To evaluate the change of corneal collagen after riboflavin-ultraviolet-A induced corneal collagen cross-linking (CXL) on rabbit eyes, and investigate the role of collagen fiber remodeling in biomechanical stability after CXL.

CXL was performed on the right eye of 15 healthy New Zealand rabbits, and all the left eyes were used as normal controls. Five eyes were randomly chosen at 1 day, 7 days, and 4 weeks post CXL to determine the effect. Picrosirius-polarization and stress-strain tests were performed on corneal specimens to analyze the quantitative change of collagens, peak load, peak stress, and elastic modulus.

The normal corneal collagen fibrils were regularly arranged with a parallel lamellae structure. The predominant collagen type in the normal corneal stroma was collagen Ⅰ, and collagen Ⅲ was dispersed within collagen Ⅰ. By day 7, the amount of type Ⅲ collagen increased and the fiber diameter became thick and asymmetric. By week 4, the amount of type Ⅲ collagen still increased and was intermingled with type Ⅰ collagen in the stroma. During the observed period, the corneal elastic modulus, peak load, and peak stress increased significantly compared with the normal cornea. By day 1, the elastic modulus, peak load, and peak stress reached the highest point and then gradually went down, but still increased significantly than normal controls (P＜0.05).

The ratio of type Ⅲ/Ⅰ collagen and their distribution are significantly changed after CXL, which indicates that collagen fiber remodeling occurs and long-term biomechanical stability may be concerned with this remodeling.