Homonymous hemianopia: half vision loss

Homonymous hemianopia is a condition characterized by the loss of vision in the same half of the visual field in both eyes. For instance, an individual might lose vision in the right side of their visual field in both eyes, or in the left side. It is crucial to understand that this vision loss does not stem from damage to the eyeball itself, but rather from damage to the visual pathways within the brain, specifically after the optic nerves have crossed. This damage disrupts the transmission of visual information from the eyes to the brain's processing centers, leading to a permanent or temporary visual field defect.

Homonymous hemianopia can be caused by various conditions affecting the visual pathways in the brain. The most common cause is a stroke, where blood flow to a part of the brain is interrupted. Other potential causes include brain tumors, head trauma, cerebral hemorrhages, and inflammatory or infectious conditions impacting brain tissue. Occasionally, other neurological conditions or cerebrovascular problems can also lead to its development. Risk factors are dependent on the underlying cause; for example, high blood pressure and diabetes increase the risk of stroke.

Individuals with homonymous hemianopia may experience significant difficulties in daily life. Symptoms often include trouble with reading, as parts of words or lines may disappear from their visual field. They might struggle with walking, bumping into objects or people on the affected side, and have difficulty identifying obstacles or hazards. Often, patients are unaware of the visual field defect and may mistakenly believe the problem is only in one eye, until they cover each eye separately and discover the defect in both. Sometimes, visual distortions or a sensation of 'seeing things that are not there' in the affected field may be described.

Diagnosis begins with a comprehensive eye examination, including visual acuity testing, eye movement assessment, and fundoscopy. The key component of diagnosis is a visual field test, which precisely maps the areas of vision loss. Once homonymous hemianopia is identified, a thorough neurological evaluation is necessary. This typically involves a full neurological examination and brain imaging, such as an MRI or CT scan, to pinpoint the location of the brain lesion and its underlying cause. Sudden onset of visual field loss requires urgent medical assessment.

Initial treatment focuses on addressing the underlying cause of homonymous hemianopia, such as managing a stroke, removing a tumor, or treating an infection. In many cases, the visual field defect cannot be fully cured, but function can often be improved through visual rehabilitation. This rehabilitation involves practicing scanning strategies, where the patient learns to move their eyes and head to 'scan' the blind area of their visual field. Special optical aids, such as prisms, can also be used to shift images into the intact visual field.

Coping with homonymous hemianopia requires adaptation and lifestyle adjustments. It is important to modify home and work environments to reduce the risk of falls or injuries. For example, rearranging furniture, improving lighting, and installing grab bars can be helpful. Driving eligibility must be assessed, as the condition can impair the ability to detect hazards on the road. In some cases, a specialized visual field test and evaluation by certified authorities are required to determine driving fitness. Psychological support and support groups can also aid in the emotional adjustment to the condition.

Follow up for homonymous hemianopia depends on the underlying cause and the extent of recovery. In cases of stroke, some improvement may occur within the first few months. Regular medical follow up with an ophthalmologist and neurologist is essential. Seek immediate medical attention if there is a sudden worsening of visual field loss, the appearance of new neurological symptoms such as limb weakness, speech difficulties, changes in consciousness, or sudden severe headaches. These symptoms may indicate the development or worsening of the underlying cause.