Visual Fields: The total area or space visible in a person's peripheral vision with the eye looking straightforward.Visual Field Tests: Method of measuring and mapping the scope of vision, from central to peripheral of each eye.Vision Disorders: Visual impairments limiting one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from EYE DISEASES; OPTIC NERVE DISEASES; VISUAL PATHWAY diseases; OCCIPITAL LOBE diseases; OCULAR MOTILITY DISORDERS; and other conditions (From Newell, Ophthalmology: Principles and Concepts, 7th ed, p132).Visual Acuity: Clarity or sharpness of OCULAR VISION or the ability of the eye to see fine details. Visual acuity depends on the functions of RETINA, neuronal transmission, and the interpretative ability of the brain. Normal visual acuity is expressed as 20/20 indicating that one can see at 20 feet what should normally be seen at that distance. Visual acuity can also be influenced by brightness, color, and contrast.Visual Cortex: Area of the OCCIPITAL LOBE concerned with the processing of visual information relayed via VISUAL PATHWAYS.Visual Perception: The selecting and organizing of visual stimuli based on the individual's past experience.Evoked Potentials, Visual: The electric response evoked in the cerebral cortex by visual stimulation or stimulation of the visual pathways.Visual Pathways: Set of cell bodies and nerve fibers conducting impulses from the eyes to the cerebral cortex. It includes the RETINA; OPTIC NERVE; optic tract; and geniculocalcarine tract.Hemianopsia: Partial or complete loss of vision in one half of the visual field(s) of one or both eyes. Subtypes include altitudinal hemianopsia, characterized by a visual defect above or below the horizontal meridian of the visual field. Homonymous hemianopsia refers to a visual defect that affects both eyes equally, and occurs either to the left or right of the midline of the visual field. Binasal hemianopsia consists of loss of vision in the nasal hemifields of both eyes. Bitemporal hemianopsia is the bilateral loss of vision in the temporal fields. Quadrantanopsia refers to loss of vision in one quarter of the visual field in one or both eyes.Scotoma: A localized defect in the visual field bordered by an area of normal vision. This occurs with a variety of EYE DISEASES (e.g., RETINAL DISEASES and GLAUCOMA); OPTIC NERVE DISEASES, and other conditions.Glaucoma: An ocular disease, occurring in many forms, having as its primary characteristics an unstable or a sustained increase in the intraocular pressure which the eye cannot withstand without damage to its structure or impairment of its function. The consequences of the increased pressure may be manifested in a variety of symptoms, depending upon type and severity, such as excavation of the optic disk, hardness of the eyeball, corneal anesthesia, reduced visual acuity, seeing of colored halos around lights, disturbed dark adaptation, visual field defects, and headaches. (Dictionary of Visual Science, 4th ed)Glaucoma, Open-Angle: Glaucoma in which the angle of the anterior chamber is open and the trabecular meshwork does not encroach on the base of the iris.Photic Stimulation: Investigative technique commonly used during ELECTROENCEPHALOGRAPHY in which a series of bright light flashes or visual patterns are used to elicit brain activity.Optic Nerve Diseases: Conditions which produce injury or dysfunction of the second cranial or optic nerve, which is generally considered a component of the central nervous system. Damage to optic nerve fibers may occur at or near their origin in the retina, at the optic disk, or in the nerve, optic chiasm, optic tract, or lateral geniculate nuclei. Clinical manifestations may include decreased visual acuity and contrast sensitivity, impaired color vision, and an afferent pupillary defect.Pattern Recognition, Visual: Mental process to visually perceive a critical number of facts (the pattern), such as characters, shapes, displays, or designs.Ocular Hypertension: A condition in which the intraocular pressure is elevated above normal and which may lead to glaucoma.Vision, Ocular: The process in which light signals are transformed by the PHOTORECEPTOR CELLS into electrical signals which can then be transmitted to the brain.Vision Tests: A series of tests used to assess various functions of the eyes.Optic Disk: The portion of the optic nerve seen in the fundus with the ophthalmoscope. It is formed by the meeting of all the retinal ganglion cell axons as they enter the optic nerve.Contrast Sensitivity: The ability to detect sharp boundaries (stimuli) and to detect slight changes in luminance at regions without distinct contours. Psychophysical measurements of this visual function are used to evaluate visual acuity and to detect eye disease.Intraocular Pressure: The pressure of the fluids in the eye.Sensory Thresholds: The minimum amount of stimulus energy necessary to elicit a sensory response.Fixation, Ocular: The positioning and accommodation of eyes that allows the image to be brought into place on the FOVEA CENTRALIS of each eye.Vision, Binocular: The blending of separate images seen by each eye into one composite image.Motion Perception: The real or apparent movement of objects through the visual field.Attention: Focusing on certain