How does blindness operate in Shakespeare's King Lear?

Blindness is a pervasive theme and device in Shakespeare's King Lear. Both Lear and Gloucester, for instance, are blind to the truth when it comes to their children (Gloucester wrongly believes the treacherous Edmund loves him, while Lear also wrongly believes the scheming Regan and Goneril love him more than Cordelia does). As such, both Lear and Gloucester are blind to the truth of things and fail to see reality as it actually is, a mistake that ultimately leads to both figures' downfalls. In Gloucester's case, metaphorical blindness leads to real, physical blindness, as his inability to recognize Edmund's scheming leads to his eyes being gouged out by Cornwall. Ironically, it is only when Gloucester is physically blind that he is able to understand the truth and recognize Edgar as his loyal child. This irony is one of the most important aspects of the play, as it highlights the ways in which trauma or misfortune can lead to sudden insights and epiphanies.