Figure 1. Anatomic structure of the eyeball

A: The human eye is 26.5 mm in length (slightly longer than normal) and its lens thickness is about 2.5 mm. B: The guinea pig eye is 9.2 mm in length and its lens thickness is 3.2 mm. C: The mouse eye is 2.7 mm in length and its lens thickness is 1.3 mm. The ratio of lens to ocular length in mouse is greater than those in human (about five-fold) and guinea pig (about 1.4 fold).