Incidences and Range of Spontaneous Lesions in the Eye of Crl:CD-1(ICR)BR Mice Used in Toxicity Studies

The incidence and range of spontaneous pathology findings were determined in the eyes of male and female control Crl:CD-1(ICR)BR mice. Data were collected from 250, 430, 510, and 2,266 mice from control dose groups of 4-, 13-, 80- and 104-week studies, respectively, carried out between 2005 and 2013. Lesions of the eye were very rare in 4- and 13-week studies, uncommon in 80-week studies, and were of relatively higher incidence in 104-week studies. No sex predilection in the incidence of eye lesions was apparent. No neoplastic lesions were observed, and congenital lesions were very rare. The most common findings were cataracts, retinal degeneration, mineral deposits in the iris, keratitis, anterior uveitis, and mineral deposits in the corneal stroma. These lesions were observed only in animals from 80- and 104-week studies, except retinal degeneration which was observed in animals from all age-groups. There are no previous reports of mineral deposits in the iris in this strain of mice. It is hoped that reference to the incidences reported here will facilitate the differentiation of spontaneous lesions from compound-induced lesions in toxicology studies in this strain of mouse.