What is Homonymous Superior Quadrantanopia?
A visual field test is used to map the field of vision in each eye, including both the central and peripheral (side) areas, while the patient focuses on a specific central point. This test is useful for identifying areas where vision may be impaired or ‘missing’, which can help doctors pinpoint where a vision problem might be occurring along the visual pathway in the brain. These vision problems are categorized based on whether they affect one eye (unilateral) or both eyes (bilateral). Issues affecting only one eye are usually related to problems with the retina or optic nerve, which are parts of the eye. On the other hand, problems affecting both eyes often suggest issues with the visual pathways after the point where the nerves from both eyes cross over (‘chiasmal lesions’) or areas further along these pathways (‘retrochiasmal’).
There’s a particular vision problem called ‘homonymous superior quadrantanopia’, often nicknamed “pie in the sky.” It leads to impaired vision in the upper field of vision on the same side in both eyes. This issue affects both eyes and is usually attributed to a problem in the retrochiasmal pathways in the brain.
What Causes Homonymous Superior Quadrantanopia?
Homonymous superior quadrantanopia is a condition that results in a specific type of vision loss. This means that you can’t see the upper area of your field of vision in both eyes. There are many possible reasons why this could happen:
* A stroke, which is when blood flow to a part of your brain is interrupted or reduced
* A tumor, which is an abnormal growth of cells, that damages the parts of your brain that handle vision
* An aneurysm, which is a bulge or ballooning in a blood vessel in the brain
* Demyelinating diseases, where the protective covering of nerve cells in the brain, called myelin, are damaged
* Trauma or injury to the brain
* An abscess, which is a pocket of pus that forms in the brain due to an infection
* An arachnoid cyst, which is a fluid-filled sac that develops between the brain and the arachnoid membrane (one of the three layers of protective tissue covering the brain)
* Surgery on the temporal lobe of the brain, usually if the surgery involves areas more than 3 cm into the temporal lobe
* Treatment with radiosurgery for a specific type of seizure called mesial temporal lobe epilepsy
* Damage to tissue caused by radiation therapy, known as radiation necrosis
Additionally, there can be vision loss after a stroke that happens following a chiropractic neck manipulation – a procedure where a healthcare provider uses their hands or a small instrument to apply controlled force to a joint in your neck. Also, vertebrobasilar insufficiency can cause this vision loss. This is when the blood flow to the back of the brain is disrupted.
There have been rare cases where diseases like Creutzfeldt-Jakob disease, Alzheimer’s disease, Lewy body disease, non-ketotic hyperglycemia, or global ischemia have caused this type of vision loss. These conditions affect the brain in different ways, leading to a wide range of symptoms, including vision issues.
Risk Factors and Frequency for Homonymous Superior Quadrantanopia
Superior homonymous quadrantanopia is not a sickness but a sign that might indicate a problem with certain parts of the optic nerves in the temporal lobe. It’s not clear how often this visual issue occurs in the general population. However, research does show that it can appear after injuries to the temporal lobe. The most common cause, accounting for 69% of cases, is an ischemic stroke. While many patients experience vision loss on one side, about a third have superior quadrantanopia. The majority of these problems are located in the occipital lobe, but about a third are found in the optic nerves.
This type of vision loss might not be noticed if it’s mild. However, if it’s severe, it can significantly limit a person’s peripheral vision and make activities like driving difficult. The older people get, the more likely they are to experience this visual issue, as strokes and traumatic injuries become more common with age. In Australia, about 0.8% of people aged 49 years or older have some sort of visual field defect. There’s a notable link between age, high blood pressure, diabetes, and kidney issues. However, only about half of the patients with visual defects have had a stroke before.
Signs and Symptoms of Homonymous Superior Quadrantanopia
Homonymous hemianopia is a condition where a person loses half of their field of vision in both eyes. When this condition develops slowly, it is usually due to a compressive problem. But in cases where the condition appears suddenly, it is typically caused by bleeding, loss of blood supply, or inflammation.
In the early stages of acquired homonymous hemianopia, patients may not notice any vision issues, especially if the right side of the brain is affected, because the related neurological effects are subtle. But, over time, most adults will become aware of defects in their peripheral vision. Some may even start bumping into objects on the side of their blind field. Those with upper defects might hit their heads on something above them in their blind field. They may complain about not seeing the upper part of the TV screen or computer, which can also lead to reading problems if the field defect crosses the horizontal center of their vision.
Depending on the cause, symptoms of lesions in the optic radiation (the most posterior part of the internal capsule) can vary. These could include:
- Headaches
- Seizures
- Motion and sensation issues on the opposite side of the body
- Decreased consciousness
- Speech disorders
Major neurological findings are more common with parietal (related to the wall of a bodily cavity or vessel) lesions than temporal (related to time or the temples of the head) ones.
If the lesions are in the lateral geniculate ganglion (a part of the brain that processes vision), this may lead to complex vision problems as different parts of the ganglion are responsible for different areas of visual processing. The pupil’s response to light will remain normal, as the optic tract directly controls these fibers.
Most vision issues associated with the occipital lobe (part of the brain responsible for vision processing) are caused by blood vessel issues or trauma. They generally affect both eyes in the same way, without other major neurological issues.
Testing for Homonymous Superior Quadrantanopia
If you’re suspected of having a disease that’s affecting your vision, there are several tests that your doctor might use to figure out what’s causing the problem. Even if your eyesight seems normal in a basic face-to-face visual examination, your doctor may still recommend more detailed visual field testing.
