Probably polygenic like entropion. A scroll-like curling of the cartilage of the third eyelid, usually everting the margin. This condition may occur in one or both eyes and may cause mild ocular irritation. The mode of inheritance is unknown. Pigmented cysts arise from the posterior pigmented epithelial cells of the iris and remain attached or break free, floating as pigmented spheres of various sizes and pigments in the anterior chamber.
Some cysts tend to adhere to the posterior surface of the cornea.
Rarely, cysts may be numerous enough to impair vision. The mode of inheritance is unknown. These strands may bridge from iris to iris, iris to cornea, iris to lens, or form sheets of tissue in the anterior chamber. The last three forms pose the greatest threat to vision and when severe, vision impairment or blindness may occur. In all breeds studied to date, PRA is recessively inherited.