Clinical Neurology · Neuro-Ophthalmology
Visual Fields & Localization
Quick Facts
- The optic nerve head is formed from a coalescence of 1 million axons from the retinal ganglion cells.
- The optic nerve is divided into the intraocular, intraorbital, intracanalicular, and intracranial.
- An altitudinal visual field defect is suggestive of ischemic optic neuropathy but may also be seen in idiopathic optic neuritis.
- Ischemic optic neuropathy is the result of posterior ciliary artery occlusion.
- 90% of ischemic optic neuropathy are nonarteritic and related to a congenitally small optic cup and 10% may have underlying giant cell arteritis.
- 80% of patients with optic neuritis will have signal intensity abnormality within the optic nerve in STIR sequences with fat-suppressed views.
- In the Optic Neuritis Treatment Trial (ONTT), 59% of patients had cerebral white matter lesions.
- 56% of optic neuritis convert to MS in 10 years if MRI is positive and only 22% if MRI is negative.
- The fibers of the optic tract synapse in: the primary visual pathway synapses in the LGB, the pupillomotor pathway synapses in the pretectum, and the subcortical visual pathway synapses in the superior colliculus.
Localization of Visual Field and Higher Cortical Visual Dysfunction
Mapping a visual field defect to a level along the afferent visual pathway — from optic nerve through chiasm, tract, lateral geniculate nucleus, and the temporal, parietal, and occipital lobes.
| Field Defect or Syndrome | Localization |
|---|---|
| Unilateral central scotoma | Optic nerve |
| Bitemporal hemianopsia | Chiasm |
| Junctional defect (ipsilateral central scotoma and a contralateral superior temporal field cut) | Anterior chiasm or posterior optic nerve (Wilbrand knee is affected) |
| Central temporal scotomas | Posterior chiasm |
| Incongruous homonymous hemianopsia, afferent pupillary defect, and bow-tie atrophy | Optic tract |
| Homonymous sectoranopia | Lateral geniculate nucleus |
| Incongruous homonymous hemianopsia | Lateral geniculate nucleus |
| Homonymous upper quadrant defect “pie in the sky” | Temporal lobe |
| Homonymous defect, denser inferiorly | Parietal lobe |
| Gerstmann syndrome and a homonymous defect, denser inferiorly | Parietal lobe |
| Complete homonymous hemianopsia | Not well-localized to post-chiasmal location |
| Homonymous upper quadrantanopsia with macular sparing | Occipital lobe (lower bank) |
| Homonymous lower quadrantanopsia with macular sparing | Occipital lobe (upper bank) |
| Isolated homonymous defect (macular sparing) without other neurologic findings | Occipital lobe |
| Anton syndrome (cortical blindness) | Bilateral occipital lobe lesions |
| Balint syndrome | Bilateral occipitoparietal lesions |
| Alexia without agraphia | Left occipital lobe and angular gyrus |
| Central achromatopsia | Bilateral occipito-temporal lesions |
Biousse V, Newman NJ. Neuro-Ophthalmology Illustrated. Thieme; 2009: 41–3.
Occipital Lobe Syndromes
Higher-order visual syndromes that follow lesions of the occipital lobe and its association cortex.
| Syndrome | Description | Localization |
|---|---|---|
| Anton syndrome | Patients with cortical blindness who are unaware of their visual loss | Bilateral occipital lesions |
| Palinopsia | Perseveration of the visual image once the stimulus has been removed | Occipital lobe lesion |
| Prosopagnosia | Inability to recognize familiar faces | Bilateral occipitotemporal lesions |
| Achromatopsia | Abnormality of color perception | Bilateral occipitotemporal lesions |
| Balint syndrome | Triad of simultanagnosia (impaired spatial awareness of more than one object at a time), optic apraxia (difficulty in fixating the eyes), and ocular ataxia (visual misreaching) | Bilateral parieto-occipital lobes or the visual association cortex |
| Alexia without agraphia | Left occipital lobe and splenium of the corpus callosum (visual information from the intact right occipital lobe is unable to reach the language areas “angular”) |
Ahmed Koriesh, MD