A cellular solid model of the lamina cribrosa: mechanical dependence on morphology

Area of Science:

• Ophthalmology
• Biomechanics
• Medical Imaging

Background:

• Primary open-angle glaucoma causes vision loss through optic nerve head (ONH) damage.
• Optic nerve head (ONH) biomechanics are implicated in glaucoma pathogenesis.
• Quantifying ONH stress and strain is vital for understanding glaucoma progression.

Purpose of the Study:

• To characterize physiological stress and strain levels in the optic nerve head (ONH).
• To investigate how ONH biomechanics are influenced by tissue properties, geometry, and microstructure.
• To model the relationship between scleral biomechanics and ONH microstructural response.

Main Methods:

• Developed an analytical microstructural model of ONH load-bearing tissues.
• Utilized an octagonal cellular solid model matching lamina cribrosa (LC) porosity and pore area.
• Applied a complex variable method for plane stress to link scleral loads to LC microstructure.

Main Results:

• Stress amplification in the LC ranged from 2.8 to 24.5 times intraocular pressure (IOP).
• Scleral properties (Young's modulus, thickness, canal eccentricity) were key determinants of LC strain.
• Elliptical canals induced greater strain than circular canals, with strains reaching 5% for an IOP increase from 15 to 50 mm Hg.

Conclusions:

• Optic nerve head (ONH) biomechanics, particularly stress and strain, are critical in primary open-angle glaucoma.
• Scleral geometry and material properties significantly influence ONH strain.
• Understanding these biomechanical factors can inform strategies to mitigate glaucoma-induced vision loss.