Let's first see the mechanism of working of concave lens for correction of myopia. If a myopic eye has a near point less than infinity say 1 meter(m) then we use a concave lens of focal length 1, so that the rays from infinity appear to come from 1 meter before reaching our eye lens.
Now, consider a scenario where a person with healthy eyes tries to see a object at infinity using a concave lens . Similarly, the rays from infinity would appear to come from 1 meter and the person will be able to see the object simply because he/she can see an object placed at 1 meter clearly without weraring a spectacle.
The argument shows that the a healthy person can clearly see objects at infinity even after wearing a concave lens. However, in real life I don't think this is true. My friends with healthy eye say that the vision is not clear after wearing glasses. Why is it so?