Your vet may prescribe a topical antibiotic and anti-inflammatory medication to reduce the swelling and risk of infection, but it rarely helps in the long term. The most common treatment for cherry eye is surgery.
It was once common for veterinarians to remove the third eyelid altogether; however, this was before the importance of the tear gland was understood. Without it, your dog would require eyedrops for the rest of his life.
Today, your vet will probably recommend surgery to reposition the third eyelid back to its proper location. The most common procedure involves tucking the eyelid back into place and securing it permanently with a stitch.
It’s possible and even common for cherry eye to recur after surgery. If the condition does show up again, let your veterinarian know as soon as possible so you can set up a second surgery to correct the problem.
Sources
Brevitz, Betsy. “The Complete Healthy Dog Handbook.” Workman Publishing, 2009. (April 18, 2011)
http://books.google.com/books?id=DA8Nb56R3qsC
Brooks, Wendy C. “Cherry Eye.” VeterinaryPartner.com. March 27, 2008. (May 20, 2011)
http://www.veterinarypartner.com/Content.plx?P=A&S=0&C=0&A=567
The Merck Veterinary Manual. “Nasolacrimal and Lacrimal Apparatus.” (May 20, 2011)
http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/30107.htm
Petwave.com. “Treating Cherry Eye in Dogs.” (May 20, 2011)
http://www.petwave.com/Dogs/Dog-Health-Center/Ear-and-Eye-Disorders/Cherry-Eye/Treatment.aspx