Topographic Visual Field Defects

Wilbrand’s knee

the crossing of inferonasal fibers travel anteriorly toward the contralateral optic nerve before passing into the optic tract is called as the

Tangent screen

is rarely used any longer and is primarily helpful for valuating patients suspected of nonorganic constriction of the visual field

Goldmann perimetry

has the advantage of charting the entire visual field and includes the far temporal periphery

Automated perimetry

this test is more sensitive, quantitative, and reproducible, but it is more time consuming and requires good patient cooperation and attention

Automated perimetry

It is the technique of choice for patients with optic nerve lesions, papilledema, chiasmal compressive lesions, and other progressive visual disorders.

total deviation

indicates the amount each point deviates from the age adjusted normal values. In this case, the more negative a number, the more abnormal that point.

pattern deviation

highlights focal abnormalities in the visual field, helping to emphasize the pattern of visual field loss

contralateral homonymous hemianopia

Retrochiasmal lesions involving the visual pathways produce a

RAPD and bilateral optic nerve pallor

The rule of congruency does not apply to optic tract lesions that are suspected when the homonymous hemianopia is associated with ____ on the side of the hemianopia and ____

Optic tract fibers

are the axons of the ganglion cells originating in the inner layers of the retina.

optic atrophy

chronic optic tract lesions will cause _ often in a characteristic pattern

Nasal half of the macula of the right eye , Nasal retina of the right eye, Temporal retina in the left eye

Lesions of the optic tract (left optic tract lesion) produce atrophy of 3 groups of retinal ganglion cell fibers

contralateral homonymous hemianopia

Lesions of the optic radiations typically produce a

optokinetic nystagmus

Lesions of the parietal lobe often impair ____ when stimuli are moved in the direction of the damaged parietal lobe

congruent

contralateral homonymous hemianopia Lesions of the occipital lobe produce

occipital infarction in the PCA

Most isolated congruent homonymous hemianopias are due to an

Tip of Occipital lobe sparing

Occlusion of the PCA often results in

small homonymous scotomatous defect

An embolic infarction of either a distal MCA or PCA branch can result in exclusive ischemia of the tip of the occipital lobe, thereby producing a _ if there is inadequate collateral circulation

anteriormost portion of the contralateral occipital cortex

There remains in each eye a temporal crescent of visual field for which there are no corresponding points in the other eye. The representation of this most peripheral 20 to 30 degrees is located in the

asymmetric bilateral homonymous hemianopias

Bilateral occipital lobe lesions will produce

symmetric

When bilateral lesions of the retrochiasmal visual pathways produce a decrease in visual acuity, the degree of visual acuity loss is always ____in both eyes, unless there are other, more anterior reasons

Macular lesions

Cause central or paracentral defects in the visual field.

Retinitis Pigmentosa

Causes progressive peripheral & midperipheral vision loss (tunnel vision).

Optic neuropathies

Cause nerve fiber bundle defects within the central 30° of the visual field.

• Arcuate defects

Arc-shaped vision loss.

• Altitudinal defects

Top or bottom half of vision missing.

• Central/Paracentral/Centrocecal scotomas

Blind spots in different central areas.

Nasal retinal fibers

Cross at the chiasm; temporal fibers do not cross.

Chiasmal lesion

Causes bitemporal hemianopia (peripheral vision loss in both eyes).

Lesion in the optic tract, optic radiations, or occipital lobe

Contralateral homonymous hemianopia (same side of vision lost in both eyes).

Complete homonymous hemianopia

Cannot localize the lesion precisely.

Incomplete homonymous hemianopia

Congruency helps localize the lesion:

Incongruent

Visual field defects differ between eyes = earlier in the pathway.

Congruent

Identical in both eyes = closer to occipital lobe.

Rule of congruency

More congruent = More posterior lesion (except optic tract lesions).

Optic tract lesion

Contralateral homonymous hemianopia, ± congruent.

Chronic optic tract lesion

Causes optic atrophy in specific patterns:

LGN lesion

Causes contralateral homonymous sectoranopia (loss of a sector of vision).

Temporal lobe lesion (Meyer's loop)

Causes contralateral superior quadrantanopia (pie-in-the-sky).

Parietal lobe lesion

Causes contralateral inferior quadrantanopia (pie-on-the-floor).

Parietal lobe lesion may also impair

Optokinetic nystagmus when moving stimuli toward the damaged side.

Unilateral occipital lobe lesion

Contralateral homonymous hemianopia (most often congruent).

PCA occlusion

May spare macular vision due to dual MCA/PCA blood supply.

Distal MCA or PCA infarction

Can cause a small homonymous scotoma.

Central 60° of vision

overlapping between both eyes.

Temporal crescent

last 20-30° peripherally and seen by only one eye.

Lesions sparing anterior occipital lobe

Spare the temporal crescent in vision.

Bilateral homonymous hemianopia

Loss of vision in the same side for both eyes.