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

PURPOSE: 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.
METHODS: 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.
RESULTS: 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.
CONCLUSION: 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.