Vision and Blindness
Symbolism, Imagery, Allegory
We're just going to put this out there right now: any play/novel/story of some sort that features a character getting blinded is also probably saying something about metaphorical blindness. In King Lear, there's a whole lot of talk about literal vision and metaphorical blindness, especially when it comes to fathers "seeing" their children for who they really are.
When Lear mistakenly believes that Cordelia is disloyal and orders her "out of [his] sight," his pal, Kent, gives him the following advice: "See better, Lear" (1.1.14). In other words, Kent implies that Lear is "blind" to the fact Cordelia is the "good" daughter while Goneril and Regan are a couple of evil spawn. We can take this a step further by saying that the root of all Lear's problems is his lack of good judgment – he foolishly divides his kingdom, stages a silly love test to determine which daughter cares for him the most, etc.
Gloucester is equally "blind" when it comes to telling the difference between his "good" son (that would be Edgar) and his bad offspring (that would be Edmund) – Gloucester can't tell that Edmund has manipulated him into believing Edgar wants him dead. Later, Gloucester doesn't even recognize his son Edgar, who has disguised himself as "Poor Tom" the beggar. You can guess where Shakespeare is headed, right? Eventually, Gloucester's eyeballs are plucked out, making his literal blindness symbolic of his inability to "see" the truth about his children.