The ever increasing popularity and availability of smartphones and the rapid advances in technology for capturing and sharing images with them have resulted in the expanding use of smartphones as a clinical-imaging device in ophthalmology. This application has been facilitated by the ease of use and portability of the smartphones and the already extensive mobile-phone networks, and it presents a unique opportunity for applications such as telemedicine and self-diagnosis [
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 [
We describe in detail a relatively simple technique of fundus photography in human and rabbit eyes using a smartphone, an inexpensive app for the smartphone, and instruments that are readily available in an ophthalmic practice. The safety of the illumination using this technique with an iPhone 4 in human eyes has been described previously [
Smartphone fundus images were captured with an iPhone 4 or iPhone 5 (Apple Inc., Cupertino, CA, USA) and a 20D lens (Volk Optical Inc., Mentor, OH, USA) with or without a Koeppe lens (Ocular Instruments, Bellevue, WA, USA). By using the coaxial light source of the phone, this system worked as an indirect ophthalmoscope that captured a digital image of the fundus in the smartphone camera [
Filmic Pro app allows independent control of light intensity (red light bulb), exposure (green circle), and focus (blue square) while filming. Video library access (blue arrow).
This technique of smartphone fundus photography involved multiple steps that are described in detail below. The technique is simple, yet it may take a few attempts to master since the user must learn to readjust the filming distance for focusing with the 20D lens while looking into an inverted image of the fundus on the iPhone screen. In addition, since the camera lens is usually located in the corner of the smartphone and the digital display is in the center of the phone, the parallel but skewed alignment necessitated by this displacement required some practice to get the fundus images in the center of the screen (Figure
Filming setup with user holding iPhone for filming with Filmic Pro app in one hand and holding 20D lens for focusing on the retina in the other hand.
Once the app was set to the above parameters, the iPhone light source and camera were used by the operator as an indirect ophthalmoscope to create a digital image. For most images, we used a 20D lens for focusing the light on the patient’s retina in the clinic or emergency room setting. In the operating room during examinations under anesthesia, we also used a combination of a 20D lens with a Koeppe lens, which when placed on the eye was useful in keeping the lids open, the cornea wet, and provided a slightly wider field of view. The app’s video recording was activated, and a video of the fundus was captured on the iPhone screen (Figure
After the video had been exported to the camera roll, the still images were extracted by one of two methods. The first method involved the use of either the app MovieToImage (DreamOnline, Inc., Tokyo, Japan;
It was of utmost importance to maintain the confidentiality of personal data in accordance with the Data Protection Act 1998 and Access to Health Records Act 1990. For protection of privacy, the smartphones used in our institution are encrypted, and the images are transmitted via institutional e-mail with encryption of the attachments.
The described technique of smartphone fundus photography with the use of iPhone 4 or iPhone 5, the app Filmic pro, and a 20D lens with or without a Koeppe lens was able to capture excellent, high-quality fundus images in both children under anesthesia (Figures
Retinoblastoma (partially treated) imaged during examination under anesthesia.
Familial exudative vitreoretinopathy imaged during examination under anesthesia.
Vasculitis imaged in emergency department setting.
Large choroidal nevus imaged in the emergency department setting.
In addition, successful photodocumentation of rabbit fundus was achieved in control and experimental eyes (Figures
Control rabbit eye.
Experimental rabbit eye with induced total retinal detachment and severe proliferative vitreoretinopathy.
High-quality fundus images were successfully captured in human and rabbit eyes using the built-in camera and light source of the iPhone 4 and iPhone 5 in combination with the application Filmic Pro and a 20D lens with or without a Koeppe lens. This technique produced consistently high-quality images because it allowed independent control of the light intensity, the focus, and the exposure during filming. In addition, with the use of the video capture mode with subsequent still-image extraction, high-quality images were obtained even with a relatively short time of video capture, as the best available still images were extracted subsequently. We found that using the combination of the app with video capture was critical to the success of our technique.
The iPhone 4 light source, when used with a 20D condensing lens for smartphone fundus photography using the described technique, had been previously tested and found to be well within the safety standards for human eyes. Kim et al. [
Smartphones are now being used more routinely in ophthalmology to document patient’s ocular conditions [
This technique has been extremely helpful for us in the emergency department setting, in inpatient consultations, and during examinations under anesthesia as it provided a cheaper and portable option for high-quality fundus-image acquisition for documentation and consultation. This technique is well tolerated in awake patients most likely since the light intensity used is often well below that used in standard indirect ophthalmoscopy.
In addition, this technique has been useful in the laboratory to document retinal findings
The currently described system was able to take consistently high-quality fundus photographs in patients and in animals using readily available instruments that are portable with simple power sources. It is relatively simple to master, is relatively inexpensive, and can take advantage of the expanding mobile-telephone networks for telemedicine. We expect that the quality of the images achieved using this technique will continue to improve with availability of higher-resolution cameras with larger sensors and better image stabilization that are being incorporated into newer smartphones.
All authors have no conflict of interests to report.
Shizuo Mukai is supported in part by gifts to the Mukai Fund at the Massachusetts Eye and Ear Infirmary.