According to my source,
http://www.solarviews.com/eng/oort.htm, it exists as a (realatively) spherical cloud around our solar system at the very edge of the Sun's gravitational influence. 3 light years away. Or roughly 2.8*10^13 kilometers. Can we see that far? Maybe, but I really doubt it. Or are you asking if the cloud would
eventually interfere with our sight?
EDIT: Oh, you mean why can we see other galaxies/solar systems? I dunno, I've never taken astronomy.