Surveillance for diabetic retinopathy is established best practice for patients with diabetes since the Early Treatment Diabetic Retinopathy Study in the 1980’s demonstrated the benefit of timely detection and treatment of diabetic retinopathy in reducing vision loss and blindness due to diabetes.
Unfortunately, access to and uptake of comprehensive eye examinations is suboptimal, particularly in remote communities. Consequently, retinopathy screening programs emerged with the development of non-mydriatic retinal fundus cameras, where retinal images were first captured using Polaroid film and later using digital imaging devices. Non-mydriatic retinal imaging technology has improved considerably with purchase costs decreasing and operability becoming more automated.
The main limitations of commercially available non-mydriatic retinal fundus cameras are the captured field size, inability to detect early macular oedema and the minimal pupil diameter required for acquiring gradable retinal images, generally in the range of 3.3 to 3.5 mm. Over the last decade, scanning laser systems have been developed that can image through smaller pupils (2 to 2.5 mm) and provide wider single exposure fields of view of the retina (up to 200 degrees), but these are costly and not portable. More recently, portable retinal imaging devices using smartphone technology for retinal imaging have been developed and are being evaluated. Earlier detection of diabetic macula oedema with newer technology using Optical Coherence Tomography is now possible, but increases overall screening costs substantially.
In conclusion, the next major step in advancing image-based screening for diabetic retinopathy at the scale needed to make a significant impact on diabetes-related blindness globally, is the development of a retinal imaging device that can image through a pupil diameter of less than 2.5 mm, provide a wide field of view of the retina in a single exposure (greater than 60-degrees) and can provide automated assessment of both diabetic retinopathy and macula oedema. Ideally, such a device would be portable, easy to use and affordable.