How will presbyopia affect distance vision in a person with perfect eyesight? Will he now see 6/12 instead of 6/6 or something?

Presbyopia only affects vision at near and intermediate distances in an otherwise normal eye.

This may not be the case, though, if there is any latent hyperopia (a different and much less common type of farsightedness than presbyopia), cataract formation, or other possible eye diseases.

Jay. Trevor Woodhams - Chief of Surgery, Woodhams Eye Clinic