Persistent Pupillary Membranes By Patricia Doescher Pupillary membranes are strands of tissue in the eye. They are blood vessels, which supply nutrients to the lens of the eye before a pup is born. These strands are usually absorbed after the birth of the puppy and are gone around 4-5 weeks of age. If these strands remain in the eye after this age they are called Persistent Pupillary Membranes and could interfere with vision depending upon their location and degree of effect. They may bridge from iris to iris across the pupil, iris to cornea (which could cause corneal opacities), or iris to lens (which could cause cataracts). It is also possible they could form sheets of tissue in the anterior chamber of the eye. These remnants cause no problems usually, but in some breeds of dogs, such as Basenjis, Chow Chows, Mastiffs, Pembroke Welsh Corgis, and Yorkshire Terriers are seen enough times and have caused enough trouble to be considered an inherited defect and thus are not cleared by the Canine Eye Registration Foundation (CERF), the centralized national registry of board certified, veterinary ophthalmologists, set up as a means to accomplish the goal of eliminating inheritable eye disease in purebred dogs. In Shiba Inus, iris-to-iris PPMs are classified by CERF as a "breeder option" problem. These PPMs occur occasionally in Shibas and are not considered hereditary defects. Of these dogs who have been bred PPMs have not consistently been passed onto their offspring. Although this doesn’t guarantee there will never be a problem 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. As a "breeders option" CERF is leaving that decision to the integrity of the breeder. To check for PPMs the eye must “not” be dilated prior to examination for better detection. There are some breeds recommended to have a preliminary examination prior to pharmacological dilation on the initial examination, but you will need to ask your ophthalmologist to do this for your Shiba Inu. Once the dog has cleared it does not need to be checked again for PPMs. PPMs may be insignificant in Shiba Inus at this point however concerns are that not all Shibas that are certified have been checked prior to dilation, thus owners may be unknowingly exacerbating the condition when litters are planned. By acknowledging the breed has PPMs, making every effort possible to detect them in our breed and finally, making wise decisions in regard to the use of such dogs in our breeding plans, can help prevent the Shiba Inu from becoming another on the list of breeds with problems in this area.