Persistent Papillary Membranes are small strands of tissue found in a dog's eyes. They are in fact, the remains of essential blood vessels that supplied all important nutrients to a dog's lens as it first develops while puppies are still in their mother's wombs. In normal circumstances, these strands dissipate and vanish altogether when a puppy is around four to five weeks old, but occasionally they do not.
PPM is an inherited disorder that parent dogs can pass on to their offspring. However, just how the condition is genetically passed on to puppies remains unknown. In a lot of cases, dogs that have remnants of these tissues in their eyes do not experience any problems whatsoever. However, it does depend on where the strands happen to be within the eye and how many of them are in a dog’s eye as to whether they will interfere with a dog's vision and to what extent this may be.
If the strands form a bridge across a dog's pupil, it could lead to corneal opacities which is a clouding in the eye. Should the strands go from the iris to the lens, it can lead to dogs developing cataracts and if they become sheets of tissue in the eye's anterior chamber, it can seriously impact a dog's overall vision.
Certain breeds seem to be more predisposed to inheriting Persistent Papillary Membranes than others and this includes the following although many other breeds can be affected only to a much lesser extent:
The condition is particularly prevalent in the Basenji where the strands form a bridge to a dog's cornea which impairs their vision quite considerably due to the opacity seen in the eye. The condition is sometimes seen along with optic nerve coloboma in the Basenjis too which can also cause dogs to be blind.
Persistent Papillary Membranes are more often diagnosed in young dogs and the signs of there being a problem include dogs having small white spots in their eyes. A vet would need to have a dog's full history before examining their eyes with an ophthalmoscope which would establish if and where any strands might be and whether they are on the cornea or the lens.
For the moment, no treatments are available for dogs suffering with PPM. However, in some instances a vet might recommend using specific eye drops which could help dogs with the condition. If cataracts form on a dog's eyes, they may also recommend surgically removing these as way of improving a dog's vision although it's worth noting that PPM related cataracts do not typically get any worse as time goes by because it is not a progressive disorder.
As previously mentioned, certain breeds are more predisposed to inheriting PPM than others with the Basenji being one breed where careful and selective breeding is essential to reduce the risk of puppies inheriting Persistent Papillary Membranes from their parents. However, breeders should never use any dog suffering from PPM regardless of their breed, in a breeding programme to prevent offspring from being born with the condition.
Breeders should always have their puppies regularly tested by a certified veterinary ophthalmologist when they are around 9 weeks old to ensure they are PPM free. There is a OFA Eye Certification Registry and it is possible to check a dog's status through this service. However, there is no guarantee that a dog would or would not produce puppies with PPM even if they are registered as being free from PPM themselves.
Depending on the severity of their condition, dogs that have inherited the disorder can lead full and active lives because in most cases the condition does not impact the quality of their lives. The other thing to bear in mind is that PPM is not a progressive disorder and therefore a dog's eyesight would not get any worse because they have PPM and that most of the time the strands get reabsorbed and therefore disappear altogether as puppies get older. The good news is that severe cases of PPM are very rare, but should a dog suffer a worse case of the condition, they are extremely adept at adapting to the fact their vision is impaired and go on to lead full and happy lives regardless.