Corneal Collagen Ordering After In Vivo Rose Bengal and Riboflavin Cross-Linking

Area of Science:

• Ophthalmology
• Biomedical Engineering
• Materials Science

Background:

• Corneal collagen cross-linking (CXL) enhances corneal stiffness by forming covalent bonds between stromal proteins.
• CXL effectiveness may vary with depth due to photoinitiator diffusion, potentially impacting collagen organization.
• Second harmonic generation (SHG) microscopy is a valuable tool for visualizing collagen structure.

Purpose of the Study:

• To investigate depth-dependent changes in stromal collagen organization after in vivo corneal CXL.
• To compare collagen organization following riboflavin/UV (UVX) and Rose Bengal/green light (RGX) CXL treatments.
• To assess the temporal changes in collagen organization at 1 and 2 months post-CXL.

Main Methods:

• Rabbit corneas underwent in vivo CXL using either UVX or RGX.
• Collagen fiber organization was imaged using SHG microscopy at varying depths.
• The order coefficient (OC) and total SHG signal were quantified to assess collagen organization.

Main Results:

• CXL-treated corneas showed significantly increased OC compared to untreated corneas at both 1 and 2 months.
• RGX treatment resulted in slightly higher OC values than UVX treatment.
• Increased SHG signal, indicating more organized collagen, was observed in CXL corneas post-surgery.

Conclusions:

• Enhanced collagen organization, measured by OC, correlates with increased corneal stiffness after CXL.
• Collagen organization changes detected by SHG microscopy extend deeper into the stroma than anticipated.
• These findings suggest a more widespread structural remodeling of the cornea following CXL than previously recognized.