Using DiI labeling, we were able to examine dendritic morphology of horizontal cells in the retina. Combined with PKCa and neurofilament staining, dendrites of bipolar cells and axon terminals of horizontal cells can be analyzed. In the RCS model with gradual degeneration of photoreceptors, the morphological changes occurred only after more than 50% photoreceptor loss. To elucidate if morphological changes are generally slow or very few functional synapses are able to maintain largely normal morphology of the second order neurons, we examined a light damage model, in which photoreceptors in the central area degenerate within one day. We found in the light damage model, morphological changes were observed a few days after photoreceptor degeneration, indicating that surviving functional contacts between photoreceptors and bipolar cells (and horizontal cells) are able to maintain the normal morphology of the second order neurons.