Smartphone fundus photography: a narrative review

BACKGROUND: The idea to use smartphone for fundus photography was put forward in 2010. Over the last decade, there has been a dramatic development in this field. This narrative review focuses on the principle of smartphone fundus photography, how to master this technique, problems encountered by the beginners, camera applications/devices designed for this purpose and the safety profile of smartphone flashlights for retinal photoreceptors. DISCUSSION: Smartphone fundus photography using a condensing lens is based on the same principle as indirect ophthalmoscopy. Smartphone flashlight serves the purpose of light source or illuminating system. Real and inverted image of the retina is focused by the smartphone camera after adjustment of the filming distance. Beginners can face difficulties like adjustment of the filming distance, glare from condensing lens and reflection from the ceiling lights. Mobile camera applications and holding devices designed for this purpose can help the beginners to address these difficulties. There have been safety concerns about photo-biological risk for retinal photoreceptors by flashlight. Although the spectral irradiance on the retina, while using smartphone for fundus imaging is within the safety limits set by ISO 15004-2.2. The safety profile of latest model flashlights which deliver more power compared to older flashlights, need to be assessed. CONCLUSION: Smartphone fundus photography is a cheap, cost effective, portable and a convenient method for retinal imaging. With practice and use of smartphone camera applications designed for this purpose, the beginners can master this technique. By training young ophthalmology residents and ophthalmic primary caretakers, this retinal imaging technique can be utilized for artificial intelligence, patient diagnostic and educational purposes.