Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Meesmann corneal dystrophy ?
    ### Response:
    Meesmann corneal dystrophy is a rare genetic condition affecting the epithelial membrane of the cornea. A slit-lamp examination of the cornea shows diffuse clusters of tiny round cysts in the epithelial membrane.  Over time these cysts can rupture and cause erosions.
    