Jesus speaks of being the light of the world who was sent by the Father to a man who can't see who he then heals (recreates) via the pool of Siloam which we're told means 'Sent' and then as Jesus slips off stage until the end of the story we see the man sent into the den of the Pharisees where he means those who can't see.
The Synagogue can't see because (1) it has already legally committed itself to saying that Jesus can't be the Christ (which is the centre point of the telling of the story) and (2) they prove themselves to have missed the point of Moses whom they claim to follow but who should have led them to see Jesus (ch5), instead they leave the sent one astonished at their inability to see, and then they throw him out - a man whose sent life is surely 'prophetic' of what will happen to Jesus before John's Gospel is finished.
As Jesus returns to the man he finally gets to see the one who was sent to give him sight - he was in darkness but now he's light, while those who thought they were enlightened have only been proven to be blind. Those who know they can't see can be remade as they recognise Jesus' voice (chapter 10 which follows on seamlessly).
And so we're left to see that as the Father sent Jesus so he sends us. Jesus came to us in our blindness and sends us to the blind - some of whom will see that they can't see and recognise the beauty/majesty/life/light/love of Jesus, while some who think they can see will become all the more blind and opposed to Jesus.
Nonetheless the one who was sent to us sents us since 'my sheep hear my voice' - and this is Jesus' chosen way for that to happen - his voice must ring out, or to flip back to the original picture - as the light was sent to shine in the darkness, now those who lived in darkness are light and are themselves sent as light, however dark the setting and however little he is recognised and received, knowing that the darkness might kill the light but it wont overcome the light. The light of the gospel was heard and seen by us, the light that was sent sends us to be light, and that light will be life to those who see and believe. As it was for him, so now it is for us.