Depth-dependent changes in collagen organization in the human peripapillary sclera

Area of Science:

• Ophthalmology and Vision Science
• Biomechanical Engineering
• Connective Tissue Biology

Background:

• The collagenous structure of the human peripapillary sclera is crucial for optic nerve head (ONH) biomechanics.
• Understanding scleral collagen is vital for glaucoma research, a condition affecting the ONH.
• Previous studies have not fully detailed the depth-dependent collagen architecture of the peripapillary sclera.

Purpose of the Study:

• To map the anisotropic collagen structure of the normal human peripapillary sclera.
• To investigate collagen fibril orientation and alignment as a function of tissue depth.

Main Methods:

• Wide-angle x-ray scattering (WAXS) was employed to analyze collagen.
• Collagen fibril orientation was quantified across serial sections of the peripapillary sclera.
• Two parameters were measured: preferential fibril alignment and the degree of collagen alignment (anisotropy).

Main Results:

• The inner sclera (one-third) showed randomly or radially aligned collagen fibrils relative to the ONH.
• The outer sclera (two-thirds) exhibited a circumferential collagen arrangement encircling the ONH.
• Collagen anisotropy peaked in the mid-stroma and decreased towards the scleral surfaces, with regional variations observed.

Conclusions:

• The human peripapillary sclera displays significant, depth-dependent, and region-specific collagen structural variations.
• Circumferential collagen in the outer sclera may provide mechanical support to the lamina cribrosa insertion.
• These findings enhance our understanding of ONH biomechanics and glaucoma pathogenesis.