It could be an ulcer, which would be visible on the surface of the eye, and be unaffected in size and shape no matter the dilation of the pupil. I would expect the rabbit to act painful (squint) and a clear or yellow/green discharge.
If it is only visible in the pupil itself, and looks like a cataract it could be pasteurella- I had a rabbit that had an abscess in the eye itself, and it was diagnosed as such by a vet.
If it is an ulcer/scratch, treat with a non-steroidal ophthalmic antibiotic- if it resembles a cataract, I would cull, as in kill. I would not keep the rabbit as a pet nor re-home it.