Understanding Species Variation In The Occurrence Of Spontaneous Background Eye Lesions In Toxicology Studies: A Comparative Study

By Nirmala Chinnappareddy, Amanda Hunerdosse, Julie Forget, Simone Iwabe, and Norbert Makori

Findings By Species

Rats: Among 930 rats (465 males, 465 females) examined, 19.57% had background ocular findings. The most common lesions included cataracts (67.58%), corneal dystrophy (30.22%), and other findings (2.20%). Prevalence was comparable between males (19.35%) and females (19.78%).

Mice: Of 690 mice (346 males, 344 females) examined, 11.01% presented with background ocular lesions. Cataracts were the most frequently observed (78.95%), followed by retinopathy (11.84%), corneal dystrophy (5.26%), and other findings (3.95%). The prevalence was similar between males (11.27%) and females (10.76%).

Non-Human Primates (NHPs): A total of 599 NHPs (300 males, 299 females) were assessed, with 8.01% exhibiting background ocular lesions. These included cataracts (56.25%), bilateral optic atrophy (12.50%), optic disc variants (10.42%), retinopathy (2.08%), and other findings (10.42%). Males showed a higher prevalence (13.65%) compared to females (5.62%).

Dogs: Among 162 dogs (81 males, 81 females), 9.26% had background ocular findings. Cataracts were the most common (53.33%), followed by corneal dystrophy (13.33%), retinopathy (12.5%), and other findings (20.00%). Prevalence rates were comparable between males (9.88%) and females (8.64%).

Recommendations

To minimize variability and ensure study integrity, animals with pre-existing ocular findings should either be assigned to control groups or excluded from the study based on the severity of the lesions. Proper screening and allocation strategies are essential to maintaining data reliability in nonclinical ocular toxicity assessments.