Vision (ability)
That which is detected by the five senses; not necessarily understood (imagine looking through fog, trying to understand if you see a small dog or a cat); also that which is detected within consciousness as a thought, intuition, deduction, etc.
Conscious understanding of something.
The organisation, identification and interpretation of sensory information.
Acuity
Strength of vision expressed on some definite scale.
The sharpness of vision or sight.