| Popis: |
It is generally accepted that most of the photopic ERG response to luminance stimulation originates from sources in the distal retina. At best a very small contribution is attributed to amacrine and ganglion cells. This assertion finds support in our recent topographic study. Using the same systems analysis technique applied in the present study, we have shown that the topography of the response density to achromatic local flicker stimulation mirrors that of cone densities (Sutter and Tran, 1992). Thus, the largest signal contribution attributed to Muller cells (b-wave) can be directly related to receptor response. Based on these findings, it seemed reasonable to ask how much of this response is mediated by L- and M-cones. (S-cones add little to the response and the contribution of rods is negligible with fast photopic stimulation.) If there are ERG components originating from the two receptors populations and if they are devoid of any lateral mechanisms, they must reflect the densities of L- and M-cones (assuming equal response properties of the two cone types). These components might be found in the early a-wave obtained under stimulation conditions of M-silent and L-silent substitution. |
