Abstract
Purpose:
To characterize the responses of guinea pigs sourced from different breeding colonies to myopia-inducing stimuli using negative lens and form deprivation paradigms.
Methods:
English Short Hair guinea pig breeders were obtained from a commercial vendor (Elm Hill Labs, Chelmsford, MA - designated “Elm Hill” guinea pigs) and from a University-based breeding colony (University of Auckland, NZ - designated “NZ” guinea pigs). Elm Hill guinea pig pups were fitted with either negative lenses (-10, -5, or 0 D) or diffusers at 10 days of age. NZ guinea pigs were fitted with diffusers at 7 days of age. Both sets of animals were treated for 4 weeks. Ocular axial lengths were measured twice a week using high frequency A-scan ultrasonography, cycloplegic refractions were measured on treatment days 0, 14, and 28, and behavioral visual acuity measured on treatment day 28.
Results:
Elm Hill guinea pigs fitted with lenses exhibited minimal interocular differences in axial length and refractive error after 28 days of treatment; likewise, form deprivation (FD) failed to significantly affect the rate of ocular elongation or to induce a myopic shift in refractive error. Overall changes in interocular difference in axial length (treated minus control) were 0.03±0.1 mm for -10 D lenses, -0.20±0.43 mm for -5D lenses, -0.01±0.21 mm for 0 D lenses, and 0.07±0.16 mm for FD. Conversely, the NZ guinea pigs exhibited a 0.17±0.12 mm increase in interocular differences in axial length after 28 days of FD treatment.
Conclusions:
A systematic study of the ocular growth responses of young guinea pigs to myopia-inducing stimuli revealed significant strain-related differences. These results point to genetically determined differences in the sensitivity of emmetropization mechanisms to visual manipulation, even within the same breed. Finally, this works suggests that research groups wishing to work with a guinea pig myopia model should carefully consider the source of their animals.