Corneal Opacity is the "Glazed Eyes" you're referring to. Usually it is
caused by either poor water quality or bacterial infection. I have
successfully treated this by adding a small dose of aquarium salt to the
water. I'm using 1 Tbsp per 5 gallons in a planted tank.

Corydoras catfish can't handle salt so don't go over that figure if you've
got a planted tank.