I had a conversation with an eye specialist that promotes several exercises to improve vision, one of them in particular is called "accommodation" which basically consist of the movement of ciliary muscles through contracting and relaxing, this changes the shape of the crystalline lens and therefore blurry vision happens.
He knew about this movement, but was not aware that some people can do it at will, and neither that we can hold the blurred for as long as we wish to.
He knew about this movement, but was not aware that some people can do it at will, and neither that we can hold the blurred for as long as we wish to.