Light and electron microscopy of corneal melting syndrome (Mooren's ulcer).

Three patients with corneal melting syndrome of Mooren are described all of whom required lamellar grafting for perforation of the cornea. All these grafts subsequently failed. Tissue excised during grafting was studied by light and electron microscopy. In all cases the conjunctiva contained large numbers of lymphocytes and plasma cells. The limbal cornea showed 3 distinct zones: the deep stroma was intact but contained a prominent macrophage infiltrate; in the mid stroma marked hyperactivity of fibroblastic cells was associated with disorganisation of the corneal lamellae; the outer stroma was heavily vascularised and infiltrated by lymphocytes and plasma cells, with destruction of the collagen matrix. At the advancing, undermined edge of the corneal ulcer the deep stroma was undisturbed, but in the superficial layers accumulation of fibroblastic cells and destruction of collagen was observed. No other cell types were found. All the failed grafts contained fibroblasts which appeared highly active, surrounded by disorganised collagen fibrils. In these patients destruction of both host and graft corneal stroma apparently resulted from the activity of fibroblastic cells.