Biomechanics of keratoconus: Two numerical studies

Area of Science:

• Ophthalmology
• Biomechanical Engineering
• Computational Biology

Background:

• Keratoconus, a condition causing steep corneas and vision impairment, has an unclear origin.
• Early corneal injury weakening stromal architecture is a suspected factor in keratoconus development.

Purpose of the Study:

• To investigate the biomechanical mechanisms underlying keratoconus.
• To explore how alterations in corneal stromal mechanics influence corneal shape and stress distribution.

Main Methods:

• A finite-element model of the five corneal layers was developed, incorporating heterogeneous mechanical properties of stromal ground substance and collagen fibers.
• Simulations assessed the impact of regional stromal softening and collagen fiber disorganization on corneal displacement and stress under intraocular pressure.
• The model was also used to simulate eye-rubbing-like loading to identify stress-prone corneal layers.

Main Results:

• Conical deformation and thinning occurred with mid-posterior stromal softening or collagen fiber dispersion.
• Softening anterior layers or the entire cornea did not induce conical deformation.
• Eye rubbing primarily stressed the deep posterior stroma, while other layers were minimally affected.

Conclusions:

• Mechanical instability or damage in the mid-posterior stroma may initiate keratoconus by stressing anterior corneal layers.
• This finding aligns with videokeratoscopy observations of posterior, but not anterior, elevation in early-stage keratoconus.