AIM:To evaluate the dynamic ocular biometric changes of a modified form-deprivation myopia model in young guinea pigs.METHODS:The animals were randomly assigned to two groups:the monocularly deprived facemask group(MDF,with all the right eyes covered,n =24) and the normal control group(free of facemask,n =24).Each group was then equally divided into four subgroups which were followed up for 2,4,6 and 8 weeks,respectively.Parameters measured from every eye included refraction,corneal curvature,axial length and the dry weight of sclera at the posterior pole.RESULTS:All the facemasks remained in place during the follow-up.The covered eyes developed myopia with the vitreous chamber lengthening and the dry weight of posterior sclera reduced at each time point compared with the contralateral uncovered(P <0.05 at all time points).The changes had a linear correlation with the deprivation time(P <0.05).There were no significant differences in all the parameters between the uncovered eyes of MDF group and the normal control group(P >0.05 at all time points).CONCLUSION:Monocular form deprivation with the facemask is highly effective and non-invasive in inducing axial myopia in guinea pigs.The axial myopia is mainly caused by the increased vitreous chamber length and the weakened posterior sclera rigidity.The form-deprivation eye didn’t interfere with the natural development of the contralateral eye. AIM: To evaluate the dynamic ocular biometric changes of a modified form-deprivation myopia model in young guinea pigs. METHODS: The animals were randomly assigned to two groups: the monocularly deprived facemask group (MDF, with all the right eyes covered, n = 24) and the normal control group (free of facemask, n = 24) .Each group was then equally divided into four subgroups which were followed up for 2, 4, 6 and 8 weeks, respectively.Parameters measured from every eye included refraction, corneal curvature, axial length and the dry weight of sclera at the posterior pole .RESULTS: All the facemasks remained in place during the follow-up. The covered eyes developed myopia with the vitreous chamber lengthening and the dry weight of posterior sclera reduced at each Time points compared with the contralateral uncovered (P <0.05 at all time points). Changes had a linear correlation with the deprivation time (P <0.05). There were no significant differences in all the parameters between the uncovered eyes of MDF group and the normal control group (P> 0.05 at all time points). CONCLUSION: Monocular form deprivation with the facemask is highly effective and non-invasive in inducing axial myopia in guinea pigs.The axial myopia is mainly caused by the increased vitreous chamber length and the weakened posterior sclera rigidity.The form-deprivation eye did not interfere with the natural development of the contralateral eye.