Vision Defects and Vision Restoration Therapy – Glossary of Common Terms
It is easy to become confused by the array of terms used to describe vision, vision loss, and vision rehabilitation after a stroke or a brain injury. NovaVision™ has prepared this list of definitions to help educate both patients with vision loss and those who care for them.
Accommodation
Eye focusing; the eye’s ability to adjust its focus by the action of the ciliary muscle, which increases the focusing power of the lens and helps maintain clear vision.
Acuity
Clarity of vision. Depends on the sharpness of images and the sensitivity of nerve elements in the retina.
Alignment
The proper fusing (uniting) of images to each eye provides a single clear image.
Arteriovenous Malformation (AVM)
A congenital disorder occurring in the brain or spinal cord characterized by an abnormal development of a complex, tangled web of arteries, veins, and blood vessels. The most common symptoms of AVM include hemorrhaging (bleeding), seizures, headaches, and neurological problems such as paralysis, loss of speech, memory loss, or visual field defects. Treatable with NovaVision VRT™ Vision Restoration Therapy™.
Binocularity
The ability to coordinate the movements of both eyes in order to fuse two visual images into a single three-dimensional view.
Brain Abscess
Can result from direct extension of a cranial infection (e.g., osteomyelitis, mastoiditis, sinusitis, and subdural empyema from penetrating head wounds or bacterial infections) May produce brain swelling leading to visual field defects. Treatable with NovaVision Vision Restoration Therapy after infection has resolved.
Brain Tumor
An expanding benign or metastatic (i.e., spread from another location) intracranial lesion that may be a granuloma, a parasitic cyst, a hemorrhage (intracerebral, extradural, or subdural), an aneurysm, an abscess, or a neoplasm (metastatic or primary). Any of these conditions can produce visual field defects. Congenital primary intracranial neoplasms include craniopharyngioma, chordoma, germinoma, teratoma, dermoid cyst, angioma, and hemangioblastoma. Treatable with NovaVision Vision Restoration Therapy; however, stage four (end stage) metastatic tumors should be considered for treatment only on an experimental basis.
Cerebral Aneurysm
A weak bulging spot on the wall of a brain artery that appears gradually, often as a result of an injury, an infection, or heredity. In shape, a cerebral aneurism resembles a thin balloon or a weak spot on an inner tube. Many aneurysms never produce symptoms; however, a ruptured brain aneurysm (or subarachnoid hemorrhage) will often produce various neurological symptoms, including visual field defects. Treatable with NovaVision Vision Restoration Therapy.
Cognitive Disorder
A disorder that affects people’s ability to either interpret what they see and hear or to connect information from different parts of the brain. Cognitive disorders can be divided into broad categories: speech and language disorders, memory disorders, motor disorders, visuospatial disorders, attention/concentration disorders, and planning and behavior monitoring disorders. Patients with mild cognitive disorders may benefit from NovaVision Vision Restoration Therapy; however, moderately to severely impaired patients are not indicated for treatment. Scores of 20 or less on the Mini Mental Status Exam indicate moderately to severely impaired cognitive abilities, in which case patients should NOT be treated with NovaVision Vision Restoration Therapy.
Color Vision Deficiency (Color blindness)
An inability to distinguish certain colors or a defect in how colors are perceived. When associated with visual field loss, color blindness may be treatable with NovaVision Vision Restoration Therapy.
Constriction (Tunnel Vision)
A loss of peripheral vision that leaves only a central area of functional vision in one or both eyes.
Convergence
The ability to coordinate the movements of both eyes while turning them inward to maintain single vision up close.
Craniopharyngioma
A benign slow-growing brain tumor often located near the optic chiasm which may or may not produce endocrine, visual field defects, or psychological disorders. Treatable with NovaVision Vision Restoration Therapy.
Depth Perception (Stereopsis)
The ability to judge the relative distances of objects. Proper depth perception is vital to balance and coordination.
Diffuse Field Defects
Scattered spots or areas of decreased or lost vision in one or both eyes; low vision.
