A triphasic analysis of corneal swelling and hydration control

Area of Science:

• Ophthalmology
• Biophysics
• Biomaterials Science

Background:

• Corneal hydration is crucial for vision, regulated by active ion transport at the corneal endothelium.
• The precise mechanism linking endothelial ion transport to corneal thickness regulation remains unclear.
• Existing models do not fully elaborate on how ion transport influences stromal swelling pressure.

Purpose of the Study:

• To develop a detailed model of corneal hydration control.
• To elucidate the mechanism by which endothelial ion transport regulates corneal stromal thickness.
• To provide a theoretical basis for corneal imbibition and swelling pressures.

Main Methods:

• Modeling the corneal stroma as a triphasic material under steady-state conditions.
• Developing an ion flux boundary condition to represent active endothelial transport.
• Solving governing equations in cylindrical and spherical coordinates for different corneal geometries.

Main Results:

• The model demonstrates a mechanism for active ion transport regulating corneal hydration.
• It explains the origins of imbibition pressure and stromal swelling pressure.
• The model integrates the Donnan equilibrium and the pump-leak hypothesis for corneal swelling.

Conclusions:

• Active ion transport at the corneal endothelium is a key regulator of corneal hydration and thickness.
• The developed model offers a mechanistic explanation for corneal swelling pressures.
• This work provides a unified framework for understanding corneal hydration dynamics.