Correlation of retinal function with retinal histopathology following ischemia-reperfusion in rat eyes

Abstract

Purpose. To investigate the relationship between retinal function and histopathology following retinal ischemia-reperfusion in rats. Methods. Retinal ischemia was induced in 27 Sprague-Dawley rats by raising the intraocular pressure for 60- or 90-minutes. Two weeks after the retinal ischemia-reperfusion, ganzfeld stimuli of different luminances (maximum 0.51 log cd-s/m²) were used to elicit full-field ERGs from the right (experimental) and left (control) eyes. The amplitudes of the scotopic b-waves were measured, and intensity-response curves were plotted. The b-wave amplitudes at the initial peak (Vb_IP), the dip (Vb_dip), and the maximum stimulus intensity (Vb_max) were measured. The animals were sacrificed after the ERG recordings to determine the surviving retinal cells in the inner nuclear layer (INL). Results. The log values of the Vb_IP, Vb_dip and Vb_max were linearly correlated with the number of surviving cells in the INL (r = 0.928, 0.905, and 0.913 for Vb_IP, Vb_dip and Vb_max, respectively; p < 0.0001 for each). The slope of the regression line for the Vb_dip was significantly steeper than that for the Vb_IP and Vb_max (p < 0.005). The regression line for the Vb_dip reached undetectable level of the b-wave (Conclusions. The amplitude of the scotopic b-wave is a sensitive index of the surviving INL cells. However, if one selects the stimulus intensity at the dip, the functional loss would be exaggerated in spite of the presence of cells in the INL.