Below is the node arrangement for making an object emit attenuated light with Cycles and PhysicalSurface nodes.

If you have read my posts above, you will understand that the approach you are using is not very conventional because you are treating the cube as a solid piece of glass.  This means that IOR adjustments will have a very different appearance than using single planes as glass.  That is why you are getting refraction distortions with the camera settings.  You would need to build the scene with 'realistic' props to eliminate unusual render behavior and odd-looking images.