How can I improve eyesight using food without correcting glasses or surgery?
Unfortunately, there really is no way to "organically" improve eyesight in the way I suspect you mean.
Certainly if there has been poor nutrition with vitamin deficiencies/inadequate calorie intake, correcting these will help restore what should have been the default healthy state of the eye. Likewise, omega-3 fish oil and antioxidants will help restore tear production in the case of dry eye, but this almost always a problem of middle-age and older.
Written by J. Trevor Woodhams, M.D. - Chief of Surgery, Woodhams Eye Clinic