Abstract
Purpose: :
Retinal mechanisms are likely involved in the development of form deprivation myopia (FDM). In order to determine the role of photoreceptors in FDM, we tested two mouse models of retinal degeneration with fast (Pde6brd1) and moderate (Pde6brd10) rates of degeneration. Both strains have a mutation in beta-PDE. Since loss of photoreceptors could affect ON pathway stimulation, dopamine levels were also assessed.
Methods: :
C57BL/6J (WT), Pde6brd1 (rd1) and Pde6brd10 (rd10) mice were goggled with a custom head-mounted goggling apparatus at 28 days of age. Following two weeks of goggling, mice were refracted with an automated infrared photorefractor. The difference between the goggled and opposite eye was calculated as the myopic shift. Mice were then sacrificed and retinas taken for dopamine and DOPAC analysis using HPLC.
Results: :
In contrast to goggled WT mice, goggled rd1 and rd10 mice both exhibited a significant myopic shift following two weeks of treatment (rd1: 5.37 +/- 0.74 D (SEM; p<0.001); rd10: 6.13 +/- 1.57 (SEM; p<0.001)). In comparison to WT mice, rd1 DA and DOPAC levels were significantly reduced (1.5 and 2.6-fold decrease, respectively). Rd10 mice, however, exhibited DA levels similar to WT, but reduced levels of DOPAC relative to WT animals. After goggling, DA and DOPAC levels in all three strains of mice were not significantly different between goggled and contralateral control eyes. However, there was a trend for lower levels of DA in goggled rd10 eyes compared to contralateral controls.
Conclusions: :
As expected, WT mice did not exhibit a shift in refractive error following form deprivation after two weeks of goggling, and correspondingly there were no differences in DA or DOPAC between goggled and contralateral control eyes. Interestingly, both the rd1 and rd10 mice, with few or less than normal photoreceptors, had increased susceptibility to goggling. Further research is needed to determine the relationship between refractive shifts and dopamine in these strains.
Keywords: myopia • retinal degenerations: hereditary • dopamine