DESCEMETS-MEMBRANE IN THE IRIDOCORNEAL-ENDOTHELIAL SYNDROME - MORPHOLOGY AND COMPOSITION

The iridocorneal-endothelial syndrome is a disease of the ocular anter ior segment characterized by corneal failure, glaucoma and iris destru ction. Specular photomicroscopical and histological studies suggest th e disorder is caused by a population of abnormal corneal endothelial c ells. In other corneal endotheliopathies Descemet's membrane, the base ment membrane underlying the endothelial cells, is disfigured by the p resence of an abnormal region of extracellular matrix termed a posteri or collagenous layer, which is laid down by the diseased endothelial c ells. In this study we sought to establish the typical morphology and composition of Descemet's membrane in the iridocorneal-endothelial syn drome. Ultrastructural examination of Descemet's membrane in 27 kerato plasty specimens identified three morphologic patterns. In the majorit y there was a posterior collagenous layer which in all cases consisted of an anterior layer of wide-spaced collagen and a posterior layer of microfibrils embedded in an amorphous matrix. In four specimens which did not possess a posterior collagenous layer the anterior banded zon e of Descemet's membrane was absent, In five corneas Descemet's membra ne was normal. The composition of the posterior collagenous layer was examined by immunoelectron microscopy (five corneas) and histochemistr y (six corneas). Collagen Types I, III, V, VI and VIII, fibronectin, t enascin and oxytalan were microfibrillar components, collagen Type VII I formed wide-spaced collagen whilst laminin was present in the amorph ous matrix. The stereotyped derangements of structure and composition identified in the endothelial basement membrane may significantly infl uence the pathobiology of this disorder. (C) 1995 Academic Press Limit ed.