Visual field defects by lesion site
Eight defects of the visual pathway, each on a page of its own with a chart of both eyes’ fields drawn from the same model as the visual field defects explorer, and a table of the fibers its lesion cuts.
- Monocular blindness from an optic nerve lesion Right optic nerve: left eye loses nothing; right eye, the whole field.
- Bitemporal hemianopia Center of the optic chiasm: left eye loses the temporal half; right eye, the temporal half.
- Nasal hemianopia in one eye Right edge of the optic chiasm: left eye loses nothing; right eye, the nasal half.
- Binasal hemianopia Both outer edges of the optic chiasm: left eye loses the nasal half; right eye, the nasal half.
- Homonymous hemianopia Right optic tract: left eye loses the temporal half; right eye, the nasal half.
- Superior homonymous quadrantanopia Right Meyer’s loop: left eye loses the upper temporal quadrant; right eye, the upper nasal quadrant.
- Inferior homonymous quadrantanopia Right parietal optic radiation: left eye loses the lower temporal quadrant; right eye, the lower nasal quadrant.
- Homonymous hemianopia with macular sparing Right primary visual cortex: left eye loses the temporal half, center spared; right eye, the nasal half, center spared.
How do you localize a visual field defect?
Compare the two eyes. Loss in one eye only puts the lesion on that side, in front of the optic chiasm or at its outer edge. Opposite halves lost, as in a bitemporal hemianopia, put it at the chiasm. The same half lost in both eyes puts it behind the chiasm, on the side opposite the missing half.
Every lesion site in the model
Front to back along the pathway, the defect a complete right-sided lesion gives at each site. A left-sided lesion gives the mirror image.
| Lesion | Defect |
|---|---|
| Right optic nerve | Right monocular blindness |
| Center of the optic chiasm | Bitemporal hemianopia |
| Right edge of the optic chiasm | Right nasal hemianopia |
| Right optic tract | Left homonymous hemianopia |
| Right lateral geniculate nucleus | Left homonymous hemianopia |
| Right Meyer’s loop | Left superior homonymous quadrantanopia |
| Right parietal optic radiation | Left inferior homonymous quadrantanopia |
| Right primary visual cortex | Left homonymous hemianopia with macular sparing |
Naming a field defect
Defects are named for the part of the field that is lost, never for the lesion: hemianopia is loss of half the field, quadrantanopia loss of a quarter, and a left homonymous hemianopia comes from a right-sided lesion. Hemianopsia and quadrantanopsia are the same words with another ending.
Homonymous means both eyes lose the same side of the world; heteronymous means they lose opposite sides, bitemporal or binasal. Congruity, how alike the two eyes’ defects are, increases from the optic tract back to the cortex, because fibers from matching points of the two retinae come to lie side by side.
How the charts are drawn
Every chart shows the central 30° of each eye’s field as the patient sees it, the region an automated perimeter usually tests, with rings at 10° and 20°. The left eye’s chart is on the left with its temporal half on the left, and the right eye’s on the right with its temporal half on the right. The dark oval 15° into each temporal field and 1.5° below the horizontal is the normal blind spot, about 5.5° wide and 7.5° high; the blind spot mapper measures your own.
Each defect is drawn from a complete lesion, which every textbook draws the same way. Real lesions are usually partial, with ragged edges, and a patient’s chart is read with the history, the other eye, the optic discs and imaging.
The visual field defects explorer puts a lesion anywhere on the pathway and draws every fiber it cuts, and the brain explorer has the optic nerves, chiasm, tracts and geniculate bodies as 3D models.
Sources: Kandel, Principles of Neural Science, 6th edition, chapter 22, for the pathway and its lesions; Purves, Neuroscience, 6th edition, chapter 12, for the pathway and its lesions; Kupfer, Chumbley and Downer, Journal of Anatomy 1967;101:393, for the 53 percent of optic nerve fibers that cross at the chiasm.