Review Question - QID 218503

This patient with a history of glaucoma presenting with acute onset, painless vision loss, and fundoscopic examination showing flame hemorrhages, retinal edema, and dilated tortuous veins in the left inferonasal retina most likely has a branch retinal vein occlusion. The left nasal retina, left optic nerve, optic chiasm, right optic tract, right lateral geniculate nucleus, right optic radiations, and right primary visual cortex is the correct ordering by which visual information normally reaches the primary visual cortex.

Light is inverted as it passes through the optic axis onto the retina. Therefore light from the superior portion of the visual field falls onto the inferior portion of the retina. In contrast, light from the temporal portion of the visual field falls onto the nasal portion of the retina. Visual information then proceeds from the retina into the optic nerve. Fibers of the optic nerve subsequently pass through the optic chiasm, then the optic tract. Fibers from the nasal retina cross over to the contralateral side, while fibers from the temporal retina do not cross over. Neuronal fibers then proceed from the optic tract to the lateral geniculate nucleus (LGN) of the thalamus before passing into the optic radiations. The inferior optic radiations in the temporal lobe carry information from the inferior retina, while the superior optic radiations in the parietal lobe carry information from the superior retina. Finally, the optic radiations synapse into the primary visual cortex. Besides the main pathway for conscious visual perception, some fibers of the optic tract also relay information directly to the pretectal area and superior colliculus.

Pula et al. discuss vision dysfunction in cerebrovascular disease. The authors note that chiasmal strokes causing bitemporal hemianopia are rare due to rich collateral circulation. The authors recommend that clinicians become familiar with visual stroke syndromes to help clinically localize lesions.

Incorrect Answers:
Answer 1: Left nasal retina, left optic nerve, optic chiasm, left lateral geniculate nucleus, left optic tract, left optic radiations, and left primary visual cortex are incorrect as visual information is relayed from the optic tract to the lateral geniculate nucleus. In addition, visual information from the nasal retina crosses over at the optic chiasm to the contralateral optic tract.

Answer 2: Left nasal retina, left optic nerve, optic chiasm, left optic tract, left lateral geniculate nucleus, left optic radiations, and left primary visual cortex are incorrect as visual information from the nasal retina crosses over at the optic chiasm to the contralateral optic tract.

Answer 3: Left nasal retina, left optic nerve, optic chiasm, right lateral geniculate nucleus, right optic tract, right optic radiations, and right primary visual cortex are incorrect as visual information is relayed from the optic tract to the lateral geniculate nucleus. Information from the nasal retina crosses over at the optic chiasm to the contralateral optic tract.

Answer 5: Left temporal retina, left optic nerve, optic chiasm, left lateral geniculate nucleus, left optic tract, left optic radiations, and left primary visual cortex are incorrect as visual information is relayed from the optic tract to the lateral geniculate nucleus. Visual information from the temporal retina does not cross over at the optic chiasm.

Bullet Summary:
The visual pathway begins at the retina and proceeds through the optic nerve, optic chiasm, optic tract, lateral geniculate nucleus, optic radiations, and primary visual cortex.