Long-term biomechanical properties after collagen crosslinking of sclera using glyceraldehyde

Chemical crosslinking by glyceraldehyde has been shown to increase significantly the biomechanical rigidity of sclera. It might therefore become an option for a sclera-based treatment of progressive myopia. The present pilot study was designed to test the long-term biomechanical efficiency of the new crosslinking method.

Six Chinchilla rabbits were treated with sequential sub-Tenon's injections of 0.15 ml 0.5 m glyceraldehyde, which were given in the supero-nasal quadrant of the right eye (OD) five times over 14 days. The rabbits were killed 4 months and 8 months after crosslinking treatment, respectively. Biomechanical stress-strain measurements of scleral strips from the treatment area were performed and compared to non-treated contralateral control sclera using a microcomputer-controlled biomaterial testing device. In addition, the eyes were examined histologically by light microscopy to evaluate possible side-effects.

Following the crosslinking treatment, the ultimate stress was 10.2 +/- 2.3 MPa after 4 months and 8.5 +/- 2.2 MPa after 8 months versus 2.4 +/- 0.3 MPa in the controls (increases of 325% and 254.17%, respectively); Young's modulus was 104.6 +/- 13.7 MPa after 4 months and 53.2 +/- 5.2 MPa after 8 months versus 9.6 +/- 1.3 MPa in the controls (increases of 989.6% and 554.17%, respectively); and ultimate strain was 15.8 +/- 1.5% after 4 months and 24.1 +/- 0.7% after 8 months versus 38.4 +/- 4.6% in the controls (decreases of 58.84% and 37.24%, respectively). Histologically, no side-effects were found.

Our new method of scleral collagen crosslinking proved very efficient in increasing scleral biomechanical strength over a period of up to 8 months. Glyceraldehyde can be applied easily by sequential parabulbar injections. Before clinical application in myopic patients, a study in an animal myopia model is recommended.