PPMs are strands of tissue in the eye, remnants of the fetal membrane that nourished the eyes’ lenses before birth. They usually disappear when a puppy is 4 or 5 weeks, but they sometimes persist. The strands can stretch from the cornea to the iris, iris to iris, or iris to the lens, and they are sometimes found in the front (anterior) chamber of the eye. For most dogs, the strands do not cause any problems; generally, they break down by eight weeks. Otherwise, they can cause cataracts or corneal opacities. Your veterinarian can prescribe eye drops to help break them down.