Focus on the front sight. You can only keep one of the three (front, rear, target) in focus no matter what your visual acuity is.
I don't think(?) that a person with 20/20 sees much of a different target than a person with myopia, when they're focused on the front sight. Target's always a blur. It always was for me when I shot with 20/20 as a youngster and the same now with corrective lenses as a geezer.