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Remote diagnosis of retinopathy with an easy, low-cost smartphone-based tool

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31 Jul 2020
Remote diagnosis of retinopathy with an easy, low-cost smartphone-based tool

Dr Maximilian W. M. Wintergerst (second from right) trains optometrists at the Sankara Eye Hospital in Bangalore, India.[Image Credit: Universität Bonn/Sankara Eye Foundation India]

With COVID-19 disrupting many healthcare services, this phone-based tool could help diagnose diabetic retinopathy from miles away.

Unmanaged diabetes could lead to many complications, including permanent blindness, in the long run. Diabetic retinopathy is a condition caused when blood vessels of the retina—a thin, light-sensitive layer of tissue present in the back of the eye—are damaged. Across the globe, diabetic retinopathy is the fourth leading cause of blindness, with people in developing countries being the most affected people. A lack of adequate eye care facilities and resources in these regions is thought to be the reason.

India, which is the 'diabetes capital of the world', has about 17% of people with diabetes affected by retinopathy. As the number of people with diabetes is poised to grow, there is an urgent need for affordable screening methods to detect this condition early on, before the damage is permanent.

"If diabetic retinopathy is recognised and treated on time, vision loss can often be prevented," says Dr Maximilian Wintergerst from the University of Bonn. "An important aspect of the therapy is better control of diabetes. Besides, it is also possible to treat the undersupplied retina with laser light before further problems occur."

In a recent study, Dr Wintergerst, along with researchers at the University of Bonn and Sankara Eye Hospital, Bengaluru, has shown how a smartphone-based tool can be effectively turned into an eye-examination device. This device can take not only retinal photos but also detect early signs of diabetic retinopathy. The findings of the study were published in the journal Ophthalmology.

Conventional retina imaging devices are expensive, costing about INR 5 to 7 lakhs, and need specially trained staff to operate them. In this study, the researchers compared the performance of four smartphone-based ophthalmoscopes—a device used to look into the retina and take its photograph. Three of them were based on direct ophthalmoscopy and one on indirect ophthalmoscopy. The researchers compared the image quality, accuracy, and the examination time needed to detect diabetic retinopathy with these four devices.

A direct ophthalmoscope is a simple instrument consisting of a light source, which is shone on an eyepiece to view the retina. While this device is easy to use, only a small area of the retina can be seen. On the other hand, an indirect ophthalmoscope is a compound instrument where the retina is examined through a handheld condensing lens. Although it requires adequate training to use, a larger area of retina can be visualised. 

The researchers scanned 193 people with diabetes, in and around Bangalore, in a field-like setting instead of a hospital. They examined the patients' eyes by filming it with the smartphone-based ophthalmoscopes attached. They trained six optometrists/ophthalmic assistants to use these devices with a mid-range smartphone.

The study found that the indirect ophthalmoscope out-performed others in the image quality, accuracy and time needed to detect retinopathy. It produced the most accurate images, scanned a wider area of the eye at a given point of time, and adhered to the eye-examination procedure. It also costs about twenty-times less than a standard indirect ophthalmoscope.

"The device detected almost 80% of eyes with any retinal changes, even in the early stages of retinopathy. Those eyes with advanced damages could be diagnosed 100% of the time," says Dr Wintergerst about their findings.

India has the second-highest number of smartphone users in the world. Hence, there is a big chance that a smartphone would be available even in the most remote villages. The smartphone-based device, utilised by the researchers, can be used by trained, semi-skilled persons in parts of the country where availability of an eye professional is challenging. It can also be used to take high-quality images of the fundus and sent to an eye doctor, miles away through the internet. The doctor can then evaluate these images and diagnose diabetic retinopathy.

"This modality is promising in increasing the efficiency of screening for retinal changes in diabetics. We now need to expand its deployment with an aim to provide remote screening in the wake of COVID-19 pandemic", says Dr Mahesh P Shanmugam, who heads the Centre of Excellence in Vitreo-Retina & Ocular Oncology at Sankara Eye Foundation and is an author of the study.

This article has been run past the researchers, whose work is covered, to ensure accuracy.