How does horizontal to movement of our eye ball help us focus on distant objects?

Question

How does this work?

What is the near point and how to find the convergence angle when we focus on a distant object.

Is it possible to create an instrument, on the basis of the eye ball, to measure the distance of an object.

Answer 1

Hmm, that's quite a collection of questions.

Near point means the closest point at which an object is in focus.  When your eyes are looking at something at that point, they are turned in = they are cross eyed.  To focus on something in the distance, your eyes rotate horizontally to focus at infinity = the convergence angle is zero.

I'm sure it is possible to make an instrument that uses your eyes to determine the distance - I would guess that that is how range finders for shooting work - but I don't know how such an instrument might be made.