Noninvasive Assessment of Ocular Structure in the Elderly 13-Lined Ground Squirrel.

The 13-lined ground squirrel (13-LGS) is an attractive model for vision research due to its cone-dominance, accessibility, and amenability to noninvasive retinal imaging. The ability to interpret results from longitudinal studies in this animal model is limited by a lack of normative data from aged animals. To address this, we used noninvasive imaging to characterize structural changes in the anterior segment and retina in 20 13-LGS aged 5-8 years of age. Our imaging revealed multiple age-related changes in the 13-LGS eye. Phenotypes include lens opacifications, loss of normal cone structure surrounding the optic nerve head, abnormal near-infrared reflectance and short-wavelength fundus autofluorescence signal, altered and disrupted retinal lamination, choroidal thinning, and cone mosaic disruptions and reflectivity alterations. While these qualitative observations were considered abnormal, quantitative measures of retinal thickness and cone density in elderly eyes were comparable to those of young controls. Age-related changes in ocular media and retinal structure in the 13-LGS need to be considered in future longitudinal studies.