Understanding the anatomy of the cornea is helpful in understanding the syndrome of pannus. The cornea is the clear part of the globe that covers the iris and pupil. It extends outward with a convex exterior curvature from the sclera or white of the eye. The healthy cornea is clear and has no blood vessels within itself. The cornea receives all of its nutrients from a perpetual bath of tears.
Tears are essential to the normal function and health of the cornea.
The cornea remains transparent as long as the protein of the stroma is perfectly aligned. Anything that upsets this alignment interferes with corneal transparency. The epithelium and endothelium act as barriers for the stroma and help maintain the precise environment for transparency. Pannus is a membrane of small blood vessels and inflammatory cells that cover the epithelium of the cornea thus, obstructing vision much like a window shade. Their is a strong breed predisposition for German Shepherds as well as crosses of Shepherds.