aspects of current experience to the exclusion of others. It is the act of heeding or taking notice or concentrating.Eye Movements: Voluntary or reflex-controlled movements of the eye.Space Perception: The awareness of the spatial properties of objects; includes physical space.Optic Chiasm: The X-shaped structure formed by the meeting of the two optic nerves. At the optic chiasm the fibers from the medial part of each retina cross to project to the other side of the brain while the lateral retinal fibers continue on the same side. As a result each half of the brain receives information about the contralateral visual field from both eyes.Vigabatrin: An analogue of GAMMA-AMINOBUTYRIC ACID. It is an irreversible inhibitor of 4-AMINOBUTYRATE TRANSAMINASE, the enzyme responsible for the catabolism of GAMMA-AMINOBUTYRIC ACID. (From Martindale The Extra Pharmacopoeia, 31st ed)Retina: The ten-layered nervous tissue membrane of the eye. It is continuous with the OPTIC NERVE and receives images of external objects and transmits visual impulses to the brain. Its outer surface is in contact with the CHOROID and the inner surface with the VITREOUS BODY. The outer-most layer is pigmented, whereas the inner nine layers are transparent.Psychophysics: The science dealing with the correlation of the physical characteristics of a stimulus, e.g., frequency or intensity, with the response to the stimulus, in order to assess the psychologic factors involved in the relationship.Electroretinography: Recording of electric potentials in the retina after stimulation by light.Reaction Time: The time from the onset of a stimulus until a response is observed.Brain Mapping: Imaging techniques used to colocalize sites of brain functions or physiological activity with brain structures.Retinal Ganglion Cells: Neurons of the innermost layer of the retina, the internal plexiform layer. They are of variable sizes and shapes, and their axons project via the OPTIC NERVE to the brain. A small subset of these cells act as photoreceptors with projections to the SUPRACHIASMATIC NUCLEUS, the center for regulating CIRCADIAN RHYTHM.Blindness: The inability to see or the loss or absence of perception of visual stimuli. This condition may be the result of EYE DISEASES; OPTIC NERVE DISEASES; OPTIC CHIASM diseases; or BRAIN DISEASES affecting the VISUAL PATHWAYS or OCCIPITAL LOBE.Tomography, Optical Coherence: An imaging method using LASERS that is used for mapping subsurface structure. When a reflective site in the sample is at the same optical path length (coherence) as the reference mirror, the detector observes interference fringes.Diagnostic Techniques, Ophthalmological: Methods and procedures for the diagnosis of diseases of the eye or of vision disorders.Vision, Monocular: Images seen by one eye.Fovea Centralis: An area approximately 1.5 millimeters in diameter within the macula lutea where the retina thins out greatly because of the oblique shifting of all layers except the pigment epithelium layer. It includes the sloping walls of the fovea (clivus) and contains a few rods in its periphery. In its center (foveola) are the cones most adapted to yield high visual acuity, each cone being connected to only one ganglion cell. (Cline et al., Dictionary of Visual Science, 4th ed)Retinitis Pigmentosa: Hereditary, progressive degeneration of the neuroepithelium of the retina characterized by night blindness and progressive contraction of the visual field.Functional Laterality: Behavioral manifestations of cerebral dominance in which there is preferential use and superior functioning of either the left or the right side, as in the preferred use of the right hand or right foot.Nerve Fibers: Slender processes of NEURONS, including the AXONS and their glial envelopes (MYELIN SHEATH). Nerve fibers conduct nerve impulses to and from the CENTRAL NERVOUS SYSTEM.Electromagnetic Fields: Fields representing the joint interplay of electric and magnetic forces.Vision, Low: Vision considered to be inferior to normal vision as represented by accepted standards of acuity, field of vision, or motility. Low vision generally refers to visual disorders that are caused by diseases that cannot be corrected by refraction (e.g., MACULAR DEGENERATION; RETINITIS PIGMENTOSA; DIABETIC RETINOPATHY, etc.).Magnetic Resonance Imaging: Non-invasive method of demonstrating internal anatomy based on the principle that atomic nuclei in a strong magnetic field absorb pulses of radiofrequency energy and emit them as radiowaves which can be reconstructed into computerized images. The concept includes proton spin tomographic techniques.Optic Neuropathy, Ischemic: Ischemic injury to the OPTIC NERVE which usually affects the OPTIC DISK (optic neuropathy, anterior ischemic) and less frequently the retrobulbar portion of the nerve (optic neuropathy, posterior ischemic). The injury results from occlusion of arterial blood supply which may result from TEMPORAL ARTERITIS; ATHEROSCLEROSIS; COLLAGEN DISEASES; EMBOLISM; DIABETES MELLITUS; and other conditions. The disease primarily occurs in the sixth decade or later and presents with the sudden onset of painless and usually severe monocular visual loss. Anterior ischemic optic neuropathy also features optic disk edema with microhemorrhages. The