Hemianopsia

Definition

Hemianopsia is a term that describes a loss of vision that affects half of the visual field of one eye or both eyes.

Description

Hemianopsia prevents an individual from seeing objects in half of the visual field of a particular eye. As a result, an individual suffering from hemianopsia will not see objects that are in the affected visual field.

Causes and symptoms

Conditions or injuries that affect the optic nerve can cause hemianopsia. The sequelae (aftereffects) of stroke , brain aneurysm, occlusion of the optic artery, brain tumors, or traumatic head injuries can all result in hemianopsia. Occasionally, individuals who suffer from migraine headaches may experience hemianopsia during a migrainous episode or as part of the prodromal aura that precedes the actual headache ; this type of hemianopsia resolves completely upon resolution of the headache. Transient hemianopsia can result from bouts of extremely high blood pressure (as occurs in eclampsia) or during or after a seizure. Other rare causes of hemianopsia include infections, such as encephalitis, brain abscess, progressive multifocal leukoencephalopathy , and Creutzfeldt-Jakob disease .

Symptoms of hemianopsia involve the inability to see objects in half of the visual field of one or both eyes, which may be manifested by reading difficulties, problems walking through crowded areas, frequent accidents (bumping into objects that are located in the lost visual field), or being startled at what seems to be the sudden emergence of people or objects in the visual field.

Diagnosis

Diagnosis is usually evident when basic testing reveals a blind area in half of the visual field of one or both eyes. Further testing will be necessary to uncover the underlying causative condition: CT or MRI scanning may reveal the presence of a stroke, aneurysm, or brain tumor.

Treatment team

Neurologists, ophthalmologists, and neuroophthalmologists all work with patients with hemianopsia. Occupational therapists and vision rehabilitation specialists can be integral in teaching the individual how to compensate for their vision loss.

Treatment

Treatment includes therapy to practice techniques that may help an individual overcome the obstacles of hemianopsia. For example, changing reading techniques (looking at the last part of the word, rather than the first) may improve an individual's ability to read and enjoy reading. Special scanning techniques may be taught, using a machine called a Dynavision, which will help an individual learn how to turn the head in certain ways to scan the environment and compensate for the lost visual field.

Special glasses lenses, some with mirrors or prisms incorporated, may allow an individual with hemianopsia to view a greater visual field.

Prognosis

Recovery of vision after stroke or head injury is usually maximal within the first three to six months; hemianopsia persisting after that point is usually permanent.

Special concerns

Driving can be a particular concern for people with hemianopsia. By learning new techniques for scanning the environment, some individuals can safely return to driving; others will not be able to drive safely, and will no longer be able to obtain a driver's license. This can result in significant changes in an individual's lifestyle, independence, and employability.

Resources

BOOKS

Liu, Grant T., and Nancy J. Newman. "Cranial Nerve II and Afferent Visual Pathways." In Textbook of Clinical Neurology, edited by Christopher G. Goetz. Philadelphia: W. B. Saunders Company, 2003.

Pulsinelli, William A. "Ischemic Cerebrovascular Disease." In Cecil Textbook of Internal Medicine, edited by Lee Goldman, et al. Philadelphia: W. B. Saunders Company, 2000.

ORGANIZATIONS

Lighthouse International. 111 East 59th Street, New York, NY 10022. 212-821-9200 or 800-829-0500. [email protected]. <http://www.lighthouse.org/Default.htm>.

Rosalyn Carson-Dewitt, MD