He didn't think this through

Cuz Hermione fixed his glasses and if he tried that he'd probably blind himself

Because frankly, Harry is an idiot.

It's a much more advanced spell, because it's a form of human transfiguration.
Harry would have to change the shape of the eyeballs, and do all sorts of other crazy stuff. It's too risky. Only a professional could do it, and I don't know if there are wizarding optometrists.

His glasses help him get the ladies ( ͡ ͜ʖ ͡ )

Same concept that Arny describes as to why Robert Patrick can't morph into a bomb or gun - too complex.