Purpose
In limited-resource settings such as developing countries, significant obstacles to ocular imaging include cost and local availability of required instruments. Smartphone photography leverages the ubiquity of mobile handsets to image the posterior pole, but typically requires the use of both hands to hold the device and a lens, which generally must be purchased separately at significant expense. Here, we describe the use of modified, open-source Google Cardboard technology to image the anterior and posterior segment using a head-mounted device composed of materials available globally and at minimal cost.
Methods
A single Google Cardboard device, composed of cardboard and acrylic lenses, was modified with a strap to mount to the viewer’s head. Of the two lenses, each of which has a focal point of 4.5cm (22.2D) the right one was removed from the device and the examiner’s smartphone placed within the device to be centered in front of the left eye. A white LED light and coin cell battery were affixed to the Cardboard to maximize smartphone battery life, and installed superior to the mobile phone camera in order to provide maneuverability comparable to an indirect ophthalmoscope.
Results
This device, plans for which are open source and freely available online, allows the viewer to conduct indirect ophthalmoscopy through a smartphone embedded in the headset, while recording the examination from the perspective of the examiner. The examination is facilitated with a 20D lens, but can also be demonstrated using the detached right 22.2D acrylic lens that is associated with the product, thereby allowing the examiner to perform indirect ophthalmoscopy without costly equipment. Video and clinical photographs of the technique are demonstrated.
Conclusions
Using only a smartphone, cardboard and acrylic, products available in most regions of the world, indirect ophthalmoscopy can be conducted through a headset and images recorded for clinical or research use.