Simple, Inexpensive Technique for High-Quality Smartphone Fundus Photography

Abstract

Retinal photography (fundus photography) is an essential part of ophthalmology practice.Acquisition of high-quality fundus images requires a combination of appropriate optics and illumination usually in the form of a condensing lens and a coaxial light source. This is part of the reason that a commercial fundus camera normally costs tens to hundreds of thousand dollars(Bastawrous A.,2012).

Smart phones are being increasingly used among health professionals(Busis N,2010). Ophthalmological applications are widely available and can turn smart phones into sophisticated medical devices(Mosa AS et al.,2012). Smart phones can be useful instruments for the practice of evidence-based medicine, professional education, mobile clinical communication, patient education, remote patient monitoring or as powerful administrative tools(Mosa AS et al.,2012).

Fundus photography Involves capturing a photograph of the back of the eye i.e. fundus. Specialized fundus cameras that consist of an intricate microscope attached to a flashed enabled camera are used in fundus photography. Fundus photography can be performed with colored filters, or with specialized dyes including fluorescein and indocyanine green (Abràmoffet al.,2010). The optical design of fundus cameras is based on the principle of monocular indirect ophthalmoscopy(Cassin et al.,1990). A fundus camera provides an upright, magnified view of the fundus(Patrick J. Saine et al.,2008). The mobile phone camera can be used to perform indirect ophthalmoscopy when used in conjunction with a + 20D condensing lens. The LED flash of the camera can be used to illuminate the fundus. The flash should be turned on to illuminate and view the fundus. Hence the mobile phone in video mode can be used as a video indirect ophthalmoscope and this technique can be used for fundus imaging(Haddock Lt et al.,2013).

The direct ophthalmoscope directs a focused beam of light into the eye, the reflected light captured by the observer’s eye. By placing a LED light source (powered by an external battery source) close to the camera, the mobile phone can effectively be transformed into a direct ophthalmoscope (Mahesh P Shanmugamet al.,2014).

New device which is a lightweight, 3D printed adapter that directly and reversibly couples iPhones 4 and higher to standard indirect ophthalmoscopy condensing lenses. The attachment can utilize either the phone’s native flash for lighting or another coaxial light source. With both mechanical prototypes and subsequent 3D printed versions of the device, it's possible to quickly photo document a variety of retinal pathologies (David Myung et al.,2014).

A small optical device, which is attached magnetically to a smart phone, is developed to conveniently examine and record videos or photographs of the retina. This attachment, which is called D-Eye, leverages the portability and wireless connectivity of current smart phones, making it possible to acquire retinal pictures even in remote areas (Andrea Russoet al.,2015).

D-Eye works on the principles of direct ophthalmoscopy and exploits the smart phone camera’s autofocus capability to account for a patient’s refractive error. A front negative lens is imprinted in a glass plate, which serves as the top cover nearest the eye. This lens shifts the focus of the smart phone from infinity to −8 cm, in order to exploit the smart phone’s autofocus range of about 18 diopters. This allows for a compensation of refractive error from −12 to +6 diopters. (Andrea Russo et al.,2015).