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S. Machida, T. Takahashi, T. Masuda, Y. Mukaida, Y. Tazawa; Correlation of Retinal Function With Histopathology in the Rod and Cone Pathways of Light–damaged Rats . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5231.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To examine the functional and morphological changes in the rod and cone pathways following photoreceptor loss by continuous light exposure, and to correlate the rod and cone functions with the morphological changes. Methods: Fifty–four male Sprague–Dawley rats were exposed to diffuse fluorescent light of 2,000 lux for 24 or 48 hours. Two weeks after the light exposure, full–field scotopic and photopic ERGs were elicited by light stimuli with different intensities with a maximum luminance of 0.84 log cd–s/m2. The amplitudes of the a– and b–waves of the scotopic ERGs and the b–wave of the photopic ERGs were measured. The animals were sacrificed after the ERG recordings, and the number of surviving rod and cone nuclei in the outer nuclear layer was counted. Results: The logarithm (log) of amplitudes of the maximum rod a–wave (rod Vamax) and b–wave (rod Vbmax) were reduced monotonically with a decrease in the rod nucleus counts (P <0.0001, r=0.918 for the rod Vamax and 0.815 for rod Vbmax). The regression line for the rod Vamax decrease was significantly steeper than that for the rod Vbmax (P<0.005). The maximum b–wave amplitudes of the photopic ERGs (cone Vbmax) were significantly correlated with the number of cone nuclei in a log–linear fashion (P<0.0001, r=0.877). The slopes of the regression lines for the rod Vbmax and cone Vbmax were 0.0067 and 0.0140, respectively, which indicates that the amplitude of the cone b–wave was more severely affected than that of the rod b–waves by light–induced photoreceptor degeneration (P <0.005). Conclusions: The amplitudes of the rod and cone ERGs were correlated with rod and cone nucleus counts in a log–linear fashion in light–damaged rats. The functional loss with photoreceptor death had a greater effect on the cone pathway than on the rod pathway, when the retinal function was measured by the b–wave.
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