optic disk appears normal in posterior ischemic optic neuropathy. (Glaser, Neuro-Ophthalmology, 2nd ed, p135)Saccades: An abrupt voluntary shift in ocular fixation from one point to another, as occurs in reading.Psychomotor Performance: The coordination of a sensory or ideational (cognitive) process and a motor activity.Ophthalmoscopy: Examination of the interior of the eye with an ophthalmoscope.Discrimination (Psychology): Differential response to different stimuli.Tonometry, Ocular: Measurement of ocular tension (INTRAOCULAR PRESSURE) with a tonometer. (Cline, et al., Dictionary of Visual Science, 4th ed)Ocular Physiological Phenomena: Processes and properties of the EYE as a whole or of any of its parts.Perceptual Disorders: Cognitive disorders characterized by an impaired ability to perceive the nature of objects or concepts through use of the sense organs. These include spatial neglect syndromes, where an individual does not attend to visual, auditory, or sensory stimuli presented from one side of the body.Low Tension Glaucoma: A form of GLAUCOMA in which chronic optic nerve damage and loss of vision normally attributable to buildup of intraocular pressure occurs despite prevailing conditions of normal intraocular pressure.Retinal DiseasesForm Perception: The sensory discrimination of a pattern shape or outline.Occipital Lobe: Posterior portion of the CEREBRAL HEMISPHERES responsible for processing visual sensory information. It is located posterior to the parieto-occipital sulcus and extends to the preoccipital notch.Cues: Signals for an action; that specific portion of a perceptual field or pattern of stimuli to which a subject has learned to respond.Pupil: The aperture in the iris through which light passes.Eyeglasses: A pair of ophthalmic lenses in a frame or mounting which is supported by the nose and ears. The purpose is to aid or improve vision. It does not include goggles or nonprescription sun glasses for which EYE PROTECTIVE DEVICES is available.Fundus Oculi: The concave interior of the eye, consisting of the retina, the choroid, the sclera, the optic disk, and blood vessels, seen by means of the ophthalmoscope. (Cline et al., Dictionary of Visual Science, 4th ed)Superior Colliculi: The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching.Blindness, Cortical: Total loss of vision in all or part of the visual field due to bilateral OCCIPITAL LOBE (i.e., VISUAL CORTEX) damage or dysfunction. Anton syndrome is characterized by the psychic denial of true, organic cortical blindness. (Adams et al., Principles of Neurology, 6th ed, p460)Orientation: Awareness of oneself in relation to time, place and person.Fluorescein Angiography: Visualization of a vascular system after intravenous injection of a fluorescein solution. The images may be photographed or televised. It is used especially in studying the retinal and uveal vasculature.Parietal Lobe: Upper central part of the cerebral hemisphere. It is located posterior to central sulcus, anterior to the OCCIPITAL LOBE, and superior to the TEMPORAL LOBES.Photography: Method of making images on a sensitized surface by exposure to light or other radiant energy.Optic Nerve: The 2nd cranial nerve which conveys visual information from the RETINA to the brain. The nerve carries the axons of the RETINAL GANGLION CELLS which sort at the OPTIC CHIASM and continue via the OPTIC TRACTS to the brain. The largest projection is to the lateral geniculate nuclei; other targets include the SUPERIOR COLLICULI and the SUPRACHIASMATIC NUCLEI. Though known as the second cranial nerve, it is considered part of the CENTRAL NERVOUS SYSTEM.Geniculate Bodies: Part of the DIENCEPHALON inferior to the caudal end of the dorsal THALAMUS. Includes the lateral geniculate body which relays visual impulses from the OPTIC TRACT to the calcarine cortex, and the medial geniculate body which relays auditory impulses from the lateral lemniscus to the AUDITORY CORTEX.Tomography: Imaging methods that result in sharp images of objects located on a chosen plane and blurred images located above or below the plane.Flicker Fusion: The point or frequency at which all flicker of an intermittent light stimulus disappears.Macaca mulatta: A species of the genus MACACA inhabiting India, China, and other parts of Asia. The species is used extensively in biomedical research and adapts very well to living with humans.ReadingVisually Impaired Persons: Persons with loss of vision such that there is an impact on activities of daily living.Models, Neurological: Theoretical representations that simulate the behavior or activity of the neurological system, processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.Glare: Relatively bright light, or the dazzling sensation of relatively bright light, which produces unpleasantness or discomfort, or which interferes with optimal VISION, OCULAR. (Cline et al., Dictionary of Visual Science, 4th ed)Papilledema: Swelling of the OPTIC DISK, usually in association with increased intracranial pressure, characterized by hyperemia, blurring of the disk margins, microhemorrhages, blind spot enlargement, and engorgement of retinal veins. Chronic papilledema may cause OPTIC ATROPHY and visual loss. (Miller et al., Clinical Neuro-Ophthalmology, 4th ed, p175)Magnetic