Measuring Deformation in the Mouse Optic Nerve Head and Peripapillary Sclera

Area of Science:

• Ophthalmology
• Biomechanics
• Neuroscience

Background:

• The optic nerve head (ONH) and peripapillary sclera (PPS) are crucial for vision and susceptible to damage from elevated intraocular pressure (IOP).
• Understanding the biomechanical response of the ONH and its astrocytic structures to IOP changes is vital for diagnosing and treating conditions like glaucoma.

Purpose of the Study:

• To establish an ex vivo explant system utilizing multiphoton microscopy and digital volume correlation.
• To quantify the full-field deformation of the peripapillary sclera (PPS) and optic nerve head (ONH) astrocytic structure in response to intraocular pressure (IOP) variations.

Main Methods:

• Mouse eyes (GLT1/GFP) were explanted and subjected to controlled inflation for imaging.
• Regional strains and changes in astrocytic lamina and PPS shape were analyzed using laser-scanning microscopy.
• Astrocyte volume fraction and GFAP labeling were assessed for comparison.

Main Results:

• The ONH astrocytic structure remained stable in explants over 3 hours.
• Global strain was significantly greater in the nasal-temporal direction compared to other directions.
• Chronic IOP elevation led to increased PPS area, reduced perimeter elongation, and altered astrocyte orientation.

Conclusions:

• The explant inflation test effectively measures the strain response of the mouse ONH to applied IOP.
• Initial findings reveal distinct regional biomechanical responses within the ONH to both acute and chronic IOP elevation.