Effects of Combining External Mechanical Load with UV-A Light/Riboflavin CXL onto Corneal Curvature

Abstract

Purpose : The effect of supplying a static mechanical load to the anterior corneal stroma during crosslinking (CXL) on refractive power and collagen structure of cornea is unclear. This study tested the hypothesis that external mechanical loading in combination with CXL results in the change of the corneal effective refractive power (Eff.RP) in ex vivo rabbit eyes.

Methods : A total of 12 pairs of fresh rabbit eyes were enucleated and their epitheliums removed. The intraocular pressure was kept at 20mm H₂O. One eye of each pair of the first group (n=6) and the second group (n=6) was treated with a typical UV-A light Riboflavin CXL procedure. In addition to CXL, a 1.6mm diameter central loading was applied to treated eyes such that 15% deformation, measured as change in the distance between the corneal apex and the optical nerve head, was achieved. The control eyes of Group1 were subjected to the identical mechanical load and riboflavin solution, but were not exposed to UV-A light. The control eyes of Group2 were crosslinked, but received no mechanical loading. Corneal topography and optical coherence tomography (OCT) were taken over a 12-hr period to collect Eff.RP and apical corneal thickness. Paired t-tests were used for statistical analysis.

Results : Combination of CXL and mechanical loading resulted in significant increase of Eff.RP, when compared against the non-crosslinked controls in Group1 (p=0.002), and non-loaded controls in Group2 (p=0.001). The change in the apical thickness of treated corneas and controls corneas is statistically significant in Group2 (p=0.002), but not in Group1 (p=0.593).

Conclusions : Our results support the hypothesis that a combination of external loading and CXL will result in the change of Eff.RP. Further investigation will focus on the influence of external mechanical load on changes in corneal thickness. In addition, modification in collagenous fibrillar structure during CXL with simultaneous loading and its effects on Eff.RP will be studied.

This is a 2020 Imaging in the Eye Conference abstract.

 

Figure 1. The average change in Eff.RP between the initial and final data points over span of 12hrs; all treated eyes were crosslinked and subject to mechanical loading whereas control eyes in Group1 (n=6) were exposed to loading only; control eyes in Group2 (n=6) were crosslinked only.

 

Figure 2. The average change of apical cornea thickness over 12hrs; experimental conditions for Group1 and 2 were the same as in Figure 1.