So first Jesus talks about not hiding your light under a bucket, then he talks about having your eyes open to God's light, which will then shine through your whole body.
We could slice these two sayings up and consider them separately, but actually I think it's quite interesting to go with Luke's suggestion of putting them together, and seeing what this strange hybrid has to say.
Light is the link between the two halves, but in the first half, the light is shining from us, the believers in Jesus, and it's important for us not to hide it, but put it to good use. In the second half, the light is shining on us, and it's all about whether or not we open our eyes to receive it. Healthy eyes let light flood our body, because the eye is the window on the soul. Unhealthy eyes shut it out, and allow the darkness to breed and fester.
So in fact, there is another common factor - whether the light is blocked. Whether the light is coming from within or without, our job is not to block it, but to let it shine. Our choice is whether to leave the shutters open or closed.
I think back to the arguments with the pharisees, and wonder if Jesus has them in mind. Open your eyes, lads, don't shutter your minds to God's enlightnment.