Can visual acuity be improved?
While there is no such thing as perfect vision, growing evidence from Asia shows that looking often at distant objects (which one does naturally when being outside) can stop myopia progression. Vice versa, progression appears to increase when myopic children mainly live indoors.

D. J. Park, N. G. Congdon: Evidence for an "epidemic" of myopia. In: Annals of the Academy of Medicine, Singapore. 33, 1, Jan 2004, 21–26. PMID 15008557. (Review).

K. A. Rose, I. G. Morgan et al: Outdoor activity reduces the prevalence of myopia in children. In: Ophthalmology. 115, 8, Aug 2008, 1279–1285. DOI:10.1016/j.ophtha.2007.12.019. PMID 18294691.