When it works, the key seems to be relaxing the eyes and surrounding muscles while viewing objects at a distance which causes just enough blur. Within a minute or two, the brain's visual cortex figures out a "software compensation" for the signal coming from the eye, which lets the eye stay relaxed instead of straining to focus. More info on Vision Therapy is available from behavioral opthalmologists, but it takes time, motivation and may not be covered by insurance.
[1] https://youtube.com/user/cliffgnu
[2] https://drive.google.com/file/d/0B5REdzibAJQ4VFJuWnZCU3dLcHc...
[3] https://dspace.mit.edu/openaccess-disseminate/1721.1/105363