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S.G. Crewther, M.J. Goodyear, D.P. Crewther; Optically Induced Refractive Errors Are Associated With Systematic Changes In Sodium, Chloride And Potassium Ions Across The Retina . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1802.
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The abundance of sodium (Na+), chloride (Cl–) and potassium (K+) ion is significantly higher in the retina and choroid of the eye of the myopic chick immediately after form deprivation (FD) (Liang et al 2004, Crewther IOVS 2005). Such elevated levels are dissipated during refractive recovery. Thus we predicted that refractive compensation to negative and positive optical defocus should also lead to significant changes in Na+, Cl– and K+ abundance in the retina and choroid. We tested this hypothesis using X–Ray elemental microanalysis (XREM) in chicks during the induction of myopia and hyperopia.
Twenty–four chickens were raised from 6 days post–hatching for up to 72 hours with monocular spectacle lenses of +/–10D. Immediately after sacrifice, pieces of central retina were frozen in liquid propane, freeze dried and prepared for scanning electron microscopy and XREM. Analyses were carried out on a JEOL scanning electron microscope equipped with an energy dispersive X–ray detector. Beam current was measured by means of a Faraday cup and all analyses were conducted at an accelerating voltage of 15 kV. A 20micron x 20 micron window was selected for the detection of x–rays and used for sequential scans across the retina from the retinal pigment epithelium to ganglion cell layer.
Comparison of the quantitiative analyses of concentrations of Na, Cl and K ion between the lens wearing and fellow eyes showed a variable pattern at 24 hours and a sign dependent differential distribution across the retina after 48 hours of lens wear.
Refractive compensation to optical defocus is associated with changes in the concentrations of sodium, chloride and potassium which seem to correlate with relative increases in retinal thickness, choroidal and vitreal volumes and changes in refractive error.
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