Diplopia (Double Vision)
A condition in which a single object is perceived as two images rather than one. Currently, a primary diagnosis of diplopia is NOT treatable with NovaVision Vision Restoration Therapy; some patients with a mild secondary diagnosis may be eligible; however, they should be screened by a VRT Center or a neuro-ophthalmologist.
Divergence
The ability to coordinate the movements of both eyes while turning them outward to maintain focus on distant objects.
Fixation
The ability to direct and maintain steady visual attention on a target.
Fusion
The union of images from each eye into a single image.
Glaucoma
Increased fluid pressure inside the eye (intraocular pressure). This pressure causes a loss of blood supply which, in turn, causes individual nerve cells to progressively die. As the optic nerve deteriorates, blind spots initially develop in the peripheral field of vision, followed by central vision loss and sometimes progressing to blindness. Currently, only research subjects with glaucoma as their primary disorder are treated by NovaVision Vision Restoration Therapy.
Head Injury
Also referred to as traumatic brain injury, closed head injury, or penetrating head injury. Frequently produces visual field defects. Head injury may result in cerebral contusion, acute and chronic subdural hematomas, epidural hematomas, and post-traumatic epilepsy. Treatable with NovaVision Vision Restoration Therapy.
Hemianopia
Decreased or lost vision in one half of the visual field in one or both eyes.
Hypothalamic-Pituitary Disorders
Patients with hypothalamic-pituitary disorders will experience some combination of:
- Symptoms or signs of a mass lesion (e.g., headaches or visual field defects)
- Hypersecretion or hyposecretion of one or more pituitary hormones
These masses frequently compress the optic chiasm, producing bitemporal hemianopias. Treatable with NovaVision Vision Restoration Therapy.
Intracerebral Hemorrhage
Usually results from the rupture of an arteriosclerotic vessel that has been exposed to arterial hypertension for a long period of time or made ischemic by local thrombosis. Less often, the cause is a congenital aneurysm or other vascular malformation. Treatable with NovaVision Vision Restoration Therapy.
Intracranial Neoplasm
Brain tumor – an expanding benign or metastatic (i.e., spread from another location) intracranial lesion that may be a granuloma, a parasitic cyst, a hemorrhage (intracerebral, extradural, or subdural), an aneurysm, an abscess, or a neoplasm (metastatic or primary). Any of these conditions can produce visual field defects. Congenital primary intracranial neoplasms include craniopharyngioma, chordoma, germinoma, teratoma, dermoid cyst, angioma, and hemangioblastoma. Treatable with NovaVision Vision Restoration Therapy.
Iris
The colored part of the eye located between the lens and cornea; regulates the entrance of light.
Macula
The most sensitive part of the retina, about the size of a pinhead; where our most detailed vision occurs.
Macular Degeneration (AMD)
A deterioration of the central portion of the retina known as the macula. Currently NOT treatable with NovaVision Vision Restoration Therapy for patients having AMD as their primary disorder. Partner clinics need to screen for the severity of the AMD as a secondary diagnosis accompanying a cerebrally induced visual field defect.
Microstrabismus
Also called microtropia, monofixation syndrome, and small-angle strabismus. A small-angle deviation (most commonly inward but outward as well) of less than five degrees with some amount of stereopsis (depth perception) and anomalous retinal correspondence (ARC). Patients with visual field defects that have microstrabismus as a secondary condition may be treatable with NovaVision Vision Restoration Therapy.
Multiple Endocrine Neoplasia – Type 1 (Wermer’s Syndrome)
A syndrome characterized by tumors of the parathyroid glands, the pancreatic islet cells, and the pituitary gland that may produce visual field defects. Treatable with NovaVision Vision Restoration Therapy.
Multiple Sclerosis
A slowly progressive disease of the central nervous system characterized by disseminated patches of demyelination in the brain and spinal cord, resulting in multiple and varied neurologic symptoms, including visual field defects, usually with remissions and exacerbations. May be treated with NovaVision Vision Restoration Therapy when the patient’s symptoms have been in remission for three to six months.
Near Point of Convergence (NPC)
The closest point at which the two eyes can maintain a single united image.
