So, is your eyesight 20/20? Do you have visual acuity?
I have 20/20 eyesight, just had it checked last week. 
The eye charts used were developed in 1862?
Wow, I did not know that. That was a long time ago. One of the oldest professions. 
Yes.  It is. Visual acity is dependent also on the  sensitivity of the interpretive faculty of the brain.
How do they test for that? 
I don't exactly know how they test the interpretative faculty of the brain except for the combination of retinal focus and health of the retina
Any truth to foods helping?
I believe lumine found in egg yolks helps with visual acuity.