A MAN can change the size of his pupils on demand simply by thinking about it.
Doctors have been both astounded and excited about the 23-year-old student’s talent, which is considered “impossible”.
The case is one-of-a-kind, as previous people with this ability have used some kind of strategy in order to change their pupil size.
For example, they would think about looking at direct sunlight to make it smaller, or going into a dark room to make them bigger.
But according to medics at Ulm University, the man from Germany, identified only as “D.W”, doesn’t appear to use any methods.
In an interview, he failed to describe how he does it, telling doctors: “It is difficult to explain, as difficult as answering the question ‘What does it feel like to move a finger’.
“In order to make the change, it requires in any case that I concentrate on my eyes.
"Constricting the pupil feels like gripping, tensing something; making it larger feels like fully releasing, relaxing the eye.
“I have to focus my attention on my eyes and my field of vision and then create the tension/relaxation. This is easier for me to do if I keep one eye closed.
"I can tell that my pupil size is changing because of the change in my vision.”
The pupils change in response to light, focusing, arousal, medication, brain injury, emotion such as fear, and recreational drugs. The function of the pupil is to change how much light is let into the eye.
Muscles in the coloured part of your eye (iris) change the size depending on the stimulus by contracting and relaxing.
The motion is automatic and can’t be controlled – or so doctors thought.
D.W realised that he could change the size of his pupils by himself at the age of 16, when he used to play a lot of computer games.
He would try and “relax” his eyes by rolling them around and focusing and unfocusing them, a case report in the International Journal of Psychophysiology described.
One time, while showing his friend he could “tremble” his eyeballs, the friend told D.W he’d made his left pupil smaller than his right.
After that, D.W repeatedly practised doing this in the mirror or when “procrastinating while doing homework” until he was able to do it more reliably.
He said he doesn’t know how many hours it took him to learn the habit because he had “always liked to play with my vision”.
At first he would focus on objects in order to change his pupil size until he didn’t need them anymore, and would simply “think” about doing it, using only “concentration and relaxation”.
D.W contacted one of the authors who wrote the paper in to tell them about his strange ability, which led them to run tests.
He proved he could dilate his pupils up to 0.09 inches (2.4 millimeters) in diameter and constrict them to 0.03 inches (0.88 mm) in diameter.
What’s more, D.W was able to hold an object very close to his eye and bring it more into focus by constricting his pupil more, even though it was already at “maximum” natural constriction.
He said the sensation is not the same as squinting, which is a “tugging at the back of the eyeballs”.
The researchers did brain scans and discovered that D.W had increased activation in areas of the brain involved in volition, or the ability to decide and do something out of free will, ScienceAlert reported.
The paper concluded: “So far none of potential – conscious or unconscious – indirect strategies, may it be accommodative or vergence efforts or mental efforts and imaginations, could be observed or inferred to be fully responsible, suggesting direct voluntary control of pupil size in the present case.”
Christoph Strauch, senior author and an assistant professor in the experimental psychology department at Utrecht University, the Netherlands, said: "Quite some people have reached out who believe that they might be able to do the same thing – this is really cool.”
How people have previously been described to change their pupil size
Here are some ways you could try and make your pupils change size – although don’t be suprised it if doesn’t work.
Imagine a dark room: Your eyes may dilate for a short period.
Look at a distant object: Focus and unfocus your eyes. Your pupils will change in size as you do it, but only someone looking at you would be able to see.
Tense the stomach: wikiHow says sucking the stomach in and tensing the muscles might make the pupils dilate. It's not clear why some people have this.
Imagine an adreniline rush: The pupils change in response to emotions, including fear.
Imagine sex: Sexual arousal is one of the ways the pupils change size. It's possible you could do this just by thinking about sex.
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