What is homonymous hemianopia?
A condition that affects a person’s vision as a result of a neurological event.
Homonymous hemianopia is a ‘neurological vision impairment’, or a condition that affects a person’s vision as a result of a stroke, an injury to the brain, or another type of major neurological event.
Unlike eye conditions such as cataracts or glaucoma, a neurological vision impairment like homonymous hemianopia is a condition of the brain. It is caused by damage to the visual processing areas of the brain, rather than damage to the eye.
In these situations, even though your eyes may function correctly, the information received by your eyes is not sent to the brain in its full form. Alternatively, your brain may not be able to process correctly.
Understanding the biology
Each of our eyes processes a right and left ‘visual field’.
This refers to everything we can see at any given time. Your optic nerve sends the information from your left visual fields to the right side of your brain, and from your right visual fields to the left side of your brain.
As a result, the right side – or ‘hemisphere’ – of your brain is responsible for understanding the information sent from your left visual fields. Our brains are structured into two hemispheres. Usually, an incident like a stroke will occur in one of these two hemispheres, leaving the other one unaffected.
When a person has a homonymous hemianopia, half of the visual field in both eyes is lost.
How might that affect your vision?
It depends on the exact location of any issue or event in your brain. Your level of vision will change depending on your circumstances. While there are specific names for different types of visual field loss – including homonymous hemianopia, quadrantanopia, and incongruent hemianopia – they all cause a functional change in vision.
Common signs or experiences
You may not even be aware you’ve had a change in vision.
When you’re unaware of a change, it’s difficult to take action to minimise the impact on your daily life.
Whenever a person experiences a neurological injury or event, it’s common for loved ones to attribute changes in behaviour to the injury.
It is crucial that any person with a neurological vision impairment – along with their families and carers – has a complete understanding of any changes to vision before trying to adapt accordingly.
Some of the signs of a person experiencing homonymous hemianopia can include:
- Difficulty when entering a crowded room or moving through a busy space, because people seem to appear in front of you
- Anxiety leaving the home, or experiencing panic attacks while out in public
- Frequently bumping into stationary objects on one side of your body
- Difficulty reading, due to missing some of the words that are included in the text
- Loss of confidence in your own abilities
- Tendency to become confused or overwhelmed in unfamiliar situations.