Neurologist
A physician who specializes in the treatment of patients with disease processes and injuries involving the nervous system.
Neuron
Any of the conducting cells of the nervous system.
Neuroplasticity
The brain’s ability, at the level of the neuron, to recover structurally and / or functionally after injury or disease.
NovaVision Vision Restoration Therapy
Vision therapy intended for the diagnosis and improvement of visual function in patients with impaired vision resulting from traumatic brain injury, stroke, inflammation, surgical removal of brain tumors, or brain surgery.
Occlusion
The blocking out of light. An eye can be completely or partially blocked. This technique is used to promote improved visual capabilities of the unblocked eye.
Ocular Motility
Pertaining to binocular alignment and eye muscle movement
Ocular Motor (OM)
General eye movement ability, which includes pursuits (visually tracking and/or following moving objects) and saccades (directing and coordinating eye movement as both eyes quickly and voluntarily shift from one target to another).
Optic Atrophy
Optic atrophy is a sign of chronic optic nerve disease and is not a diagnosis in itself; its presence demands a search for its cause. Dramatic return of vision can accompany reversal of certain pathologic processes (e.g., central vision and visual field defects may return after relief of pressure on the optic nerve caused by a tumor). Ability to treat with NovaVision Vision Restoration Therapy depends on whether the pathology is limited to optic nerve injury. Eye pathology, anterior ischemic optic neuropathy (AION), and ischemic optic neuropathy (ION) are not currently indicated for treatment with NovaVision Vision Restoration Therapy.
Optic Glioma
A mass (astrocytoma) created by the growth of abnormal cells, or an uncontrolled proliferation of cells, in one optic nerve, both optic nerves, the optic chiasm, or in conjunction with hypothalamic glioma. As the glioma grows, it presses and displaces optic nerve tissue and may also result in progressive loss of vision in one or both eyes. Treatable with NovaVision Vision Restoration Therapy.
Optic Nerve
A bundle of nerve fiber that connects each eye to the brain and transmits images from the retina to the brain.
Optic Pathway Lesions
The site of damage along the optic pathway determines visual field changes. Optic nerve lesions cause visual disturbances restricted to the affected eye. Lesions about the chiasm usually affect vision bilaterally. Lesions above or below the chiasm (e.g., a pituitary tumor) destroy nerve fibers supplying the inner (nasal) half of both retinas, resulting in defects in the temporal visual fields (as in bitemporal hemianopia). Lesions in the optic tract, optic radiations, or cerebral cortex produce homonymous hemianopia, with a loss of function in the right or left halves of both visual fields opposite the side affected. This is the most common type of hemianopia and is usually caused by a brain tumor or a cerebrovascular accident.
Perimetry
The measurement of a visual field function (the total area that can be seen while looking straight ahead) using targets of different sizes and brightness (light levels). The visual field is measured in degrees. VRT STATUS diagnostic measures the central 30 degrees of visual field.
Peripheral Vision
The ability to see or be aware of objects located on the outside edge of one’s field of view; side or lateral vision.
Pituitary Adenoma
A pituitary tumor (Cushing’s Disease) that frequently produces visual field defects, particularly bitemporal hemianopsia. Treatable with NovaVision Vision Restoration Therapy if managed by a physician.
Presbyopia
The natural deterioration of the eye’s ability to accommodate or to change the shape of its crystalline lens in order to maintain clear vision up close. Onset usually occurs between the ages of 40 and 45 and results in increased dependence on reading glasses. Currently, presbyopia as the primary disorder is NOT treatable with NovaVision Vision Restoration Therapy.
Prism
A wedge-shaped lens that is thicker on one edge than the other. This plastic or glass lens bends light in the opposite direction from its thicker end. Prisms can be used to measure an eye misalignment and / or treat a binocular dysfunction caused by eye coordination problems). A prism is sometimes added to glasses to help improve eyesight due to an eye misalignment or visual field loss.
Pursuits
The eye’s ability to smoothly follow a moving target.
Quadrantanopia
Decreased or lost vision in one quarter of the visual field in one or both eyes.
