It is important to realise how blindness, both literal blindness and metaphorical blindness, are linked to two of the most important figures in the play: Gloucester and Lear. The parallels between these two characters are self-evident. Both have children that are loyal and some that are disloyal, both show themselves to be "blind" to the realities of which are loyal and which disloyal, and both end up selecting the disloyal children to be their heirs. It is therefore highly ironic that it is only after Gloucester has been struck blind and Lear has become insane that both realise the error of their ways and see the mistake they have made. In blindness they can "see," and in insanity, they can think sanely. One of the play's poignant moments comes in Act IV scene 6 when Lear and Gloucester meet and bemoan their situation. Note what Lear says to Gloucester:
If thou wilt weep my fortunes, take my eyes.
I know thee well enough; thy name is Gloucester.
Thou must be patient. We came crying hither.
Thou know'st the first time that we smell the air
We wawl and cry....
Thus blindness is an important theme throughout the play and principally in how it relates to Gloucester and Lear, linking them in their tragedy and haunting them with the wrong decisions they have made.