Cataract and other ophthalmic lesions in senescence accelerated mouse (SAM). Morphology and incidence of senescence associated ophthalmic changes in mice.

In a murine model of accelerated senescence (SAM), grading score and incidence in cataract, periophthalmic lesions, opacity and ulcer of the cornea were determined in mice from 4 to 24 months of age. From 4 to 6 months of age, incidence and grading score of these four categories began to increase in both the accelerated senescence prone (SAM) and resistant series with normal aging, and these increases continued with aging. As compared with the resistant series, there was a higher incidence and grading score of the four categories and a higher rate of increase in the prone series. The prone 3 series in particular showed a much higher incidence and grading score on cataract, the rate being 27.5% and 70.6% at 12 and 16 months, respectively. Histologically, the cataract was classified into two types. In one, degeneration of lens fibers, disintegration of lens cortex, and at an advanced stage, liquefaction of the lens cortex and proliferation of the anterior lens epithelial cells occurred. In the other type, lens fibers lost their distinct shapes and a homogenous mass formed at the anterior and posterior superficial cortex. The anterior lens epithelial cells had shrunk. There was an opacity and ulcer of the cornea with keratitis and the corneal epithelium was lost in case of the latter. Periophthalmic lesions included catarrhal changes of the skin of the eyelids and face and blepharitis. There were no lesions specific to each of the prone and resistant series. Thus, SAM should prove to be a suitable murine model for investigation of age-related ophthalmic lesions, including cataract in humans.