Unable to see anyone’s merits or faults, Lear refuses to look on those who have offended him. Metaphorically he is blind. Ironically Lear banishes Kent from his sight. However, it can be argued that Lear could never really see Kent. He was always blind to Kent’s loyalty to him. It is this loyalty in spite of Lear’s ignorance that makes it all the more important.
As monarch, he is a source of light and life in the Kingdom. When he burns ‘out’ all the characters associated with Lear are ‘left darkling’.
It is appropriate that the play brings them together near Dover in Act 4 to commiserate about how their blindness to the truth about their children has cost them dearly.