Light has to pass almost all layers of the retina to reach the receptor layer (600X)
At the highest magnification, almost all layers of the retina are vsible. If you think about it, the light that hits the receptor layer of rods and cones has to pass 3 layers of nerve fibers and 3 layers of nuclei before it is registered by the receptor layer. And that's after the light has traveled through the anterior of the eye!