Animal models of cataracts provide essential tools for investigating the pathological mechanisms and evaluating pharmacological interventions. The precision of lens-opacity grading is contingent upon the congruence between anatomical characteristics and the grading system used. Current clinical grading frameworks are primarily based on human ocular anatomy; however, there are notable anatomical disparities among animal species. For instance, the lens diameter in mice is approximately (1. 2 ± 0. 1) mm, compared with (8. 5 ~ 9. 5) mm in humans, with mice having a relatively smaller nuclear region. Similarly, the corneal curvature in rabbits is (7. 2 ± 0. 1) mm compared with ( 8. 0 ± 0. 2 ) mm in humans, and the zebrafish lens lacks the conventional nucleus-cortex differentiation observed in mammals. These anatomical differences contribute to issues such as dimensional redundancy, detection bias, and grading distortion when applying human-based clinical grading systems to animal models. This review examines various method for inducing cataracts in animal models, systematically evaluates how the above anatomical variations affect the suitability of existing grading systems, and proposes tailored strategies to enhance grading accuracy. Specifically, we recommend employing a modified lens opacities classification system Ⅲ (LOCSⅢ) or a simplified grading approach for mice, developing a grading system focused on nuclear opacity for rabbits, and utilizing grayscale-quantification techniques for zebrafish. These customized method ologies aim to establish more precise grading standards to support cataract research utilizing animal models.