What is an incongruous visual field defect?

A congruous visual field defect is identical between the two eyes, whereas an incongruous defect differs in appearance between the eyes. For lesions behind the LGN, visual field defects are generally more congruous if the lesion is located more posteriorly along the visual pathway.

What happens if there is a lesion at the optic tract?

Lesions involving the whole optic nerve cause complete blindness on the affected side, that means damage at the right optic nerve causes complete loss of vision in the right eye. Optic neuritis involving external fibers of the optic nerve causes tunnel vision.

What effects would a lesion have on the right optic nerve?

A lesion of the right optic nerve causes a total loss of vision in the right eye; it also produces a right afferent pupil deficit.

Where is the lesion in left homonymous hemianopsia?

Left Homonymous Hemianopia: This results from lesions to the optic tract in route towards the lateral geniculate body of the thalamus (location 3) as well as lesions right after the radiating fibers leave the lateral geniculate body (location 5). These lesions are often caused by strokes or neoplasms.

Which lesion causes homonymous hemianopia?

It is caused by lesions of the retrochiasmal visual pathways, ie, lesions of the optic tract, the lateral geniculate nucleus, the optic radiations, and the cerebral visual (occipital) cortex (figure 1) [1-4].

What causes a optic tract lesion?

Common etiologies. Optic tract lesions are most commonly caused by infarction (40%), tumors (32%), and trauma (17%) (Zhang et al., 2006b). Rarely, demyelinating disease may involve the optic tract in isolation (Savino et al., 1978; Rosenblatt et al., 1987).

What causes left homonymous hemianopsia?

Homonymous hemianopsia can be congenital, but is usually caused by brain injury such as from stroke, trauma, tumors, infection, or following surgery. Vascular and neoplastic (malignant or benign tumours) lesions from the optic tract, to visual cortex can cause a contralateral homonymous hemianopsia.

What causes left hemianopsia?

What causes homonymous hemianopsia? The most common cause of this type of vision loss is stroke. However, any disorder that affects the brain — including tumors, inflammation and injuries — can be a cause.

What is an optic tract?

Listen to pronunciation. (OP-tik trakt) The nerves that travel from the optic chiasm (place in the brain where some of the optic nerve fibers cross) into certain parts of the brain involved in vision.

When do you use incongruent vs incongruous?

Mathematically, congruent means having the same size and shape, being identical in form. The antonyms are incongruent and incongruence. Congruous means to be agreement or harmony, usually in an aesthetic sense. It is rarely used, while its antonym, incongruous, is more common.

What lesion causes left homonymous hemianopia?

What are lesion groups 1 2 and 3 of optic neuritis?

Lesion groups 1 and 2 result in a bowtie pattern of optic atrophy ( Fig. 3.22b) of the right optic nerve. Lesion group 3 results in mostly temporal atrophy of the left optic nerve ( Fig. 3.22b). A RAPD is often observed in the eye contralateral to the optic tract lesion.

How do optic tract lesions cause optic atrophy?

These axons are destined for the lateral geniculate nucleus, where they synapse with neurons whose axons then form the optic radiations. Therefore, chronic optic tract lesions will cause optic atrophy, often in a characteristic pattern. 1.

What are the disorders of the optic radiation?

Disorders of the optic radiation 1 Internal capsule. Postsynaptic fibers from the LGN emerge from the dorsolateral surface of the LGN to form the optic radiation, traveling posteriorly in a compact bundle within the most inferior 2 Temporal fascicle. 3 Parietal fascicle.

What type of lesion causes contralateral homonymous hemianopia?

Correct Answers: Lesions of the optic tract cause a contralateral homonymous hemianopia, which may or may not be congruent. Optic tract fibers are the axons of the ganglion cells originating in the inner layers of the retina.