Corneal elasticity after oxygen enriched high intensity corneal cross linking assessed using atomic force microscopy

Area of Science:

• Ophthalmology
• Biomaterials Science
• Corneal Biomechanics

Background:

• Corneal cross linking (CXL) is a procedure to stiffen the cornea.
• High intensity (HI) CXL protocols aim to shorten treatment time.
• The effect of HI-CXL, with and without oxygen enrichment, on corneal elasticity is not fully understood.

Purpose of the Study:

• To assess and compare corneal stromal elasticity after conventional CXL, HI-CXL, and oxygen-enriched HI-CXL.
• To quantify changes in anterior and mid corneal stroma elasticity using Atomic Force Microscopy (AFM).

Main Methods:

• Human cadaver eyes were divided into four groups: control, conventional CXL, HI-CXL, and oxygen-enriched HI-CXL.
• Corneal epithelial debridement and riboflavin pretreatment were followed by specific ultraviolet light exposure durations and intensities.
• Atomic Force Microscopy (AFM) with micro-indentation was used to measure Young's modulus, quantifying stromal elasticity.

Main Results:

• Conventional CXL significantly increased anterior and mid stromal elasticity compared to controls.
• HI-CXL, with or without oxygen, did not significantly alter anterior stromal elasticity compared to controls.
• Both HI-CXL protocols resulted in significantly lower corneal stiffness compared to conventional CXL in the mid stromal region.

Conclusions:

• Conventional CXL significantly increases corneal stiffness more than HI-CXL protocols.
• Oxygen enrichment does not appear to significantly alter corneal elasticity changes induced by HI-CXL.
• HI-CXL, even with oxygen, may offer a less stiffening alternative to conventional CXL, particularly in the mid stroma.