Figure 12-3. Diagram of the cellular elements of the retina. Light entering the eye anteriorly passes through the full thickness of the retina to reach the rods and cones (first system of retinal neurons). Impulses arising in these cells are transmitted by the bipolar cells (second system of retinal neurons) to the ganglion cell layer. The third system of visual neurons consists of the ganglion cells and their axons, which run uninterruptedly through the optic nerve, chiasm, and optic tracts, synapsing with cells in the lateral geniculate body. (Courtesy of Dr. E.M. Chester.)
LateralventricleChiasmTemporal horn(Meyer’s loop)CalcarineareaTemporaldetourOpticnerveOpticradiationLat. geniculatebodyOptictract
Figure 12-4. The geniculocalcarine projection, showing the detour of lower fibers around the temporal horn. Note that a very small proportion of the pathway traverses the parietal lobe.
Figure 12-5. Diagrammatic depiction of the retinal projections, showing the disproportionately large representation of the macula in the lateral geniculate nucleus and visual (striate) cortex. (Redrawn by permission from Barr ML, Kiernan J: The Human Nervous System, 4th ed. Philadelphia, Lippincott, 1983.)
Figure 12-6. Hypertensive retinopathy, showing optic disc edema, cotton wool spots, hard exudates, and intraretinal hemorrhages.
Figure 12-7. Preretinal (subhyaloid) hemorrhage extending through the macular of the left eye, precipitated by strong Valsalva maneuvering.
Figure 12-8. Appearance of the fundus in central retinal artery occlusion. In addition to the paucity of blood flow in retinal vessels, the retina has a creamy gray appearance, and there is a “cherry-red spot” at the fovea. (Courtesy of Dr. Shirley Wray.)
Figure 12-9. Glistening “Hollenhorst plaque” occlusion of a superior retinal artery branch (arrow). These occlusions represent atheromatous particles or, less often, platelet-fibrin emboli. Some are asymptomatic and others are associated with segmental visual loss or are seen after central retinal artery occlusion. (Courtesy of Dr. Shirley Wray.)
Figure 12-10. Occlusion of the central retinal vein with suffusion of the veins, swelling of the disc, and florid retinal hemorrhages. (Courtesy of Dr. Shirley Wray.)
Figure 12-11. Mild papilledema with hyperemia of the disc and slight blurring of the disc margins. (Courtesy of Dr. Shirley Wray.)
Figure 12-12. Fully developed papilledema. The main characteristics are marked swelling and enlargement of the disc, vascular engorgement, obscuration of small vessels at the disc margin as a result of nerve-fiber edema, and white “cotton-wool spots” that represent superficial infarcts of the nerve-fiber layer. (Courtesy of Dr. Shirley Wray.)
Figure 12-13. Chronic papilledema with beginning optic atrophy, in which the disc stands out like a champagne cork. The hemorrhages and exudates have been absorbed, leaving a glistening residue around the disc. (Courtesy of Dr. Shirley Wray.)
Figure 12-14. Acute optic neuritis. Right, The disc is mildly swollen from an inflammatory process near the nerve head (papillitis). Left, MRI of the orbits with fat-saturation shows pathologic contrast enhancement of the right optic nerve.