Poor eyesight simply appears to be a non-reversible ailment among wizards.
We have ample evidence that this is so, by the 19 other mentioned wizard and witches who also wear them.
Amelia Bones (monocle), Borgin (pince-nez), Aberforth Dumbledore, Mafalda Hopkirk
Albus Dumbledore (half-moon)
‘Exactly,’ said Dumbledore, looking very seriously over the top of his
Minerva McGonagall (square)
Instead he was
smiling at a rather severe-looking woman who was wearing square
glasses exactly the shape of the markings the cat had had around
Myrtle Warren (thick lenses), Bob Ogden (thick lenses), Harry Potter (round)
James Potter (round)
The tall, thin, black-haired man standing next to her put his
arm around her. He wore glasses, and his hair was very untidy. It
stuck up at the back, just like Harry’s did.
Rufus Scrimgeour (wire-rimmed), Rita Skeeter (rhinestone), Tofty (pince-nez)
Sybill Trelawney (thick lenses), Arthur Weasley (horn-rimmed)
Percy Weasley (horn-rimmed)
‘I – don’t – want –’ said Percy thickly, as the twins forced the
jumper over his head, knocking his glasses askew.
Wilhelmina Grubbly-Plank (monocle), Eldred Worple
As to Harry's particular case, as Syltherincess states he appears to simply be genetically predisposed to poor eyesight like his father.
With the large base of people wearing glasses in world it leads to a pretty solid assumption that it cant be fixed magically. Not really a plot hole when you look at the vast list of individuals, simply something Rowling planed magic to have no answer to.