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Liqin Jiang, Sarah Kochik, Yang Shen, Christine Frances Wildsoet; Origin of different responses to myopia-inducing stimuli in two guinea pig strains. Invest. Ophthalmol. Vis. Sci. 2016;57(12):No Pagination Specified.
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© ARVO (1962-2015); The Authors (2016-present)
We previously reported two strains of guinea pigs to vary significantly in their sensitivity to myopia-inducing stimuli, including negative lenses and form deprivation (M Garcia et al. 2015 ARVO E-abstract 2167). To further explore the mechanism underlying this difference, this study focuses on the choroid, whose thickness is known to be modulated optical defocus stimuli.
For both guinea pig strains (EH & NZ), choroidal thickness was evaluated longitudinally in normal animals by posterior segment SD-OCT (Bioptigen), with data from left eyes reported here. Additional animals (NZ, n=3; EH, n=4; 10 months old), wore -5 and +5 D lenses over the right and left eyes respectively for 8 h, with choroidal thickness changes evaluated by A-scan ultrasongraphy.
The two strains of guinea pigs showed consistent differences in normal choroidal thickness, at both young and older ages (OCT data: 5.5 months, NZ vs EH: 118±11 vs 138±12 mm, p=0.02; 10 months, NZ vs EH: 110±11 vs 127±21 mm, p<0.05). Interestingly, the NZ animals appeared more sensitive to minus lenses, shown by choroidal thinning while the EH animals were more sensitive to plus lens-induced thickening (-5D treating: NZ vs. EH, -28±26 vs. -8±13 μm; +5D treating: NE vs. EH, -0.7±15 vs. 9±20 μm; ns.). Before the lens treatments, both strains showed minimal interocular difference in choroidal thickness (R vs. L: NZ, 108±9 vs. 102±7 μm; EH, 125±21 vs. 127±18 μm; ns.).
Together with the past observation of differences in the sensitivity of the two strains of guinea pigs to myopia-inducing stimuli, the naturally occurring difference of choroid thickness and differences in responsiveness of their choroids to optical defocus reported here raises the question of whether similar differences in humans might contribute to apparent differences in susceptibility to myopia.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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