Light microscopy of the exfoliation syndrome

The exfoliation syndrome affects all structures of the ocular anterior segment, as well as the conjunctiva and occasionally, nonocular structures. The exfoliative material has been shown by a series of light microscopic and gross anatomic studies to be only loosely adherent to the anterior lens capsule, zonules and anterior vitreous face, and firmly adherent to the equatorial lens capsule and posterior epithelium of the iris and the nonpigmented ciliary epithelium. Electron microscopy demonstrates that, in these latter regions, exfoliation material consisting of characteristic, cross-banded fibrils embedded in an amorphous matrix, is present both within the epithelial cells and associated with a disorganized, reduplicated basement membrane. These findings suggest that the material arises from the epithelium of the lens, iris and ciliary body, possibly the result of an underlying metabolic disorder. From these areas, the material enters the aqueous humor and later deposits on the anterior lens capsule, zonules, vitreous face, anterior surface of the iris, and trabecular meshwork. Histochemical studies demonstrate the presence of glycosaminoglycans, which may comprise the interfibrillar portion of the exfoliative material. Other studies demonstrate histochemical similarities between exfoliative material and zonules and are supported by recent work suggesting that the exfoliative fibrils are related to the microfibrillar portion of elastin. Although some reports suggest similarities between exfoliative material and amyloid, a majority of histochemical studies do not support this possibility.