“How do you fix a weak eye?”

An examination will determine the cause and treatment.

https://www.aao.org/eye-health/diseases/amblyopia-lazy-eye
Frank Cao

Be more specific. Can you see well at distance, but not near? Or vice versa? Is this a NEW symptom or always been this wa? Will glasses clear up your vision? Has it always been weak or is this something new? Your symptom is so vague that it is difficult to specify a disorder and potential treatment. There is a lineage of disorders that come to mind: Presbyopia, Astigmatism, disease of the cornea, lens, retina, optic nerve or Occipital Cortex of the Brain. Obviously, you need to see an ophthalmologist for specific diagnosis or treatment.

Roger Ohanesian, MD

Weak eye is not a medical diagnosis. See an ophthalmologist.