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Y. Mukaida, S. Machida, A. Ushirokawa, T. Masuda, Y. Tazawa; Correlation of the Electroretinogram(ERG) b-wave with Retinal Histopathology following Ischemia-reperfusion in the Rat Retina . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1877.
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Purpose:To investigate the relationship between retinal function and histopathology following retinal damage by ischemia-reperfusion in rats. Methods:Retinal ischemia was induced in 27 Sprague-Dawley rats by raising the intraocular pressure ( IOP ). The anterior chamber of the right eye was punctured with a 27G needle connecting to a saline resorvior. The IOP was raised to 110mmHg for various periods of 30-120 minutes. Two weeks after the retinal ischemia-reperfusion, full-field ERGs were recorded from the right (experimental) and left ( control ) eyes with a maximum ganzfeld stimulus with luminance of 0.51 log cd-s/m2. The amplitudes of the scotopic b-waves to different stimulus intensities provided by increasing with 0.20- or 0.36-log-unit steps were measured. From intensity-response curves, b-wave amplitudes at initial peakVbIP)dipVbdipand maximum stimulus intensityVbmaxwere determined. The intensity producing a criterion amplitudes of 20µV was defined as the threshold for the b-wave. The animals were sacrificed after recording ERGs to assess the number of surviving retinal cells in the inner nuclear layerINL. Results:The log value of the Vbmax, VbIP and Vbdip were linearly correlated with the surviving cell numbers in INL ( r = 0.937,0.915 and 0.923 for Vbmax, VbIP and Vbdip, respectivelyP<0.0001 ). The slope of the regression line for the Vbdip was significantly steeper than the other two lines for Vbmax and VbIP (p<0.005).The Vbdip was undetectable1µVdespite approximately 30% of the cells remained in INL. The log values of the scotopic b-wave threshold was significantly correlated with cell losss in INL (r = -0.881, P<0.0001). Conclusions: The amplitudes and threshold of the scotopic b-wave are sensitive indices to study surviving retinal cells in INL. However, if one selects the stimulus intensity at the dip to evaluate retinal function, the scotopic b-wave amplitude would be extinguished despite of remaining of retinal cells in INL.
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