FIGURE 1.

Schematic representation of the organized structure of a healthy retina (A). Light activation of opsins triggers photoreceptor hyperpolarization, which causes depolarization of ON-bipolar cells with cone OFF-bipolar cells in the same receptive field hyperpolarized. The ON-ganglion cells are subsequently activated and the OFF-ganglion cells inhibited (B). Degeneration begins by loss of rod photoreceptor cells and loss of outer segments on residual cone photoreceptor cells (C) followed by further cell loss and structural rearrangements in later stages of disease (D). S/M/L-cone = cone photoreceptor cells containing short, medium or long wavelength-sensitive opsins. Ip = intrinsically photosensitive ganglion cell.