Continuing Education Activity

The visual field test maps the vision in each individual eye by measuring the entire scope of vision when vision is focused on a central point. A visual field deficit can help to localize a lesion along the visual pathway. Homonymous superior quadrantanopia, also called “pie in the sky” causes a field deficit in the superior field of both eyes on the same side. This activity reviews the evaluation and management of homonymous superior quadrantanopia and highlights the role of the interprofessional team in evaluating and treating patients with this condition.

Objectives:

• Identify the etiology of homonymous superior quadrantanopia.
• Review the evaluation of the homonymous superior quadrantanopia.
• Outline management options available for homonymous superior quadrantanopia.
• Summarize the importance of communication amongst the interprofessional team to enhance the care of patients with homonymous superior quadrantanopia.

Introduction

The visual field test maps the vision in each eye by measuring the entire scope (central and peripheral) of vision when attention is focused on a central point. A visual field deficit can help to localize a lesion along the visual pathway. These deficits are divided, taking into consideration if they are unilateral or bilateral. Unilateral deficits are caused by retinal and optic nerve disease. Bilateral deficits are caused by chiasmal lesions or lesions affecting the retrochiasmal pathways.

Homonymous superior quadrantanopia, also called “pie in the sky,” causes a field deficit in the superior field of both eyes for the same side. This visual field deficit is bilateral and involves retrochiasmal pathways.[1]

Etiology

Homonymous superior quadrantanopia deficit can be seen in a large variety of disorders:

• Stroke (ischemic or hemorrhagic)
• Tumor causing damage to the posterior visual pathways (intra-axial primary or metastatic)
• Aneurysm
• Demyelinating disease
• Trauma
• Abscess
• Arachnoid cyst
• Temporal lobe surgery (surgery beyond 3 cm of the temporal lobe usually produces a superior quadrantanopsia, while surgery beyond 8 cm usually will produce complete homonymous hemianopia). Between 89%-91% of the patients have a deficit; those with selective amygdalohippocampectomy less pronounced than those with standard temporal lobectomy.[2]
• Radiosurgery treatment for mesial temporal lobe epilepsy (62.5% of the patients have a deficit at the 24-month follow-up)[3]
• Radiation necrosis
• Chiropractic neck manipulation after embolic stroke[4]
• Vertebrobasilar insufficiency[5]
• Rare cases (Creutzfeldt-Jakob disease, Alzheimer disease, Lewy body disease, global ischemia, and non-ketotic hyperglycemia have been reported)

Epidemiology

Superior homonymous quadrantanopia is not a disease; rather, a clinical finding that points towards a lesion of the optic radiations coursing through the temporal lobe. Scarce information is available regarding the frequency of this visual defect in the general population. However, studies documenting the frequency of a superior quadrantanopia following temporal lobe injury have been published.[6] The most common cause of the visual field defect is an ischemic stroke, comprising 69% of the cases. Most patients show homonymous hemianopia, but a third of the cases exhibit a superior quadrantanopia. Most lesions are localized in the occipital lobe, while 32% of lesions were found at the optic radiations.

The presence of a mild visual field deficit may go unnoticed in a patient. However, severe superior quadrantanopia can cause significant loss of peripheral vision and can impede activities such as driving. The incidence of a visual field defect increases with age as the older population has an increased incidence of strokes and traumatic injuries. The prevalence of a visual field defect in the Australian population 49 years or older is 0.8%.[7] There is a statistically significant relationship between age, hypertension, diabetes, and renal insufficiency. However, only about half of the patients with visual defects had a history of stroke.

Pathophysiology

The optic radiation and cortex on one side of the brain contain the visual information from the contralateral binocular visual hemifield.

Homonymous superior quadrantanopia is caused by damage to the contralateral inferior parts of the posterior visual pathway: the inferior optic radiation (temporal Meyer loop), or the inferior part of the occipital visual cortex below the calcarine fissure.[8][9] For normal visual acuity, you only need “half a macula”; hence, these patients have normal visual acuity.

The nerve fiber bundles of the geniculocalcarine tract are topographically distributed in a dorsal to the ventral array as they project from the lateral geniculate nuclei to the occipital lobe.

