September 2012




Dialing in possible cataract diagnosis

by Maxine Lipner Senior EyeWorld Contributing Writer

Smartphone technology for cataract detection

Worker in India using the CATRA, which can show position, size, shape, and density of a cataract Source: Ethan Solomon

Child in Kenya benefiting from use of the CATRA Source: Edward Wong

Imagine being able to use your smartphone to diagnose your own cataracts. Such is the promise of a new device dubbed CATRA, according to Vitor Pamplona, visiting Ph.D. student, Massachusetts Institute of Technology, Cambridge. The CATRA system, which is akin to a weather radar beam used to sweep the sky for clouds, scans the eye for hazy areas of the lens where a cataract may be brewing. Prior to the CATRA system, Mr. Pamplona and others on the team were working on a similar system known as NETRA, another prototype that used the smartphone to measure refractive error. "That prototype gives you spherical cylindrical (error) and axis of astigmatism," Mr. Pamplona said. "In that case, we were serving approximately 2 billion people who have refractive errors worldwide." However, this was not solving the worldwide avoidable blindness issue. "That interested us because it is a huge problem people are blind, and they don't know that they can be cured," Mr. Pamplona said.

Calling on CATRA

The CATRA device will clip onto a smartphone. "When you use this very close to the eye, the CATRA will have the ability to shoot light rays to different parts of the pupil," Mr. Pamplona said. "The idea is the subject will look at it and if that region has a cataract, the pattern or the image that is being displayed on the phone will get blurred or will disappear." The process is an interactive one, calling on subjects to play with the phone displaying different images, looking for the point at which the image fades away. Using this scanning information, the CATRA can generate a map showing position, size, shape, and density of a cataract. "It's a binary map, so for each part of the pupil you have a 'yes' or 'no' if you have cataracts or not," Mr. Pamplona said. When it comes to density, the system can generate a number to show how far along the cataract has progressed. "You have a value from zero to one, from completely clear to completely blocked for every part of the pupil," Mr. Pamplona said. In addition, the system offers a scattering profile, as well as the "angle of spreading" of the brightness.

Ring of clinical promise

The most common way to get these measurements in a traditional office is with an ophthalmoscope or through use of a slit lamp. This, of course, is reliant on the practitioner's ability to determine when the cataract is ripe for removal. "The problem is this is a function of clinicians' ability to look at it and say that it is severe enough," Mr. Pamplona said. "They don't have information to make a very accurate diagnosisit's qualitative." In that sense, he sees the CATRA as offering more information to the doctor. Although there are other high-end instruments that can transform their readings into the same type of map that is offered by the CATRA, they are expensive. "They cost a lot of money," Mr. Pamplona said. "It would be $25,000 or $50,000 in the U.S., so they're not good for the developing world." He pointed out that as a result, these don't help to solve the problem of avoidable blindness in developing countries. "Ours is much cheaper," he said. "We assume that everyone has a cell phone; the plastic piece that goes on top of this to make it work will cost only $3 or $4." On top of that, this will involve downloading an app, something that Mr. Pamplona anticipates will cost at most $0.99. He pointed out that currently there is nothing readily offering this information on maps. It also offers other advantages. "There's the alternative of checking the progression of the cataract over time because the end users can do this at home, and they can see if it's growing or not if it's becoming more dense or not," Mr. Pamplona said. In particular, this technology lends itself to undeveloped countries where they don't have ready access to ophthalmologists. "[There are] people in the big cities buying this device and going to villages to screen people," Mr. Pamplona said. "Then they go back to the city and file the data into some hospital, and the hospital decides to bring that person to the city to have the surgery done." This can all be done without having to invest a lot of money, he pointed out.

Patients could download the app and if they detected a problem, they could visit a practitioner for treatment, he believes. In the hands of doctors, it could offer more quantitative data. However, this must wind itself through the U.S. FDA, which Mr. Pamplona anticipates will likely take 1 or 2 years. In the end, the workability comes down to the idea that the cell phone has the electronic goods to deliver a reliable diagnosis. "The center for the Hartmann works in the resolution of 10 micrometers, and the cell phone screen has a resolution of 30 micrometers," Mr. Pamplona said. "So you will have in your pocket a device that has only one-third the resolution of a high-end device." Going forward, it is important to start thinking about what else this can be used for, he said. "We have a bunch of other projects in line that can measure, for instance, macular degeneration, dry eyes, and amblyopiaa lot of different diseases that can start giving people a number," Mr. Pamplona said. "Doctors need to say what this number is, and if it goes beyond that, [patients] need to search for an optometrist or an ophthalmologist."

Editors' note: Mr. Pamplona has no financial interests related to this article.

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