How does one tell the difference between not being able to see, and just not noticing?

Vision testing: This is a somewhat metaphysical question- if i don't notice something, have i truly seen it? But, medically, the most important thing is to evaluate the vision function- essentially, to be able to visually resolve a standard image in the way we expect. Visual testing is straightforward; the rudimentary test can be done at pcp, while an ophthalmologist can test in more detail.

Eye test !!: Have your eyes seen to by an ophthalmologist or at least an optician.