Thanks for bringing up all these thoughts I am actually happy to see your inputs, this was the purpose when I posted in the forum I wanted to find more opinions, let me share couple of the first responses I got when my interest started.
The question was the same, voluntary blurry vision...
1. I am sorry but I am not familiar with the ability that you speak of. It seems that somehow you are able to block the automatic focusing response of the ciliary muscles.
2. It almost certainly does involve the ciliary muscle. Most people, when they are asleep or are placed in a dark room, or are under general anesthesia, put their ciliary muscle at rest. In physiological terms, this means they are slightly contracted vs. the most relaxed state possible, such that about 1.5 diopters of accommodation is induced. Some people, when they “zone out”, are able to manipulate this balance while awake, although their sensorium is slightly altered. Why some folks do this “better” than others is unknown, but that applies to many physical abilities. What makes a great athlete, as opposed to a good, mediocre, or non-athlete? It is not just hours in the gym drive or desire to win, although they all play a part. There are innate differences, between people, and I imagine it is the same for this peculiar talent, involving neurosensory and neuromuscular pathways and controls.
I hope this explanation is of use. I’d be curious as to the ages of those with this ability.
After having these replies I wanted to know further but the moment you brought a simple defocus it simplifies the whole thing, so I will not waste my time anymore.
Many thanks