I have a female that is an rd/osd carrier. Found out when doing her first CERF at 26 months. Some carriers have retinal folds, and some do not. Which means CERF will not always detect carriers. So if a carrier is bred (only breed to a clear), some puppies are likely to have folds as well. Folds can be caused by things other than rd/osd. Folds can affect marking ability.
A retinal fold is different from a geographical fold. If it is a retinal fold, then you should complete the RD/OSD test. If the bitch comes back clear, send a request to CERF...they'll give you a breeders option.
If it is a geographical fold CERF will fail the bitch. Dr. Lionel F. Rubin has done extensive research in regards to retinal and geographical folds. I spoke with him personally in regards to geographical folds. He feels that a unilateral geographical fold in the Labrador Retriever is not a problem and he would clear a bitch for breeding. Bi-laterally he would not approve. He says he doesn't see a big problem with geographical folds within the Labrador Retriever breed.
I would contact him before making any decisions. Good luck!
Dr. Lionel F. Rubin
1116 St. Andrews Rd.
Bryn Mawr, PA 19010
610-520-9430