10/31 - 45 - Clinical Correlation of Visual Field Deficits

what is an *arcuate visual defect*?

(e.g., glaucoma)

what visual field defects occur from lesions in the optic tract?

*a lesion of the optic tracts would produce:* contralateral homonymous hemianopsia but *incongruous*

lesions compressing optic chiasm from above produce:

*inferior* bitemporal heteronymous defect

what lesions causes *"pie in the sky"* visual field defects? are they noncongruous or congruous if lesion is in *anterior* temporal lobe?

*injury to the INFERIOR* *optic radiation* in *Meyer's loop* causes *"pie in the sky"* visual field defects contralateral superior *homonymous* *NONcongruous* quadrantanopsia Homonymous - the visual field defect is on the same side/hemifield (right or left) in both eyes • If homonymous, must specify whether the defect on the right or left side

what fibers does the Baum's loop contain *superior* or *inferior* optic radiations? what occurs if a lesion in the *Baum's loop*? in what lobe of the brain does baum's loop go through?

*superior optic radiation* (Baum's loop) passes through the *parietal lobe* • Lesions affecting the superior parietal lobe (most common, e.g., infarct) can produce an *contralateral homonymous inferior quadrantanopia*

are all optic chiasms the same?

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define: *hemianopia* *quadrantanopia*

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what happens at the lateral geniculate nucleus?

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what is a *scotoma*?

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what visual field defects do *post-chiasmal lesions* produce? what visual field defects do *chiasmal lesions* produce?

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what visual field defects occur when lesions in the occipital lobe?

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define: *congruous* *noncongruous* where are lesions least congruous? where are lesions highly congruous?

Congruous - the visual defects look exactly the same in both eyes Noncongruous/incongruous - the visual field defect are not exactly the same in both eyes

what is *junctional scotoma*? *where is the lesion*? describe the visual defects that result.

Damage to anterior optic chiasm (willbrand's knee) junctional scotoma is *caused by compression of the knee of Wilbrand which is a loop of inferior nasal fibers.* this enters the contralateral optic nerve for a short distance before traveling in the optic tract Wilbrand's knee = Fibers from the inferonasal retina (superotemporal field) loop forward slightly before crossing in the chiasm in the setting of ipsilateral optic nerve damage (Wilbrand's knee)

what is *willbrand's knee*?

Fibers from the inferonasal retina (superotemporal field) loop forward slightly before crossing in the chiasm in the setting of ipsilateral optic nerve damage (Wilbrand's knee)

define: *homonymous* *heteronymous*

Homonymous - the visual field defect is on the same side/hemifield (right or left) in both eyes • If homonymous, must specify whether the defect on the right or left side Heteronymous - the visual field defect in one eye is on the opposite side (hemifield) than in the other eye. This term is not often used, as the most common heteronymous defect is bitemporal.

what is the most common optic nerve defect?

Most common defects: central scotoma, altitudinal scotoma, paracentral defects central scotoma - Central scotoma is an area of depressed vision that corresponds with the point of fixation and interferes with central vision. It suggests a lesion between the optic nerve head and the chiasm. a lesion to the optic nerve can cause ipsilateral monocular blindness

when does macular sparing occur?

PCA infarcts Macular sparing - the region of macular representation (posterior occipital pole) receives bilateral blood supply. It is possible for a process to spare the central 5 degrees of vision with *occipital lesions*. (Sometimes this is an artifact of fixation, as patients learn to search and "look around" the defect.) However, *macular sparing is not always present with an occipital lobe process*. Bilateral lesions without macular sparing (bilateral homonymous hemianopia) produce cortical (or "cerebral") blindness.

what is an *optic radiation*? *what do each of the following represent:* - superior optic radiation - inferior optic radiation *what is Meyer's loop?*

The Meyer loop is part of the optic radiation which sweeps back on itself into the temporal lobe, just lateral to the temporal horn of the lateral ventricle

how are visual fields tested?

Visual fields are tested with one eye at a time. The patient fixates at a point in the center where the horizontal and vertical meridians cross (which corresponds to macular vision) and some type of stimulus (target on a wand, spot of light, fingers) is presented at various points in the periphery

what is an *altitudinal visual defect*? what causes this?

a visual field defect in which either the upper or lower half of the visual field is selectively affected. the selective abnormality often creates a horizontal line across the visual field (known as "respecting the horizontal meridian"). Altitudinal defects occur in retinal vascular disease, glaucoma, and other *disorders that* *affect the eye itself*.

what is this visual field defect?

a;lskdfja;lsdkfja;ldsfkjadslf left homonymous highly congruous hemianopia (incomplete) aksldfja;lskdfjaf occipital

describe the visual field defect in this patient

alksdfjalkdfja;lskdfjals right superior quandrantanopia incongruous asldf;kajs;dflkjasdfjadsf behind the chiasm

describe the visual field defect in the photo

alskdfja;lkdfja;lsdkjfa;sdflka;sdfjl asdflkajsdf;lkajsdf heteronymous (bitemporal) respects the vertical inferiorly inferior > superior field loss left > right eye

what is this visual field defect

asldfkajdsl;fja left homonymous congruous hemianopia asdlfka;dlfja;fdlkja;sflkjsd behind the chiasm - homonymous occipital inferior involvement

what part of the retina represents: - superior visual field - inferior visual field - nasal visual field - temporal visual field which fibers remain uncrossed? which fibers cross in the optic chiasm?

axons from retinal ganglion cells project posteriorly in the optic nerves to the optic chiasm

what is a physiologic blind spot?

blind spot = small portion of the visual field of each eye that corresponds to the *position of the optic disk* within the retina. There are no photoreceptors (i.e., rods or cones) in the optic disk, and, therefore, there is no image detection in this area. May become enlarged if the optic nerve is swollen. Grey definition is wrong

what may cause a *central scotoma*?

central scotoma = an area of depressed vision that corresponds with the point of fixation and interferes with central vision. it suggests a *lesion between the optic nerve head and the chiasm*. A central scotoma, by definition, involves fixation. *Fixation refers to the point or object that one is directly looking at, so it is "dead center" of the visual field*. A central scotoma involves that spot and can extend outward from there. It is caused by either a *macular/foveal problem* or an optic nerve problem Central - scotoma involving fixation Paracentral - scotoma next to fixation but within the central 20 degrees Centrocecal (or cecocentral) - scotoma extending from fixation to the physiologic blind spot

what visual field defects occur from lesions in the *LGN*?

highly *in*congruous wedge-shaped Picassoesque visual defect

defects in occipital lobe

homonymous hemianopsia vision loss with macular sparing (if PCA infarct) occipital lobe lesions are HIGHLY congruous

describe the visual defects

left eye: - central scotoma - everything gone right eye: - Superior arcuate defect incomplete - Inferior altitudinal defect In front of optic tract because it is not congruous

lesions compressing the chiasm *from below* produce........

lesions compressing the chiasm *from below* produce SUPERIOR *bitemporal* heteronymous hemianopia (e.g., pituitary tumor) Inferior chiasm is getting compressed bitemporal hemianopsia (loss of vision in both temporal visual fields).

describe this visual defect

right temporal hemianopia denser superiorly