PPM
This is a diagram of PPM.
Persistent pupillary membranes, PPMs as they are often called are common findings on CERF
examinations. They may or may not be a problem in a breed and/or individual dogs. PPMs are
remnants of a fetal structure called the pupillary membrane. This membrane covers the
pupil before an animal is born. It is part of the blood supply to the developing lens (the
structure in the eye that focuses light on the retina). Normally the pupillary membrane
completely absorbs before birth in foals and calves but is partially present and continues
to disappear in neonatal dogs. Absorption may not be complete in puppies when the eyes
first open and small strands or a web-like structure may be seen across the pupil. These
strands normally disappear by four to five weeks of age. In some dogs these strands do not
disappear and become PPMs.
PPMs may be found in several configurations in the anterior chamber (see figure). They may
span across the pupil (iris to iris), from the iris to the lens, from the iris to the
cornea, or they may float free on one end, only connected to the iris. In general, iris to
iris PPMs cause no problems. They may be single strands or a forked structure. These PPMs
may break and become less prominent as the puppy gets older, but they usually do not
disappear completely. Iris to lens PPMs are more problematical. These PPMs cause opacities
(cataracts) at the point where they are attached to the lens capsule. The cataracts do not
usually progress and cause only minor visual deficits. Iris to cornea PPMs cause opacities
on the cornea due to their ability to damage the corneal endothelium (the inner lining of
the cornea). These opacities may be small or may be severe due to the development of
corneal edema (fluid in the cornea). Severely affected puppies (with numerous strands) may
be blind (they may improve as they get older). The strands may regress but do not
disappear.
PPMs are found in many breeds of dog. In most
of these breeds, iris to iris PPMs are classified by CERF as a "breeder option"
problem. This means that most of the PPMs which have been reported in these breeds have
been small and are probably sporadically occurring and not hereditary defects. Dogs with
these small iris to iris PPMs who have been bred have not been reported to have puppies
with vision problems. This does not mean that problems will never occur in these breeds.
Owners with dogs diagnosed with PPMs should be aware of the situation and should probably
either not breed affected dogs or should breed the affected dogs only to unaffected dogs.
In some breeds, PPMs are known to be hereditary and puppies who have any type of PPM will
not receive a certification number. The Basenji is the most well known but CERF will also
not certify Chow Chows, Mastiffs, Pembroke Welsh Corgis, or Yorkshire Terriers with PPMs.
Members of these breeds have been shown to produce offspring with blindness directly
associated with their PPMs. In these breeds, the mechanism of inheritance is not known but
breeding any of these dogs with PPMs is highly discouraged.
a. One end of PPM floating in anterior chamber
- no clinical significance
b. Iris to lens - results in capsular cataract
c. "Y" shaped iris to iris band - no clinical significance
d. Single iris to iris band - no clinical significance
e. Iris to cornea - results in adherent leukoma of the cornea
Love your dog enough to enable future
offspring the ablity to see. CERF your dogs before breeding!!
Constance
Parker
Previous Mastiff Club of America Genetics Data Chairperson-resigned
9-4-98
Editor/Owner Friends of the French Bulldog Newsletter - Health Newsletter
Povrlrd
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Last modified:
March 06, 2011
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