way over to the outpatient eye clinic just for a photograph.”

The prototype camera can be carried in your pocket, Shen said in a statement, and can take pictures of the back of the eye without eye drops. The pictures can be shared with other doctors, or attached to the patient’s medical record.

According to the University, the camera is based on the Raspberry Pi 2 computer, which is connected to a small, inexpensive infrared camera, and a dual infrared- and white-light-emitting diode. A lens, a small display screen and several cables make up the rest of the camera.

The camera works by first emitting infrared light, which the iris does not react to. Most retina cameras use white light, which is why pupil-dilating eye drops are needed.

The infrared light is used to focus the camera on the retina, which can take a few seconds. Once focused, a quick flash of white light is delivered as the picture is taken. Cameras exist that use this same infrared/white light technique, but they are bulky and often expensive.

Shen’s camera photos are said to show the retina and its blood supply as well as the portion of the optic nerve that leads into the retina. It can reveal health issues that include diabetes, glaucoma and elevated pressure around the brain.

Shen and his co-author, Dr. Shizuo Mukai, associate professor of ophthalmology at Harvard Medical School and a retina surgeon at Massachusetts Eye and Ear, describe their camera and how to assemble it in Journal of Ophthalmology.

“This is an open-source device that is cheap and easy to build,” said Mukai. “We expect that others who build our camera will add their own improvements and innovations.”

“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, ” Shen said. “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.”