Abstract: Objective  To observe the changes of the refractive state and axial length induced by two different hyperopic defocus methods in the infant guinea pigs; to discuss the sensitivity of guinea pigs to these two methods. Design Experimental study. Participants 18 male pigmented guinea pigs (age of 6 weeks). Method 18 pigmented guinea pigs (age of 6 weeks) were randomly assigned to 3 groups: normal control group (group A, 3 cases), Goggle myopia induction group (group B, 10 cases), aphakia induction group (group C, 5 cases). In the latter two groups, right eyes were used to be performed by the corresponding induced method, while left eyes were the control eyes. Refraction and axial lengths were examed before experiment and three weeks after induction. Compared the refractive developmental differences in the experimental eyes with the control eyes before and after the experiment, and comprehensively assessed the effectiveness of different methods of induction. Main Outcome Measures Axial lengths and refractive states. Results Before the inducement, the refrection and axial length were no significantly different among the three groups (P>0.05). Three weeks later, in comparison to the control eyes，the right eyes of group B and group C became more myopic (on average -2.83±0.80 D and-5.50±0.58 D, respectively) and elongated (on average 1.18±0.22 mm and 1.98±0.14 mm, respectively) (all P<0.05). Conclusions Aphakia and negative lens can interfere vision development and induce the myopic development  and axial growth in the infant guinea pigs.

Key words:  hyperopic defocus, aphakia; , axial length, myopic shift, animal, laboratory