Purpose:
Exfoliation syndrome (XFS) is a generalized disorder of the extracellular matrix characterized by the production and progressive accumulation of a white, fibrillar extracellular material in many ocular tissues. Deposits on the anterior lens surface are the most consistent and important diagnostic feature. We compared the structural properties of these deposits and the structure of the lens capsule surface in eyes with XFS to controls without XFS using atomic force microscopy (AFM).
Methods:
The surface structure of lens capsules from eyes with and without XFS which underwent phacoemulsification was studied under aqueous buffer using AFM. The imaging was performed using tapping mode with Si and Si3N4 tips. Samples were also imaged with transmission electron microscopy (TEM).
Results:
Previous scanning and TEM studies of dehydrated tissues had shown that the anterior surface of the lens capsule is composed of a dense mesh of collagen IV fibrils. AFM imaging of hydrated human lens capsule in controls reveals that the anterior surface is covered with thin laminar sheets composed of single layers of parallel fibrils approximately 10-12 nm in diameter. The anterior surface of lens capsules from patients with XFS was covered with a layer of tangled, long (>several microns) fibrils. These fibrils had apparent diameters of ≤10 nm. This XFM fibril layer on top of the lens capsule was confirmed with TEM.
Conclusions:
This is the first study to image fibrils of exfoliation material in a hydrated condition. AFM revealed novel structural details of the anterior surface of the lens capsule and fibers of exfoliation material.
Keywords: pathobiology • extracellular matrix • microscopy: confocal/tunneling