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F. Valiente-Soriano, M. Salinas-Navarro, M. Jiménez-López, A. Ortín-Martínez, L. Alarcón-Martínez, I. Cánovas, J. M. Bernal, M. Avilés-Trigueros, M. Vidal-Sanz; Effects of Elevated Intraocular Pressure on the Retinal Ganglion Cell Population in Adult Pigmented Mice. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5486.
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© ARVO (1962-2015); The Authors (2016-present)
To study the effects of elevated intraocular pressure on the survival of retinal ganglion cells (RGC).
In adult C57/BL6 mice (25-40g) the left eye received laser photocoagulation (532nm wavelength, 100mW power, 0.05 second duration, 100 µm diameter spot size) on limbar and episcleral veins. Intraocular pressure (IOP) in both eyes was measured with a TonoLab® prior to and at 24h, 48h and 72 hours and at 1, 2, 4, 6, or 8 wks after lasering. Mice were divided in groups I and II, and analyzed at 2 or 8 weeks, respectively. To identify the RGC population, 10% Hydroxistilbamidine methanesulfonate (Invitrogen, Molecular Probes, Eugene, Or) was applied over the surface of both superior colliculi one week prior to animal processing. Retinas were prepared as whole-mounts, examined and photographed under a fluorescence microscope (Axioscop 2 plus, Zeiss, Germany) equipped with a digital high-resolution camera and a motorized stage, connected to an image analysis system with an automatic frame-grabber device (Image-Pro Plus, ver. 184.108.40.206, IPP). Retinas were imaged by adjacent, non-overlapping frames captured in raster pattern. Each of these frames was counted with image analysis software IPP. And an isodensity contour plot was generated for each retina (SigmaPlot 2002 for Windows, ver 9.0).
Laser treatment induced an increase in mean intraocular pressure of approximately twice its baseline that was maintained during the first three days after lasering. In group I (n=11) basal IOP values were 16.1±0.8 (mean±SD), increased to 31.4±6.6 at 24 hours and decreased to basal values by three days. Similar values were observed in Group II (n=13), with basal IOP values of 15.5±1.7 that increased to 33.2 ±11.5 at 24 hours and decreased to basal values by three days. In group I, the mean RGC population in the lasered retinas (21,916±11,760) represented 55% of the values found in their contralateral control eyes (39,683±2,093). In group II the mean retinal ganglion cell population in the lasered retinas (15,496±10,343) represented 48% of the values found in their contralateral control eyes (35,009±2,903).
Lasering of the perilimbar and episcleral veins in C57/BL6 mice results in elevation of the IOP that leads to the loss of approximately 50% of the original RGC population. This RGC loss, which did not seem to progress between 2 and 8 weeks, was focal (in sectors with the apex located in the optic disc) as well as diffuse within the retina.
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