Radiation Injury to the Brain
Radiation treatment for cancer, leukemia, etc. may produce visual field defects. May be treated with NovaVision Vision Restoration Therapy after radiation therapy has been completed.
Retina
The innermost layer of the eye, and the neurological tissue onto which light rays are focused by the lens. The retina contains receptor cells (rods and cones) that send electrical impulses to the brain via the optic nerve when light rays are present.
Scotoma
An island-like area of lost or decreased vision in one or both eyes.
Sclera
The white protective covering of the eye.
Seizures
May occur only once or as epilepsy, a recurrent disorder of cerebral function. Epilepsy is characterized by sudden, brief attacks of altered consciousness, motor activity, and sensory perception, as well as by inappropriate behavior caused by excessive discharge of cerebral neurons. Temporary visual field defects may be caused by seizures but are generally not of a chronic nature. Patients with other indicated primary disorders (stroke, TBI, tumors, etc.) may also experience epilepsy. NovaVision Vision Restoration Therapy should be initiated only when seizures have been well regulated by medication and none have occurred in the past three months.
Subarachnoid Hemorrhage
Sudden bleeding into the subarachnoid space, one of the membranes that cover the brain and spinal cord. Head trauma is the most common cause of subarachnoid hemorrhage, followed by a ruptured congenital intracranial aneurysm. Treatable with NovaVision Vision Restoration Therapy.
Stereopsis
The ability to perceive three-dimensional depth, requiring adequate fusion of the images from each eye.
Stroke
Ischemic stroke occurs among individuals with a history of hypertension, diabetes mellitus, or signs of atherosclerosis, as well as among people with conditions that produce emboli. Several terms are used to define the possible locations of a stroke in the brain:
- Middle cerebral artery (MCA), frequently produces homononymous hemianopia
- Internal carotid artery (ICA), may produce hemianopia
- Anterior cerebral artery (ACA) – less common
- Posterior cerebral artery (PCA), frequently associated with contralateral homonymous hemianopia
- Vertebrobasilar – lower brainstem function
Stroke patients may be affected in more than one area. Treatable with NovaVision Vision Restoration Therapy.
Traumatic Brain Injury (TBI)
Also known as acquired head injury, closed head injury, and penetrating head injury. Frequently produces visual field defects. Head injury may result in cerebral contusion, acute and chronic subdural hematomas, epidural hematomas, and post-traumatic epilepsy. Treatable with NovaVision Vision Restoration Therapy.
Tunnel Vision
A constriction of the visual field, commonly caused by chronic glaucoma, retinal degeneration, a tumor, or a brain disorder that interferes with the fibers connecting the optic nerve to the brain. Only treatable with NovaVision Vision Restoration Therapy when caused by a tumor, brain surgery, or a brain disorder – not when caused by glaucoma, retinal detachment, or retinitis pigmentosa.
Vergence
To turn the eyes horizontally. Occurs as either convergence, in which the eyes turn inward, or divergence, in which they turn outward. Accommodative vergence, fusional vergence, proximal vergence, and tonic vergence are needed to maintain single vision.
Vertigo
A disordered state in which the individual becomes dizzy or feels that his or her surroundings are whirling; common in brain-injured patients. Currently NOT treatable with NovaVision Vision Restoration Therapy as the primary disorder.
Vision
A complex interaction between the eye and networks of neurons in the brain that process visual stimuli.
Visual Acuity
Sharpness or clearness of eyesight – measured at close, far (distance), and computer/reading distances.
Visual Field
The total area that can be seen while looking straight ahead. Varies among individuals, with the average range lying between 160 and 180 degrees.
Visual Pathway
The route of the nerve impulses from the retina along the optic nerve, and optic nerve radiations to the brain’s sensory cortex located at the base of the skull.
VRT Center
A clinic that offers NovaVision Vision Restoration Therapy.
Yoked Prism
A wedge-shaped lens that is thicker on one edge than the other. Yoked prisms are used to train or compensate for a binocular dysfunction (eye coordination problem) or a visual field loss.