ObjectiveTo investigate the changes of ocular biometric parameters during the recovery from form-deprivation myopia in guinea pigs. Methods Thirty guinea pigs, aged 2[KG-*2]-[KG-*9]3 weeks, were randomly divided into 2 groups:experimental group (n=20) and normal control group (n=10). The right eyes of guinea pigs in the experimental group were form-deprived with semi-transparent membranes for 4 weeks and subsequently allowed unrestricted vision for 3 weeks. The left eyes remained untreated as contralateral control eyes. The guinea pigs in the normal control group were raised with both eyes open for 7 weeks. Ocular biometric parameters of the guinea pigs were measured before and 4 weeks after form-deprivation, and 2,6, 0,4, and 21 days after re-exposure. Refraction was measured by retinoscopy after cycloplegia. Axial length, anterior chamber depth and lens thickness were measured by A-scan ultrasound, and the vitreous chamber depth was calculated. ResultsAfter 4 weeks of treatment, the right eyes of guinea pigs in the experimental group had myopic shift with refraction of (-2.88±2.30) D, and induced a relative myopia (-5.50±1.9) D. After re-exposure, the right eyes of guinea pigs in the experimental group experienced re-normalization, and the refraction was rapidly recovered in the initial 6 days. The refractive difference was (-0.18±0.26) D, vitreous chamber depth difference was (0.012 5±0.045 8) mm, and axial length difference was (0.018 3±0.035 9) mm between both eyes at 14 days after re-exposure, and were statistically non-significant (t=-2.049,P=0.080; t=0.610,P=0.575; t=1.443,P=0.192). Compared with the right eyes of guinea pigs in the normal control group, the refractive difference (-0.48±0.36) D was non-significant (t=-1.325,P=0.206) at 6 days after re-exposure, while the vitreous chamber depth difference was (0.0961±0.0630) mm and the axial length difference was (0.062 1±0.038 6) mm, statistically non-significant(t=1.652,P=0.14；t=1.607,P=0.125)at 2 days after re-exposure. ConclusionsGuinea pigs aged from 2 to 3 weeks with form-deprivation can experience re-normalization after re-exposure, along with a shortening of the vitreous chamber depth and axial length. The main recovery stage of ocular biometric parameters is in the initial 6 days after re-exposure.