This type of test is important for establishing a starting point, which can be used to track if and how your vision problem changes over time, and to see if any treatments are working. If you’re experiencing a condition called homonymous hemianopia, where you’ve lost vision in the same area in both eyes, detailed visual testing can’t provide any more information on where exactly in the visual pathway the problem lies.
However, if the loss of vision isn’t complete, the test can give two clues to your doctor about the location of the problem. Just keep in mind these clues aren’t definitive. First off, if you have a similar vision loss in both eyes, the problem is more likely to be further back in the visual pathway. For example, if the problem’s at the front of the pathway, you might have differently sized and shaped vision losses in each eye, whereas if it’s at the back, in the occipital cortex of the brain, the loss will be almost or exactly the same in both eyes.
Secondly, if the vision loss is mainly in the upper or lower half of your field of view, this can hint towards where along the pathway the issue lies. If the loss is primarily in the upper part of your vision, it’s likely the problem is in the lower part of the visual pathway, possibly involving the optic radiation (often damaged in temporal lobe lesions), or the lower part of the occipital visual cortex in the back of the brain.
Conversely, if the vision loss is in your lower field of view, it indicates damage to the upper parts of the pathway, which could be the optic radiation in the parietal lobe, or the upper part of the visual cortex above a deep groove in the brain called the calcarine fissure. Generally, for lesions in the temporal lobe of the brain, the vision issue tends not to be identical in both eyes, and may not have straight borders.
An MRI, or Magnetic Resonance Imaging, is the best tool for finding out if something in the brain, like a lesion, is causing your visual problems. But in some rare cases, an MRI might not show anything unusual. In emergency situations caused by things like internal bleeding within the brain or trauma, a CT (Computed Tomography) scan can also adequately show any problems.
Depending on the specific cause of the problem, your doctor might also recommend further laboratory tests or other studies.
Treatment Options for Homonymous Superior Quadrantanopia
If someone experiences superior quadrantanopia, which is a visual field deficiency affecting the upper quarter of the individual’s vision, attention is usually given to treating the root cause. This is because the condition doesn’t usually interfere significantly with one’s quality of life. As the visual loss is only toward one side and in the upper quarter, most patients don’t need specific corrective measures.
For patients suffering from homonymous hemianopia, a condition that results in the loss of half of the visual field in both eyes, different techniques can be helpful:
– Using a colored piece of paper can assist those who find reading individual words challenging because their defect splits the area at the back of the eye (macula). The colored paper is placed vertically along the reading page’s side, and can also be used horizontally, moving it down the lines of the page.
– Teaching those with left-side vision loss to shift their gaze to the left side of each line or to the first letter of each word. Similarly, for those with right-side vision loss, a strategy is to read till the end of a word before moving onto the next one.
Chronic sufferers of complete vision loss on one side of each eye (homonymous hemianopia) can potentially find optical assistance from devices known as prisms. However, this is useful for only a small percentage of patients. Prisms work by displacing images from the blind half of the vision toward the good half, aiding the patients in becoming aware of new objects in their blind field. Unfortunately, many patients find this approach difficult, and only about 20% to 30% continue using it.
An intriguing adaptive mechanism occurs in children with congenital or early-onset hemianopia. They often develop an outward deviation of the eye (exotropic eye) and a corresponding head turn towards the visual field defect to increase their usable visual field.
Visual occupational therapy and rehabilitation can be helpful for treating these conditions. Techniques designed to improve the movement of the eye into and within the defective field of vision may prove beneficial. Therapies that involve training to restore some lost visual field and adapt to “blindsight,” a phenomenon where patients respond to visual stimuli that they report not consciously seeing, have also been attempted. A home-based, computerized treatment called vision restoration therapy, which provides repetitive stimulation on both sides of the visual field defect, has shown benefits for many patients, especially in activities like reading and watching television.
What else can Homonymous Superior Quadrantanopia be?
While diagnosing, doctors should consider the following possible conditions:
- Optic tract lesions
- Bilateral retinal lesions
- Unilateral optic nerve injury affecting the fibers on the opposite side of the nose (known as Wilbrand knee)
What to expect with Homonymous Superior Quadrantanopia
Typically, vision loss is considered permanent, as less than 20% of patients experience a return of their lost visual field. If there’s any improvement, it generally happens within 3 to 6 months after the injury. The aim of rehabilitation is to enhance or widen the remaining visual field.
Activities like reading and driving aren’t greatly affected because the lower parts of the visual field usually remain intact.
Possible Complications When Diagnosed with Homonymous Superior Quadrantanopia
1. Brain injury due to bumping the head
2. Trouble seeing clearly at the upper edges
3. Having problems with vision, specifically seeing objects at the upper edges
Preventing Homonymous Superior Quadrantanopia
Doctors often recommend that patients with specific medical conditions take steps to prevent and manage their symptoms. For example, patients dealing with a condition that impacts their vision might need to turn their head to see in the impaired vision area. But don’t worry, most patients quickly learn to do this. In cases where the issue only affects the upper part of the visual field, this condition often does not significantly affect their daily life, and they only need to make small changes to their everyday activities.
For people with severe vision loss on one side, known as homonymous hemianopia, independent tasks like crossing the street can be difficult. It could also make driving and reading challenging because seeing an entire line of words or finding the beginning of the next line could be problematic. Relatives can support them by approaching from the side with better vision and keeping things like food, cutlery, and drinks within their clear vision area when they eat.
