When the eyes firmly look at something, they move a little unintentionally. These are microscopic adjustments made by the eyes. At the University of Boston this movement has been studied and they have seen that the eyes can distinguish small details.
The truth is that they have continued with an investigation they conducted 50 years ago. At that time, they saw that with the elimination of the movement of the eyes the image was blurred. The only conclusion that was obtained was that the eyes move constantly so as not to stop the response of the neurons that take care of the vision. Boston scientists believed it would have other functions and so they resumed.