Fig. 13

Transmission electron microscopy shows timeline of changes in outer plexiform layer. a Uninfected retina shows numerous rod spherules (r) each containing a single ribbon synapse (arrow) and mitochondrion (m). Cone pedicles (cp) contain multiple ribbon synapses (yellow arrows) and mitochondria (m). Inset shows magnified cone ribbon synapse with ribbon (arrow), and a typical triad consisting of two invaginating horizontal cell processes (h) and one bipolar cell process (bp). Many bipolar and horizontal cell processes are present vitread to cone pedicles (asterisks). b At 104 dpi, most rod spherules appear normal with ribbon synapses present. A cone pedicle (cp) at center, has swollen dystrophic dendritic processes at ribbon synapses (red arrow). Bipolar and horizontal cell processes are present beneath the pedicle (asterisk). c At 137 dpi the OPL appears disorganized with abnormal rod spherules (red arrow), a floating ribbon synapse (blue arrowhead) without invaginating dendritic processes, autophagic whorl (blue arrow) and a dystrophic dendrite (red arrowhead) at a ribbon synapse in a cone pedicle. Microglial cell (mg). d, e, f Examples of autophagic-like whorls (red arrows) in rod spherules at 137 dpi. Scale bars a-c = 2 µm; d, e, f = 1 µm