Abstract
Purpose::
As high relative sodium (Na+) and chloride (Cl-) and Potassium (K+) abundance exists in the retina and choroid of the myopic chick eye immediately after form deprivation (FD) (Liang et al 2004, Crewther et al 2006), and myopia due to negative lenses leads to similar morphological changes as FD (Beresford et al 2000) we predicted that refractive compensation to optical defocus should also lead to significant changes in Na+, Cl- and K+ abundance across the retina. We tested this hypothesis using X-Ray microanalysis (XREM) in chicks after 72 hours of positive and negative lens optical defocus and correlated this with concurrent changes in AQP4 and Kir4.1 channel expression.
Methods::
Sixty-nine chickens were raised from 5 days post-hatching for 72 hours wearing monocular spectacle lenses of +/-10D or no lenses. Immediately after sacrifice, retinae were prepared for elemental microanalysis and immunohistochemistry with anti-AQP4 and anti-Kir4.1 antibodies.
Results::
Comparison of the ratios of Na, Cl and K ion concentration of the lens wearing eyes to the fellow eyes showed a sign dependent differential pattern of abundance across the retina, especially in the outer retina and nerve fibre layer. The pattern of AQP4 and Kir4.1 expression was also associated with abundances of Na+ and Cl- across the retina.
Conclusions::
Induction of refractive compensation to optical defocus is associated with changes in the concentrations of sodium, chloride and potassium across the retina and in expression of AQP4 and Kir4.1.
Keywords: myopia • ion channels • Muller cells