Open-Source, Ultra-Low-Cost Smartphone Attachment for Non-Mydriatic Fundus Photography - Open Indirect Ophthalmoscope

Abstract

Purpose : We demonstrate an ultra-low-cost fundus photography platform to improve clinical documentation and enable new tele-ophthalmology applications. This consists of a smartphone dongle that costs under $100 that can take non-mydriatic images of the retina with a 45° field of view. In addition, we plan to build an open-source community of ophthalmologists and engineers to drive innovation in low-cost fundus imaging.

Methods : We designed a dual-illumination system consisting of near-infrared (NIR) and visible LEDs arranged in a ring placed around an external camera with the NIR filter removed. Simulations of the ray paths were created using Zemax software to ensure appropriate placement of the LEDs to reduce corneal reflections while providing a high field of view.
In a darkened room, the infrared light (850nm) illuminates the retina without constricting the pupil. This aligns the device with the eye and focuses the retinal image after which a button is pressed that simultaneously produces a flash of visible light and captures a frame from the camera. Hence, this device functions without pharmacologic dilation of the pupil. The live camera stream and the captured image are communicated to the smartphone over WiFi. The entire system is enclosed in a 3D-printed shell that is attached behind the smartphone. The device enclosure was designed using CAD software and holds the electronics.
We ensure scalability of the design through manufacturing as service partners. In addition, we plan to make the designs, instructions, and source codes available on an open platform where engineers and ophthalmologists all over the globe can together iterate to produce improved versions of this device.

Results : The system was successfully tested on a model training eye (Gulden Optics practice eye). The device can take high-resolution images of the retina with a 45° field of view. The entire cost of device along with the disposable 20D lens was $90 without the smartphone platform.

Conclusions : We proposed an ultra-low-cost smartphone attachment for non-mydriatic retinal imaging, and demonstrate an implementation that can be made for under $100 in parts. The images produced by this device appear to be adequate for screening and documentation. We introduce a model for open-source ophthalmology to further drive innovation in low-cost fundus photography.

This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.