Both Uses of

focus
in
The Pigman

I remember pulling my hands back to my sides, just keeping my eyes on the stars, concentrating on bringing them in and out of focus.†
Chpt 7 *

out of focus = in a state where something cannot be seen clearly

Then he got even worse, until now his eyes even drift out of focus when you're talking to him.†
Chpt 9

Definitions:

(1) (focus as in: Turn your focus to question #2.)
verb: to concentrate, look at, or pay attention to

noun: the act of concentration, or the ability to concentrate

(to concentrate is to direct attention or effort towards a single thing)
(2) (focus as in: The focus of our study is...)
where attention is concentrated or directed
(3) (focus as in: bring into focus; or out of focus)
a state where something has come into view or can be seen clearly; or an adjustment made to permit a clear view
(4) (focus as with technical usage)
technical usage typically involves some sense of center or concentration such as:
- physics — a point where things come together such as the point where light rays meet
- geometry — a fixed reference point (as of a parabola)
- geology — the point of origin of an earthquake
See a comprehensive dictionary for other less common meanings.