Ocular Pressure-Volume Relationship and Ganglion Cell Death in Glaucoma

Area of Science:

• Ophthalmology and Vision Science
• Biomechanical Engineering
• Cell Biology

Background:

• Glaucoma is a leading cause of irreversible blindness.
• Ganglion cell (GC) death is a hallmark of glaucoma, often associated with elevated intraocular pressure (IOP).
• However, the relationship between ocular biomechanics, volume, and GC loss, particularly in normal-tension glaucoma, requires further elucidation.

Purpose of the Study:

• To investigate the correlation between ocular biomechanical properties (volume, elasticity) and ganglion cell death in glaucoma.
• To explore the ocular volume-pressure relationship and its implications for glaucoma pathogenesis.
• To evaluate the DBA/2J mouse model for normal-tension glaucoma.

Main Methods:

• Studied glaucomatous DBA/2J mice and wild-type controls, assessing ganglion cell population via confocal microscopy.
• Analyzed ocular volume (V_S) and elasticity (volumetric K_S, tensile E_S) in mice and human patient data.
• Developed mathematical models for the ocular volume-pressure relationship.

Main Results:

• Glaucomatous DBA/2J mice showed significant ganglion cell loss, reduced ocular elasticity (K_S, E_S), and increased ocular volume (V_S), even with normal IOP.
• Ganglion cell population negatively correlated with V_S, age, and IOP in D2 mice.
• Reduced ocular elasticity (K_S, E_S) was observed in both glaucomatous mice and human patients with prolonged ocular expansion.

Conclusions:

• Disturbances in ocular volume-pressure homeostasis, characterized by low elasticity and increased volume, are linked to ganglion cell death in glaucoma.
• The DBA/2J mouse model with normal IOP and GC loss is suitable for studying normal-tension glaucoma.
• Ocular biomechanics play a critical role in glaucoma pathogenesis, extending beyond elevated IOP.