Persistent Pupillary Membranes (PPMs)

Persistent pupillary membranes (PPMs) occur secondary to the incomplete resorption of embryonic lenticular vasculature, a process which is usually complete by several weeks after birth but which may continue for several months in some dogs. Occasionally, the remnants of this process may be recognized as a collection of fine, punctate, tan to brown spots on the axial anterior lens capsule. PPMs may extend from iris to iris, iris to lens, iris to corneal endothelium and/or extend to float feely into the anterior chamber. The condition may be unilateral but is more commonly bilateral. Large or multiple PPMs may result in corneal opacification (due to endothelial damage, traction & fibrosis) and/or secondary cataract formation. Commonly affected dog breeds include the Basenji, Pembroke Welsh Corgie, Mastiff & Chow Chow.