Please explain the reoccurring theme subtextual idea of blindness in the play Oedipus. What was the reason behind it Use

Please explain the reoccurring theme (sub-textual idea) of blindness in the play Oedipus.
What was the reason behind it?
Use examples from the play to support your answer.
Be as complete as possible (1-2 paragraphs)
the play is in the attachment.