• Ventral fibers that transmit visual information from the inferior quadrants of the retina (superior visual field) initially travel through the anterior temporal lobe around the inferior horn of the lateral ventricle (Meyer loop) before connecting to the primary visual cortex in the inferior lip of the calcarine fissure.
• Dorsal fibers that transmit visual information from the superior quadrants of the retina (inferior visual field) travel through the posterior temporal lobe and the parietal lobe before connecting to the primary visual cortex in the superior lip of the calcarine fissure.[9]

A lesion involving the V2 and V3 extrastriate cortex may also cause a quadrantic visual field defect.[10] Bilateral superior quadrantanopsias, although rare, may occur for bilateral strokes or hemorrhages in both occipital lobes below the calcarine fissure.[9][11]

History and Physical

If homonymous hemianopia develops slowly, it is usually caused by a compressive etiology, but when it presents acutely, it is caused by hemorrhage, ischemia, and inflammation.

• Initially, patients with acquired homonymous hemianopias may not notice their field defect, especially if a right hemispheric lesion is responsible as associated neurological deficits are subtle.

• Eventually, however, most adult patients become aware of their defective peripheral vision.

• Those with dense field deficits may bump into objects in their blind hemifield.

• Superior deficits will cause the patient to hit his head with an object positioned above the head in the blind superior field. Patients may complain that they do not see the upper portion of a computer or television screen. They may have reading problems when the field deficit crosses the horizontal plane.

• The most posterior component of the internal capsule is the optic radiation. Therefore patients with lesions in this area can present with contralateral hemianesthesia.

• Depending on the etiology, the patient may present with headaches, seizures, contralateral motor deficits, contralateral sensory deficits, decreased level of consciousness, and in dominant temporal lobe lesions, the patient may be aphasic or dysphasic. Major neurological findings are much more common in parietal lesions than temporal ones.[9]

• Lesions in the lateral geniculate ganglion produce many complex deficits as the dorsal part corresponds to the macula, the lateral part corresponds to the superior visual field, and the medial portion to the inferior visual field. Pupillary reactions are normal as the pupillary fibers go directly from the optic tract to the superior colliculus.

• Most lesions at the occipital lobe are vascular or traumatic. They are usually homonymous and congruous and almost always without other major localizing neurologic findings.[9][12]

Evaluation

Even if confrontation visual field testing is normal, perimetry performing formal visual field testing is an essential part of the assessment of any patient with possible visual pathway disease. The baseline field can be established to monitor the stability of the deficit or the efficacy of treatment. If there is complete homonymous hemianopia, no further localization is possible. Partial homonymous field loss can help localize the lesion in two ways. However, neither is entirely reliable:[9][12][13] 

1. The more congruous the field defect (i.e., the more similar the field defect is in both eyes), the more posterior the lesion is likely to be; e.g., anterior optic radiation field defects are often moderately different in size and shape between the two eyes, whereas occipital cortex lesions cause an identical or nearly identical defect in both eyes.
2. If the partial defect is predominantly superior or inferior: partial superior homonymous defects are probably from damage to the inferior parts of the posterior visual pathway including the inferior optic radiation (often damaged in temporal lobe lesions), or the inferior part of the occipital visual cortex. Likewise, partial inferior defects occur from damage to the superior parts of the pathway including the superior optic radiation in the parietal lobe, or the superior part of the visual cortex superior to the calcarine fissure. In temporal lobe lesions, the visual deficit tends to be incongruous, and the inferior margin may have sloping borders and may cross the horizontal midline.

Magnetic resonance imaging (MRI) of the brain is the best modality to identify if there is a lesion in the brain causing the deficit. On rare conditions, the MRI may have no identifiable lesion. In the acute emergent cases from intracerebral hematomas and trauma, head computed tomography will adequately show the lesion. 

Specific etiologies may require further laboratory tests, non-invasive and invasive studies.

Treatment / Management

If a patient presents with a superior quadrantanopia, treatment is directed toward the underlying pathology as the visual field deficit does not affect the quality of life. As the deficit in homonymous superior quadrantanopia is toward one side and only the superior quadrant, most patients do not need correction.[3]

For patients with complete homonymous hemianopia, several techniques can be used and are described.

