I agree that gluteraldehyde is the best fixative for rodent eye.  For mice,
I've never trimmed them, but for rats trimming is beneficial.  Trimming off
just less than half the eye (leaving the optic nerve on the saved 'half')
saves the lens, opens the eye for better processing/embedding, and keeps
anatomy intact.  Just remember not to trim until after 18-24 hours in
fixative.
Carol Whitinger
Esperion Therapeutics, Inc.