Pseudoexfoliation syndrome with poorly dilating pupil: a light and electron microscopic study of the sphincter area

The study was carried out to examine histological changes in the iris sphincter muscle and surrounding tissue in eyes with pseudoexfoliation syndrome (PXS).

Seventeen patients with PXS, 14 of them having capsular glaucoma, were enrolled into the study. Iris biopsies were obtained during extracapsular cataract extractions (ECCE) requiring sphincterotomies. Thirteen biopsy specimens underwent histological examination by light microscopy, and four were examined with the electron microscope. Three iris biopsies from cadaver eyes and one obtained during ECCE from a patient with a miotic pupil (no PXS) served as control specimens on light microscopy. Electron microscopic controls included three iris specimens from cadavers.

In the light microscopic examination, blood vessel walls were stained with Congo Red in seven of the 13 PXS specimens. In three of these seven specimens the stromal tissue was extensively fibrotized, and in two specimens fibrosis was moderate. Distinct stromal fibrosis was also observed in one and moderate fibrosis in two PXS specimens negative for amyloid. The control specimens were not positive for Congo Red, but stromal tissue was moderately fibrotized in one specimen. Light microscopy did not reveal differences in muscle tissue between PXS and control specimens. Electron microscopically, however, the muscle tissue was fibrotic or disorganized in three PXS specimens and in one control specimen. Fibrils, similar to the fibrillar component of pseudoexfoliation material described in previous studies, were found in intimate association with the capillary basal lamina in all of the PXS specimens showing muscular fibrosis.

These findings support the theory that PXS is associated with amyloid, and in some PXS eyes miosis is connected with degenerative changes both in the stromal tissue and in the muscular layer of the iris.