What is persistent pupilary membrane (PPM)?
The pupilary membrane is a fetal structure which covers the pupil prior to birth. Sometimes all or part of it fails to go away, or “persists.” This can occur in one or both eyes. The PPM is made up of iris tissue but sometimes parts of it will attach to the cornea, the clear covering over the front of the eye, or the lens. Most dogs with PPM have functional vision but occasionally there will be moderate to severe vision loss in the affected eye, particularly with corneal or lens attachment.
How do I know if my dog has PPM?
Sometimes it is possible to see PPM yourself, but it is best to have this confirmed by a veterinary ophthalmologist. Since the condition is present from birth it should be noted the first time the dog is examined. If a dog had a clear report and is later found to have PPM, get an additional opinion because someone was mistaken.
Can PPM go away?
Yes. PPM is a developmental error. The pupilary membrane is supposed to go away. Sometimes this process is delayed and a PPM found in a young puppy will be gone by the time it is 6 months old. These are not a problem.
Why is iris-to-iris PPM OK when other kinds aren’t?
The American College of Veterinary Ophthalmologists does not consider iris-to-iris PPM to be significant because it does not cause visual problems for the affected dog. Some PPMs attach to the lens or the cornea where they may cause blinding opacities. Iris sheets may block a significant portion of the pupil, preventing the dog from seeing with the affected eye. This is why iris-to-iris will pass (usually with a notation) but the other types will not.
What do I do if my dog has PPM?
If your dog is diagnosed as a young puppy, the PPM may go away. You should be able to find out by the time the dog is 6 months old. If it persists beyond that point it will be there for life. PPM does not cause your dog any pain. In most cases it does not cause any significant visual problem. Dogs with iris-to-iris PPM can do anything a normal dog might do. However, if the PPM is of a type that limits vision you need to take that into consideration when deciding what kind of activities you want your dog to participate in.
Is PPM inherited?
Yes, though the specifics of inheritance are not yet known.
How common is PPM in Aussies?
This is a common eye defect in Aussies, but the more serious forms are very rare.
What does PPM mean for my breeding program?
Dogs with the more serious forms of PPM (iris sheets or attachments to cornea or lens) should not be bred. Dogs with iris-to-iris PPM may be bred but to be safe it would be best not to breed to another dog with PPM or to mates with a family history of PPM. Don’t repeat a breeding that produces the more serious types of PPM. Parents and normal-eyed full and half siblings may be bred but try to avoid mates with PPM or from families that have a history of PPM.