High resolution three-dimensional reconstruction of the collagenous matrix of the human optic nerve head

Abstract

a b s t r a c tGlaucoma is the second most common cause of blindness worldwide, leading to irreversible loss of vision. Prior studies indicate that ocular pressure-induced displacement of the lamina cribrosa (LC) may be responsible for retinal ganglion cell axon damage inside the neural canal. We present a novel approach to imaging the entire lamina cribrosa and the scleral canal at high lateral and axial resolution by using a combination of array tomography and nonlinear optical imaging of serial ultrathin orthogonal sections to detect second harmonic generated (SHG) signals from collagen. The resulting images can be analyzed individually or combined to form a three-dimensional reconstruction of the lamina. Due to the specificity of SHG generated from collagen the density and distribution of collagen inside the scleral canal can be objectively quantified with a high degree of accuracy. The reconstruction shows a non-uniform distribution of collagen along both the longitudinal and orthogonal axes. Mapping the collagen density by geographic region reveals significant differences in collagen content that result in "thin spots" with low collagen density as well as areas of very high collagen content. This suggests a non-uniform mechanical stiffness across the lamina that may account for increased axon damage observed in glaucoma patients. The inferior temporal region of the ONH in particular is marked by low collagen density, which corresponds with clinical observations identifying this region as being more susceptible to damage during the onset of glaucoma. Further application of this technique will help characterize the relationship of age, race and gender on the morphology of the LC.

Tau Accumulation Causes Mitochondrial Distribution Deficits in Neurons in a Mouse Model of Tauopathy and in Human Alzheimer's Disease Brain

“…This technique was developed for synapse analysis in mice [32][33][34] and has subsequently been adapted for use in zebrafish, 55 songbirds, 56 and on one case of collagen imaging in a human optic nerve. 57 We demonstrate that in human brain, array tomography can be used for analysis of mitochondria and other structures at or near the limit of z-resolution of conventional microscopy, adding an important tool in the arsenal of neuropathological analyses.…”

The collagen fibril architecture in the lamina cribrosa and peripapillary sclera predicted by a computational remodeling approach

“…The biomechanical properties of eye tissue were derived from the single crimped fibril via the collagen Fig. 11 a Collagen density map of the human optic nerve head (Reproduced from Winkler et al 2010). b Regional predominant laminar beam orientations obtained from the three dimensionally reconstructed monkey lamina cribrosa (Reproduced from Roberts et al 2009).…”

“…It was observed in earlier studies that the scleral canal was surrounded by a circumferentially oriented ring of collagen existing in the PPS (Goldbaum et al 1989;Morrison et al 1989). Recently, Winkler et al (2010) detected the existence of a distinct ring ("annulus") of collagen fibrils around the scleral canal by recording second harmonic generated signals. The extracellular matrix in the LC forms, as can be observed in light microscopy, apparently a plate-like arrangement with a sieve-like structure leaving enough space for axon bundles passing through the LC (Hernandez et al 1987).…”

The Optic Nerve Head as a Robust Biomechanical System

“…The authors' models represent an acute increase in IOP and therefore the conclusions of this study should be interpreted as giving insight only into the acute effects of IOP and not into remodeling or aging processes. [10][11][12]34,39,[53][54][55][56][57][58] The models in this study did not account for LC microarchitecture, which in humans is not fully characterized, 44 but that animal models suggest may alter the local levels of IOPinduced stress and strain(Kodiyalam S, et al IOVS 2009;50:AR-VO E-Abstract 4893). 17,18 The authors are developing FE models that incorporate more realistic anatomies (like the variations in scleral shell thickness 59 ), material properties (anisotropic and nonlinear scleral properties, 29,33,49 lamina cribrosa anisotropy and inhomogeneity 17,43,45 ), and loading (larger IOP insult and cerebrospinal fluid pressure 57,[60][61][62][63].…”