AIM: To investigate the refractive and the histological changes in guinea pig eyes after posterior scleral reinforcement with scleral allografts. METHODS: Four-week-old guinea pigs were implanted with scleral allografts, and the changes of refraction, corneal curvature and axis length were monitored for 51d. The effects of methylprednisolone (MPS) on refraction parameters were also evaluated. And the microstructure and ultra-microstructure of eyes were observed on the 9d and 51d after operation. Repeated-measures analysis of variance and one-way analysis of variance were used. RESULTS: The refraction outcome of the implanted eye decreased after operation, and the refraction change of the 3 mm scleral allografts group was significantly different with control group (P=0.005) and the sham surgical group (P=0.004). After the application of MPS solution, the reduction of refraction outcome was statistically suppressed (P=0.008). The inflammatory encapsulation appeared 9d after surgery. On 51d after operation, the loose implanted materials were absorbed, while the adherent implanted materials with MPS group were still tightly attached to the recipient’s eyeball. CONCLUSION: After implantation of scleral allografts, the refraction of guinea pig eyes fluctuated from a decrease to an increase. The outcome of the scleral allografts is affected by implantation methods and the inflammatory response. Stability of the material can be improved by MPS.