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Sauparnika Vijay, Annegret Dahlmann-Noor, Silke Becker, Hari Jayaram, Ashkan Khalili, G Astrid Limb, Peng T. Khaw; Changes in Electrophysiology & Retinal Ganglion Cell Number in a Magnetic Bead-injection Rat Model of Experimental Glaucoma. Invest. Ophthalmol. Vis. Sci. 2012;53(14):170.
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© ARVO (1962-2015); The Authors (2016-present)
To compare early and late functional changes in retinal ganglion cells in the recently described magnetic bead-injection model of experimental glaucoma in rats.
Three groups of anterior chamber (AC) injections in rat eyes: (1) paramagnetic microbeads, directed into the iridocorneal angle (ICA) using a ring magnet place around the eye (n=10), (2) paramagnetic beads distributed at random, no magnet (n=9), (3) controls: balanced salt solution (BSS) (n=8).Outcomes: (1) full field flash ERG, recorded in both eyes simultaneously: quantification of the amplitude of positive and negative scotopic threshold response (STR), a and b waves; (2) retinal wholemounts: retinal ganglion cells (RGC) count.Prism, GraphPad Software, Inc., was used to perform one-way analysis of variance. The different groups were compared by applying Bonferroni’s correction.
At seven days after the injections, the eyes with beads directed to the ICA had a significant reduction of the pSTR when compared to BSS injected eyes, p<0.0001. Eyes with randomly distributed beads also had a reduction in the pSTR when compared to BSS injected eyes, p=0.04. There was no significant difference in the amplitude of pSTR nor nSTR between random bead eyes and eyes with beads in the ICA. There was no significant reduction in the number of RGC across the different groups.Re-analysed based on IOP rise, pSTR amplitude in eyes with high IOP was significantly lower than in eyes with minimal IOP rise.At 28 days after injection, bead-injected eyes had a significant reduction of pSTR compared to BSS injected eyes, p<0.0001. RGC count in the bead-injected groups was significantly reduced compared to BSS injected eyes.
In the magnetic bead injection model of rat glaucoma, the IOP rise attenuates RGC function in the retina. Changes in electrophysiology precede changes in retinal ganglion cell number. Specific changes to RGC function might be restricted to the eyes with mild to moderate IOP rise.
Figure 1 At seven days after the injections, the pSTR of the eyes with beads directed to the iridocorneal angle with a magnet was significantly smaller than that of the BSS injected eyes .
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