What homonymous hemianopsia (HH) can be defined as is when an individual is reduced to only being able to see one side of the visual world from each eye. HH is commonly caused by a stroke and will cause a person to bump into objects or fail to see objects or people. It is the brain that is the issue in homonymous hemianopsia, rather than the eyes themselves. When the left side of the brain is injured, there is loss to the right half of the visual world of each eye. An injury to the right brain could potentially cause a loss to the left half of the visual world of each eye.
Causes of homonymous hemianopsia
Although homonymous hemianopsia can be congenital (present from birth), the primary cause in approximately 52 to 70 percent of adult cases is a stroke. About eight to 10 percent of stroke victims have homonymous hemianopsia. Other leading causes of homonymous hemianopsia include brain injury (14 percent of cases) and tumors (11 percent). Legions from the optic tract to the visual cortex can be the cause of homonymous hemianopsia.
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Other conditions that can cause homonymous hemianopsia include Alzheimer’s disease; arteriovenous malformation; cortical basal ganglion degeneration; Creutzfeldt–Jakob disease; epilepsy; lymphoma, mitochondrial encephalomyopathy; Multiple sclerosis; and vertebrobasilar dolichoectasia.
Symptoms of homonymous hemianopsia
The main symptom that arises due to homonymous hemianopsia is the experience of bumping or running into things on the side that is visually defective. It should be made clear that the condition makes those afflicted perceive a full field of vision, but in reality, information about half of their visual field isn’t being seen.
Activities such as crossing the street or driving can become fatal due to the loss of vision from oncoming traffic. Objects on one side might go unseen, such as half a plate of food being uneaten.
For those with left homonymous hemianopsia, reading will be difficult, as it will be hard to find the start of next line. Those with right homonymous hemianopsia will find reading takes a lot longer, since we read from left to right.
Visual hallucinations are a common symptom of homonymous hemianopsia. Hallucinations can take the form of recognizable objects, or they can be unformed lights, shapes, or geometric figures.
How to diagnose homonymous hemianopsia
A visual field acuity test, also known as a perimetry test, is necessary in order to diagnose homonymous hemianopsia. In this test, the patient responds to a series of flashing lights while focusing on a target. A visual field test creates a printout of the light threshold perceptible to a patient.
Your eyes may also be checked to see if the retina, macula, and optic nerve are healthy and not causing problems.
An MRI of the brain can diagnose the location of a brain injury that may be causing homonymous hemianopsia.
How to treat homonymous hemianopsia
Treatment for homonymous hemianopsia involves improving the ability to read and navigate the environment.
To improve reading, a straight edge can be used to help direct eyes to the next line of text. Another strategy is to condition the ability to capture each word within the field of vision. Additionally, text can be held at a 45- to 90-degree angle in order to read vertically; those with right hemianopsia can read down and those with left hemianopsia can read up.
Improving the ability to navigate the environment can be done by reconditioning visual habits. Eyes should be directed towards the good visual field when walking. In a new environment, a person should stop, scan from side to side, and see where objects and people are located, then picture this in the brain. Performing word and picture search puzzles can help improve the ability of the eyes to scan at close range.
If homonymous hemianopsia is caused by an underlying disorder, other treatments will be applied.
Prevention and prognosis of homonymous hemianopsia
Prevention of homonymous hemianopsia cannot be completely guaranteed with any methods. However, since homonymous hemianopsia’s main cause is a stroke, following guidelines to prevent having a stroke (lower blood pressure, lose weight, exercise more, moderate drinking, quit smoking) is an effective strategy to avoid experiencing homonymous hemianopsia.
The prognosis for homonymous hemianopsia hinges on the condition’s cause and severity of the brain injury. A severe brain injury does not have a good likelihood of complete recovery.
Total recovery of homonymous hemianopsia occurs within four weeks in 17 to 19 percent of those who experience symptoms due to a stroke. Some studies point to 55 percent of patients having some improvement within four weeks and all other improvement taking place in a 12–18-month period after the stroke.
If there is an underlying cause of a brain injury, it needs to be treated effectively. Age, diabetes, and high blood pressure will all impede full recovery from homonymous hemianopsia.
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Homonymous hemianopsia can severely affect what a person is able to see within their visual field. Because of how the brain communicates with the eyes, homonymous hemianopsia can cause a person with an injury to the left side of the brain to lose part of the right visual field in each eye, and vice versa.
If you find yourself bumping into items or having trouble navigating while walking, consider having a visual field acuity test done to diagnose homonymous hemianopsia. Strokes, tumors, and traumatic brain injuries are the leading causes of homonymous hemianopsia. By undertaking the same preventative measures to avoid a stroke, the majority of cases of homonymous hemianopsia can be prevented.
Related: How to improve vision: 11 home remedies to improve eye health