• Macular splitting and paracentral defects may make seeing individual words difficult. A colored piece of paper placed vertically along the left or right side of the page is often helpful when the loss of the margins is a source of the difficulty. It can also be used horizontally and moved down the lines of the page.
• Other strategies include teaching patients with left hemianopias to shift their gaze to the left side of every line and to the first letter of every word and instructing those with right hemianopias to reach the end of a word before going to the next.

Patients with chronic, dense homonymous hemianopias can be offered optical assistance from prisms, but only a minority of them will find it beneficial.

• Prism therapy should be used only in individuals who have normal mentation and in whom the hemianopia is isolated.
• A 15–45 (usually 30) diopter base-out Fresnel press-on prism can be placed on the temporal half of an eyeglass ipsilateral to the hemianopia. This optically displaces images in the blind half of the vision toward the good hemifield. A small central area should be cut out from the Fresnel prism to reduce double vision.
• The prism works by allowing patients to notice novel objects in their blind field; they must then turn the head in that direction to use their good field to see the objects more clearly.
• Unfortunately, most individuals find this too confusing, and only 20%–30% continue to use it. It certainly does not improve their vision to the point that they can drive or read normally.

Children with congenital or early-onset hemianopia may develop a rare compensatory phenomenon with an exotropic eye and head turn, both toward the field defect, an adaptive mechanism to increase the useful visual field.

Visual occupational therapy and rehabilitation can be helpful. Compensatory oculomotor strategies, designed to enhance visual saccades into and exploration within the defective hemifield, may be tried.[14] Training of blindsight and recovering some lost visual field have also been attempted. Vision restoration therapy is a costly home-based computerized treatment with repetitive stimulation on both sides of a border of a visual field defect. Many patients seem to benefit from these types of therapies in terms of reading and watching television.

Differential Diagnosis

The following should be kept in mind while making a diagnosis:

• Optic tract lesions
• Bilateral retinal lesions
• Unilateral optic nerve injury involving the contralateral inferonasal fibers (Wilbrand knee)

Prognosis

The visual field loss is usually permanent, with less than 20% of the patients regain the missing field.[14] If improvement occurs, it is within 3-6 months after the insult. Rehabilitation involves improving or expanding the existing visual field. Reading and driving are not markedly affected as the inferior fields are intact.

Complications

1. Traumatic brain injury secondary to head bumping
2. Difficulty with vision at superior margins

Consultations

An interprofessional team consisting of an ophthalmologist, neuro-ophthalmologist, neurosurgeon, neurologist, and visual occupational therapy and rehabilitation can help in the evaluation and management of the disease.

Deterrence and Patient Education

Prevention and modification of factors involved in the primary etiology should be conveyed to the patient. Affected patients are cautioned that they must turn the head to see into the defective field, but most of them learn to do that anyway. As a superior quadrantanopia usually does not affect the quality of life of the patient, they have to make only minimal adjustments to their daily routine.

In patients with dense homonymous hemianopias, crossing the street independently may be challenging. Also, the defect makes driving problematic. Many have difficulty reading, because left hemianopia may hamper their ability to find the beginning of the next line, and right hemianopia may not allow them to appreciate the entire line of words (hemianopic alexia). Family members are instructed to approach the patient from within the intact hemifield and keep food, utensils, and beverages within the patient’s intact hemifield when eating.

Enhancing Healthcare Team Outcomes

While the neuro-ophthalmologist is almost always involved in the care of patients with homonymous superior quadrantanopia, it is important to consult with an interprofessional team of specialists that include a neurologist, neurosurgeon, and neuroradiologist. The nurses are also vital members of the interprofessional group as they will monitor the patient during the treatment of the causative injury and assist with the education of the patient and family. The neuroradiologist also plays a vital role in determining the cause. Without providing a proper history, the neuroradiologist may not be sure what to look for or what additional radiologic exams may be needed. Some patients are sent for visual occupational therapy and rehabilitation. An interprofessional team that provides a holistic and integrated approach to postoperative care can help achieve the best possible outcomes.