Abstract:AIM: To explore the characteristic of relaxation of porcine cornea after LASIK. · METHODS: Usual LASIK was performed on fresh porcine corneas with stable intraoculer pressure(IOP) maintained through optic nerve irrigation . The ablation depth on stroma is 30%, 50% and 70% respectively. Then the dumbbell- shaped corneal strip specimens were cut and stored in 20% Human Albumin solution for use (4oC).Sip up the Albumin solution on specimens, and fixed them on homemade jig. Stress relaxation tests were performed on Tytron250 Dynamics Experiment System. The loading speed was 385mm/min，extending rate was 1.5, and relaxation time was 1 000s. The data were collected electronically and automatically. · RESULTS: In LASIK procedure, though a single flap-cutting can cause a little reduction of corneal stress relaxation (P < 0.05, P =0.49), the cornea may still remain its property of visco-elasticity. When ablation depth was 30% or more, corneal stress relaxation decreased to almost one half (P < 0.01).The change of corneal stress relaxation degree in vertical meridian specimen was lower than that in horizontal specimen, especially when ablation depth was 70%, and it's statistically significant（P <0.001）. In LASIK operation, the more depth the ablation, the more reduce the stress relaxation degree, and it’s easy to cause deformation and creep deformation. · CONCLUSION: The changes of the stress relaxation in vertical and longitudinal meridian specimens are similar, and slightly obvious in longitudinal specimen, especially in 70% ablation group.
