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S. B. Jabbar, A. E. Faulkner, G. F. Schmid, F. Schaeffel, J. Abey, P. M. Iuvone, M. T. Pardue; Rod Photoreceptor Contributions to Refractive Development and Form Deprivation Myopia in Mice. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1726.
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Visually guided emmetropization begins with detection of the visual environment by the retina. In this study, we examined the role of a specific subset of retinal neurons, the rod photoreceptors, in detecting visual input for emmetropization. Refractive development and the response to form deprivation myopia was evaluated in mice with a functional mutation in rod transducin-α (Gnat1 -/-).
Refractive development of Gnat1-/- mice was monitored from p28 to p140 (n=2-8/timepoint). The response to form deprivation was tested using a head-mounted diffuser goggle from p28 to p84 (n = 5 goggled, 6 control). Weekly refractions were obtained with automated infrared photoretinoscopy for all mice. Axial length was measured weekly with partial coherence interferometry from p28 to p84 under form deprived conditions. Dopamine and DOPAC analysis using HPLC was performed from retinas collected from separate mice at p7 (n=7), p14 (n=7), p28 (n=5), and p140 (n=8)for the development studies and at the final time point for the form deprived mice (n= 5 goggled, 5 control).
In contrast to wild-type C57BL/6 mice which shift towards more hyperopia and then plateau, refractive errors of Gnat1-/- mice did not change over the 16 weeks examined. Gnat1 -/- mice had an average refractive error of 7.74±1.04D (SD). Furthermore, Gnat1-/- mice had no response to form deprivation. There were no statistically significant differences between refractions (RM ANOVA p=0.604; goggled 7.57±0.59D, contralateral 7.81±0.58D) or axial length (RM ANOVA p=1.000; goggled 3.282±0.120mm, contralateral 3.281±0.120mm) in the goggled, contralateral, or control Gnat1-/- eyes. There were no statistically significant differences in dopamine and DOPAC levels in all treatment groups following 8 weeks of form deprivation (One way ANOVA DA: p=0.714, DOPAC: p=0.726).
Gnat1-/- mice did not exhibit a shift in refractive error with normal refractive development. There were no changes in refractive error or axial length following form deprivation. These results suggest that rod photoreceptors may be important for the detection of the visual signals that control emmetropization and myopic development.
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