Thin Lamina Cribrosa Beams Have Different Collagen Microstructure Than Thick Beams

Area of Science:

• Ophthalmology
• Biomechanics
• Histology

Background:

• The lamina cribrosa (LC) is a crucial structure in the optic nerve head, influencing intraocular pressure (IOP) regulation.
• Understanding the microstructural properties of LC beams is essential for comprehending optic nerve head biomechanics and glaucoma pathogenesis.

Purpose of the Study:

• To investigate and compare the collagen microstructural crimp characteristics of thin and thick lamina cribrosa (LC) beams.
• To determine the relationship between LC beam width and its collagen fiber crimp properties.

Main Methods:

• Sheep eyes were fixed, and cryosections of the LC were analyzed using polarized light microscopy.
• Collagen fiber microstructure, including crimp waviness, tortuosity, and amplitude, was measured for individual LC beams.
• Linear mixed effects models were employed to assess associations between LC beam width and crimp characteristics.

Main Results:

• LC beam width was significantly associated with crimp waviness (positive), tortuosity (positive), and amplitude (negative).
• Thin beams (average width 13.11 μm) exhibited lower waviness and tortuosity but higher amplitude compared to thick beams (average width 26.10 μm).
• Specifically, thin beams had average waviness of 0.27 rad, tortuosity of 1.017, and amplitude of 1.88 μm, versus thick beams with 0.33 rad, 1.025, and 1.58 μm, respectively.

Conclusions:

• The study reveals heterogeneity in the mechanical properties of LC beams based on their width.
• Thin LC beams, being less wavy, may stiffen earlier under IOP, potentially offering similar axonal support to thicker beams.
• Further in-situ mechanical testing is recommended to validate these findings and their implications for axonal protection.