Pseudoexfoliative disease of the lens: a study in electron microscopy and histochemistry

The anterior lens capsule in pseudoexfoliative (PE) disease has been investigated with scanning electron microscopy and transmission electron microscopy. It shows several distinct zones which correlate with those seen clinically. True exfoliation of the anterior lens capsule is shown as an integral pathologic feature of PE disease. PE fibrils are mixed with various degraded cell products, including organelles, of which uveal pigment granules are the most frequent. Sheets of degenerating iris pigment epithelium as well as individual cells are often firmly adherent to the pre-equatorial lens capsule and zonules. PE fibrils on the capsule are 35 to 40 nm in width, often showing several subunit filaments about 10 nm wide. PF filaments forming vertical bundles in the pre-equatorial capsule are 10 nm wide, but show little tendency to aggregate laterally. Histochemical and ultrastructural properties of both types of PE fibril and those of the capsular inclusion suggest that they are closely related fibrillar proteins. PE fibrils share some of the characteristics of amyloid but are not identical substances. Nevertheless, a similar mechanism of synthesis is suggested. The participation of non-lenticular sites in the formation of PE fibrils is not precluded by this hypothesis.