Abstract
Purpose: :
To develop a theoretical model for the photochemical kinetic mechanisms of corneal cross-linking with riboflavin.
Methods: :
Theoretical modeling and computer analysis of the photochemical kinetics of corneal cross-linking with riboflavin was developed, for combined type I and II mechanisms, using kinetic and rate constants derived from literature review of riboflavin kinetics and photochemistry. Model was constructed in Matlab, incorporating diffusion rates of O2 and riboflavin within corneal tissue, UVA energy distribution within tissue, and reaction kinetics of Type I and II pathways. Model output predicts relative concentration of oxygen in corneal tissue at various depths.
Results: :
The model predicts that oxygen is rapidly depleted during the first few seconds following UVA light exposure during corneal cross-linking with riboflavin, consistent with Type II mechanism. O2 is completely depleted for the next 10-15 minutes which suggests a predominance of Type I photochemistry. The model predicts combined Type I/II after 10-15 minutes as O2 begins to replenish itself as a function of depth.
Conclusions: :
A theoretical model for the photochemical kinetic mechanisms of corneal cross-linking with riboflavin has been developed. The results of this model suggest that the Type I photochemical mechanism where direct interaction between riboflavin triplets and corneal proteins lead to corneal cross-linking is the predominant effect of corneal cross-linking with riboflavin. The role of singlet oxygen and the Type II photochemical mechanism appears to produce a more minor effect.
Keywords: photodynamic therapy • cornea: basic science • computational modeling