Any way to reproduce this kind of bloom/lens effect?

[steve_wilson]

The lights in my scene have a grid like structure in front of the light itself but the lens effect isn't taking this into consideration it seems. I can roughly simulate this effect by using an obstacle image but this seems like a bit of a fudge to me. Is there a way to produce this accurately?

[hermit.crab]

To see the individual beams of light, which pass through the grid as in the image, you probably need some kind of atmosphere. This tutorial may help you out.
The image has lens imperfections as well, which you can recreate through the Lens effect's Lens scratches, Lens dust, Obstacle, and Filter image options.