NETRA – Refractive eye test using iPhone


I am sure you have been to an eye specialist and got your eye checked.  One of the exam eye specialist conducts is refractive eye test, which is to be done by a computer (auto test) or manually.  In manual test, doctor will show you one lens at a time and will ask you to read letters in a chart or display screen. According to the World Health Organization, uncorrected refractive errors are the world’s second-highest cause of blindness, affecting about two per cent of the world’s population.   

A team of researchers at Massachusetts Institute of Technology (MIT), lead by an Associate professor of Indian Origin, have developed a method to conduct this refractive eye test by using cell phone.  The technique is called NETRA – short for Near-Eye Tool for Refractive Assessment.   Netra in hindi means eyes. MIT team includes:  Media Lab Associate Professor Ramesh Raskar, visiting Professor Manuel Oliveira, student Vitor Pamplona and postdoctoral research associate Ankit Mohan.   

The Near-Eye Tool for Refractive Assessment, or NETRA, is a little device that can be clipped on to a phone.


  • Clip a small plastic device in front of your cell phone screen.
  • Look into a small lens and press phone’s arrow keys so that sets of parallel green and red lines overlap.
  • Repeat the process eight times with the lines at different angles for each eye
  • Software loaded in the phone provides prescription data.

The amazing part is that this whole process takes only 2 minutes.   

What are the advantages of NETRA?
Oliveira said “Our device has the potential to make routine refractive eye exams simpler and cheaper, and, therefore, more accessible to millions of people in...

developing countries.”   

  • Technology will come at low cost to consumer.  You need software to run on the phone and a snap-on plastic device.  Mohan says plastic device can be produced at a cost of about USD 1 to USD 2 but could cost only a few cents more in large quantities.

Has NETRA been clinically tested?
The MIT team is planning to conduct small clinical trial with about 20 people.  The objective tests using camera lenses have shown that it can achieve results comparable to the standard aberrometer test, which shines a laser into the eye and uses an array of tiny lenses to measure its characteristics.   

What are the launching plans for  NETRA?
Africa and Asia is target for initial launch.  The team hopes to produce a more advanced version that will be able to detect other conditions such as cataracts, which could be sold in the developed world as well.   

This cell phone eye examination device fits the bill of countries like India and China.  The innovation is aligned with the business drive corporate giants like GE, which have developed hand help ultra sound machines for Asian countries and call it “reverse innovation”.  I wish the MIT team all the success for their contribution and innovating thinking.

13 Responses

  1. Hello! This is amazing! Really, it is. I am so excited for this!
    I am actually going to Uganda in a week with 500 pairs of glasses, but I have no equipment to test for people’s refraction. We’re literally going to have to do guess and check.

    Is there any way I can get my hands on this application before I leave in a week? (Or even when I’m there.) I am a bioengineering major at Santa Clara University, I can even do a field study to test for the effectiveness of this device in the real world. I would love to explain more about what I’m doing. Please contact me! Email me! Or go to!

    Thanks Sammy

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