Hemianopsia

Hemianopsia is a loss of vision in one-half of the normal visual field (usually the right or left half) of one or both eyes However, if the visual field defects are identical in both eyes but affect less than half the field of vision in each eye (incomplete homonymous hemianopsia), the lesion may be in the occipital lobe; otherwise, it probably involves the parietal or temporal lobe. (See Recognizing types of hemianopsia, page 334.)

Hemianopsia is caused by a lesion affecting the optic chiasm, tract, or radiation

Defects in visual perception due to cerebral lesions are usually associated with impaired color vision.

History and physical examination

Suspect a visual field defect if the patient seems startled when you approach him from one side or if he fails to see objects placed directly in front of him. To help determine the type of defect, compare the patient’s visual fields with your own — assuming that yours are normal. First, ask the patient to cover his right eye while you cover your left eye. Then move a pen or similarly shaped object from the periphery of his (and your) uncovered eye into his field of vision. Ask the patient to indicate when he first sees the object. Does he see it at the same time you do? After you do? Repeat this test in each quadrant of both eyes. Then, for each eye, plot the defect by shading the area of a circle that corresponds to the area of vision loss.

Next, evaluate the patient’s level of consciousness (LOC), take his vital signs, and check his pupillary reaction and motor response. Ask if he has recently experienced a headache, dysarthria, or seizures. Does he have ptosis or facial or extremity weakness? Hallucinations or loss of color vision? When did neurologic symptoms start? Obtain a medical history, noting especially eye disorders, hypertension, diabetes mellitus, and recent head trauma.

Medical causes

Carotid artery aneurysm

An aneurysm in the internal carotid artery can cause contralateral or bilateral defects in the visual fields

It can also cause hemiplegia, a decreased LOC, a headache, aphasia, behavior disturbances, and unilateral hypoesthesia.

Occipital lobe lesion

The most common symptoms arising from a lesion of one occipital lobe are incomplete homonymous hemianopsia, scotomas, and impaired color vision The patient may also experience visual hallucinations —  flashes of light or color or visions of objects, people, animals, or geometric forms

These may appear in the defective field or may move toward it from the intact field.

Parietal lobe lesion

Parietal lobe lesion produces homonymous hemianopsia and sensory deficits, such as an inability to perceive body position or passive movement or to localize tactile, thermal, or vibratory stimuli It may also cause apraxia and visual or tactile agnosia.

Pituitary tumor

A tumor that compresses nerve fibers supplying the nasal half of both retinas causes complete or partial bitemporal hemianopsia that first occurs in the upper visual fields but later can progress to blindness Related findings include blurred vision, diplopia, a headache and, rarely, somnolence, hypothermia, and seizures.

Stroke

Hemianopsia can result when a hemorrhagic, thrombotic, or embolic stroke affects part of the optic pathway

Associated signs and symptoms vary according to the location and size of the stroke, but may include a decreased LOC; intellectual deficits, such as memory loss and poor judgment; personality changes; emotional lability; a headache; and seizures The patient may also develop contralateral hemiplegia, dysarthria, dysphagia, ataxia, a unilateral sensory loss, apraxia, agnosia, aphasia, blurred vision, decreased visual acuity, and diplopia

He may also experience urine retention or incontinence, constipation, and vomiting.

Special considerations

If the patient’s visual field defect is significant, further testing, such as perimetry or a tangent screen examination, may be indicated.

To avoid startling the patient, approach him from the unaffected side and position his bed so that his unaffected side faces the door. If he’s ambulatory, remove objects that could cause falls and alert him to other possible hazards. Place his clock and other personal objects within his field of vision, and avoid putting dangerous objects (such as hot dishes) where he can’t see them.

Pediatric pointers

In a child, a brain tumor is the most common cause of hemianopsia To help detect this sign, look for nonverbal clues such as the child reaching for a toy but missing it

To help him compensate for hemianopsia, place objects within his visual field; teach his parents to do this as well.

Pictures

Book Source Details

• Book Title: Handbook of Signs & Symptoms (Third Edition)
• Author(s): Springhouse
• Year of Publication: 2006
• Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2006 Lippincott Williams & Wilkins.

Other Book Chapters Related to Vision changes

Read excerpts from these other book chapters related to Vision changes:

Copyright Details: Handbook of Signs & Symptoms (Third Edition), Copyright © 2008 Williams & Wilkins.

More About Causes of Vision changes

• Back to symptom: Vision changes: Introduction (review 2057 causes)
• Next Book Extract About Vision changes: Scotoma (Handbook of Signs & Symptoms (Third Edition))
• All Book Extracts: All Online Book Extracts for Vision changes

More About This Book: Title: Handbook of Signs & Symptoms (Third Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2006 ISBN: 1-58255-402-1

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