A US team has devised a smartphone system for capturing high quality photos of retinas to help diagnose eye diseases. The cheap and easy-to-use system could bring the advantages of affordable telemedicine to ophthalmology clinics.
The researchers, from Massachusetts Eye and Ear, a teaching hospital of Harvard Medical School, describe the new system and how they tested it in a recent online issue of Journal of Ophthalmology.
The study evaluated the smartphone system's ability to capture photographs of the "fundus," or retina, in human and rabbit eyes.
The equipment comprises a smartphone running an inexpensive app and instruments that can be found in any ophthalmic practice.
Taking photographs of the retina is an essential part of any ophthalmology practice. But current methods rely on fundus cameras that cost tens of thousands of dollars.
Such high price tags are out of reach for many small practices, especially in poorer countries.
The advent of smartphones is starting to change this. These cheap, mobile devices, armed with cameras of increasing quality, are now being used more and more by ophthalmologists to document eye conditions in patients.
'Cheaper and portable option'
Previous studies using Apple's built-in camera app in the iPhone have concluded its video capture is not good enough, as it cannot independently control focus and exposure during filming, which produces glare and results in poor images.
But the system the Massachusetts Eye and Ear team used overcomes this by using an iPhone 4 or iPhone 5 with a more advanced smartphone app, called "Filmic pro," which allows for independent control of focus, exposure and light intensity during filming.
They tested the smartphone's ability to capture retinal images with a 20D lens, with or without a Koeppe lens - a special dome-shaped lens ophthalmologists use to get a direct view of certain parts of the eye, for instance the chambers that are involved in regulating pressure in the eye.
"By using the coaxial light source of the phone, this system works as an indirect ophthalmoscope that creates a digital image of the fundus," they write.
After recording high-definition videos of the fundus or retina, the team was able to extract high-quality still images from the footage.
"Excellent images were acquired with the 20D lens alone in the clinic, and the addition of the Koeppe lens in the operating room resulted in the best quality images," they note.
They tested the system on children under anesthesia, awake adults, and rabbits, and they conclude the 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."
Senior author Dr. Shizuo Mukai, a retina specialist at Massachusetts Eye and Ear and associate professor of Ophthalmology at Harvard Medical School, says:
"Our technique provides a simpler and higher quality method to more consistently produce excellent images of a patient's fundus."
He explains that the system has already proved useful in the emergency department, in consultations with in- patients, and during exams under anesthesia.
It provides "a cheaper and portable option for high-quality fundus-image acquisition for documentation and consultation," he adds, noting that it is also well tolerated in awake patients, something he attributes to the fact the light intensity is "often well below that which is used in standard indirect ophthalmoscopy."
Technique 'simple to master'
The team says even first year ophthalmology residents were able to master the new system quite quickly.
Dr. Mukai adds:
"This technique is relatively inexpensive and simple to master, and takes advantage of the expanding mobile- telephone networks for telemedicine."
He also expects the image quality will improve as smartphones with higher resolution cameras gain larger sensors and improved image stabilization.
In 2011, Dutch researchers who carried out a feasibility study of remote diagnosis via camera phones in Uganda, suggested that a 2 megapixel camera would be good enough to capture a clear microscopy image that could be sent to a website for confirmation and additional analysis by a specialist.
And more recently, another group in the US has created a portable smartphone "microscope," which can detect viruses and material less than one-thousandth of the width of a human hair.