Fields: Areas of attractive or repulsive force surrounding MAGNETS.Reproducibility of Results: The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.Refractive Errors: Deviations from the average or standard indices of refraction of the eye through its dioptric or refractive apparatus.Time Factors: Elements of limited time intervals, contributing to particular results or situations.Sensory Deprivation: The absence or restriction of the usual external sensory stimuli to which the individual responds.Cats: The domestic cat, Felis catus, of the carnivore family FELIDAE, comprising over 30 different breeds. The domestic cat is descended primarily from the wild cat of Africa and extreme southwestern Asia. Though probably present in towns in Palestine as long ago as 7000 years, actual domestication occurred in Egypt about 4000 years ago. (From Walker's Mammals of the World, 6th ed, p801)Dark Adaptation: Adjustment of the eyes under conditions of low light. The sensitivity of the eye to light is increased during dark adaptation.Optic Neuritis: Inflammation of the optic nerve. Commonly associated conditions include autoimmune disorders such as MULTIPLE SCLEROSIS, infections, and granulomatous diseases. Clinical features include retro-orbital pain that is aggravated by eye movement, loss of color vision, and contrast sensitivity that may progress to severe visual loss, an afferent pupillary defect (Marcus-Gunn pupil), and in some instances optic disc hyperemia and swelling. Inflammation may occur in the portion of the nerve within the globe (neuropapillitis or anterior optic neuritis) or the portion behind the globe (retrobulbar neuritis or posterior optic neuritis).Amblyopia: A nonspecific term referring to impaired vision. Major subcategories include stimulus deprivation-induced amblyopia and toxic amblyopia. Stimulus deprivation-induced amblyopia is a developmental disorder of the visual cortex. A discrepancy between visual information received by the visual cortex from each eye results in abnormal cortical development. STRABISMUS and REFRACTIVE ERRORS may cause this condition. Toxic amblyopia is a disorder of the OPTIC NERVE which is associated with ALCOHOLISM, tobacco SMOKING, and other toxins and as an adverse effect of the use of some medications.Color Vision Defects: Defects of color vision are mainly hereditary traits but can be secondary to acquired or developmental abnormalities in the CONES (RETINA). Severity of hereditary defects of color vision depends on the degree of mutation of the ROD OPSINS genes (on X CHROMOSOME and CHROMOSOME 3) that code the photopigments for red, green and blue.Automobile Driving: The effect of environmental or physiological factors on the driver and driving ability. Included are driving fatigue, and the effect of drugs, disease, and physical disabilities on driving.Color Vision: Function of the human eye that is used in bright illumination or in daylight (at photopic intensities). Photopic vision is performed by the three types of RETINAL CONE PHOTORECEPTORS with varied peak absorption wavelengths in the color spectrum (from violet to red, 400 - 700 nm).Pupil Disorders: Conditions which affect the structure or function of the pupil of the eye, including disorders of innervation to the pupillary constrictor or dilator muscles, and disorders of pupillary reflexes.Neurons: The basic cellular units of nervous tissue. Each neuron consists of a body, an axon, and dendrites. Their purpose is to receive, conduct, and transmit impulses in the NERVOUS SYSTEM.Color Perception: Mental processing of chromatic signals (COLOR VISION) from the eye by the VISUAL CORTEX where they are converted into symbolic representations. Color perception involves numerous neurons, and is influenced not only by the distribution of wavelengths from the viewed object, but also by its background color and brightness contrast at its boundary.Sensitivity and Specificity: Binary classification measures to assess test results. Sensitivity or recall rate is the proportion of true positives. Specificity is the probability of correctly determining the absence of a condition. (From Last, Dictionary of Epidemiology, 2d ed)Analysis of Variance: A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.Disease Progression: The worsening of a disease over time. This concept is most often used for chronic and incurable diseases where the stage of the disease is an important determinant of therapy and prognosis.Macula Lutea: An oval area in the retina, 3 to 5 mm in diameter, usually located temporal to the posterior pole of the eye and slightly below the level of the optic disk. It is characterized by the presence of a yellow pigment diffusely permeating the inner layers, contains the fovea centralis in its center, and provides the best phototropic visual acuity. It is devoid of retinal blood vessels, except in its periphery, and receives nourishment from the choriocapillaris of the choroid. (From Cline et al., Dictionary of Visual Science, 4th ed)Image Processing, Computer-Assisted: A technique of inputting two-dimensional images into a computer and then enhancing or analyzing the imagery into a form that is more useful to the human observer.Depth Perception: Perception of three-dimensionality.Adaptation, