Unilateral or asymmetric PEX syndrom?: An electron microscopic study

Background: The pseudoexfoliation (PEX) syndrome which is characterized by the accumulation of an abnormal extracellular material in intra- and extraocular tissues, clinically strictly manifests both unilateral and bilateral. However, the generalized nature of this matrix process does not support unilateral ocular manifestation. The aim of this study, therefore, was a detailed histopathological analysis of the apparently not involved fellow eyes in so-called "unilateral" PEX syndrome. Material and Methods: For transmission electron microscopy, 5 pairs of donor eyes with slitlamp-microscopic, macroscopic and light microscopic evidence of unilateral PEX syndrome and 6 normal control eyes were studied. For immunohistochemistry, light and electron microscopic antibodies against LTBP-1 and HNK-1, two well-known markers for PEX deposits, were used. Results: All apparently not involved contralateral eyes showed ultrastructural changes in the iris, in the ciliary body and in the trabecular meshwork. These changes include deposits of typical PEX fibrils on iris and ciliary epithelia as well as in the iris dilatator muscle, microfibrillar precursors in the periphery of iris vessels, degenerative changes of the iris pigment epithelium and of the dilatator muscle and an increased accumulation of extracellular matrix components around iris vessels, in the dilatator muscle and in the juxtacanalicular connective tissue of the trabecular meshwork. In all contralateral and PEX eyes, but not in the control eyes, LTBP-1 and HNK-1 positive deposits could be identified in the periphery of iris vessels and in the dilatator by light- and electron microscopic immunolabeling. Conclusions: The observed alterations in contralateral eyes in so-called "unilateral" PEX syndrome support the concept that the PEX syndrome is a generalized, basically bilateral disease which may present in a clinically asymmetric manifestation. This should be considered in the clinical management of these patients.