Philosophers have wondered for centuries whether someone who was blind from birth would “see” the world in the same way as people with normal vision. After all, there’s much more to perceiving the world than properly functioning eyes. Think of it: otherwise all you’d need to do is strap a camcorder to a car and you’d never have to learn how to drive!
But there are surprisingly few cases of people who were born completely blind and then had their sight restored after many years of blindness. If a patient can be cured, it’s usually done quite early in life. But a few cases have emerged in recent years, the most promising of which was a woman from India who goes by the initials S.R.D. She was born almost completely blind, able to tell day from night but otherwise unable to perceive anything visually. At the age of 12, she underwent surgery to correct her vision, which was successful in one eye. Almost overnight she was able to experience a whole new visual world, and she has had vision that was correctable to near-normal for the past 20 years.
Although researchers weren’t aware of S.R.D.’s case until recently, her mother told a team led by Yuri Ostrovsky that it took several months for her daughter to be able to recognize basic objects and navigate the world using sight. Eventually she completed seven years of school, married, and now works as a maid. She can get around her town by herself and walks without a cane.
But what Ostrovsky’s team wanted to know was whether S.R.D.’s visual system was truly normal. Using a laptop computer, they gave her ten different tests of the visual system, including visual memory, shape matching, depth perception, face/nonface discrimination, face identification, and gaze estimation. They gave the same test to another woman from India who had accurate vision and the same education level and social status. They also tested several Americans with similar visual acuity to S.R.D. (about 20/200).
Overall, the researchers found that S.R.D. could complete nearly all of the tasks just as accurately as the others, although anecdotally it took her about 5 to 10 seconds longer than the people who had never experienced blindness. There were two exceptions. She wasn’t quite as good at recognizing faces (though she still was more than 75 percent accurate), and she had a peculiar difficulty in judging gaze direction. Take a look at these photos:
For photo 1, S.R.D. would accurately say that I’m looking to the left, just like everyone else would. But in photo 2, she wouldn’t be able to perceive that I’m also looking to the left. She could only judge gaze direction based on head orientation, not eye orientation. Even people with equally poor visual acuity as S.R.D. were easily able to do this task. We’ve discussed gaze direction before, and it looks like what S.R.D. is doing is defaulting to the most basic system for judging gaze — head orientation. People who’ve always had normal vision still make mistakes when the eye-orientation and head-orientation conflict. Somehow S.R.D. just never learned to use eye-orientation when head-orientation is ambiguous.
Still, all in all, S.R.D.’s vision was strikingly normal, even after being completely blind for the first 12 years of her life!
Update: Michael Bach and others bring up an interesting point in the comments. There have actually been several studies of individuals who have had sight restored after being born blind. But S.R.D.’s case is unique because of the length of her visual deprivation and the time that passed since vision was restored. Take a look at this graph from the article:
It shows both of these factors for a number of different studies, and as you can see, in all other cases, either the study was conducted very shortly after vision was restored, or the individual didn’t experience blindness for a very long time. Finding a case like S.R.D.’s is quite unusual!
Yuri Ostrovsky, Aaron Andalman, Pawan Sinha (2006). Vision Following Extended Congenital Blindness Psychological Science, 17 (12), 1009-1014 DOI: 10.1111/j.1467-9280.2006.01827.x