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A. E. Faulkner, N. Pozdeyev, P. M. Iuvone, M. T. Pardue; The Effect of Lens Defocus versus Form Deprivation on Refractive State and Dopamine in Nob Mice. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3846.
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© ARVO (1962-2015); The Authors (2016-present)
Nob mice have a mutation in nyx which results in defective retinal transmission along the ON pathway. Previous studies showed that nob mice have an increased susceptibility to form deprivation myopia compared to wild-type C57BL6 mice (Pardue et al., 2008). As expected with the absence of ON pathway stimulation, nob mice were also shown to have decreased dopamine release. Our current study seeks to compare myopia induced by diffuser goggles versus negative lenses in nob mice.
Nob mice were goggled at 28 days of age with diffusers (n = 10) or lenses (n=6). Diffusers were applied as previously described (Faulkner et al., 2007). Lenses consisted of (-)10 diopter (D) PMMA contact lenses, fitted in the same custom head-mounted goggling apparatus as the diffuser goggle. Mice were refracted at two weeks. The difference between the goggled and opposite eye was calculated as the myopic shift. Dopamine (DA) and DOPAC analyses were performed via HPLC on retinas extracted 48 hours after the final refraction.
Diffuser goggles induced a 3.89 +/- 0.21 D (SEM; p<0.001) shift following two weeks of form deprivation in nob mice. Similarly, negative lenses induced a myopic shift of 3.56 +/- 0.35 D (SEM; p<0.01). DA and DOPAC levels were not significantly different in nob mice wearing diffuser goggles (DOPAC: p=0.712; DA: p=0.483).
Form deprivation and lens-induced defocus elicited comparable myopic shifts in nob mice, suggesting a potential common mechanism. The lack of changes in DA and DOPAC in diffuser-goggled nob mice is likely due to the absence of ON-pathway transmission. If DA acts as a stop signal to excessive eye growth, then decreased stimulation of DA, as found in nob mice, may result in accelerated myopic eye growth with either form deprivation or lens defocus. Future experiments examining DA and DOPAC levels in lens-goggled nob mice will further confirm this hypothesis.
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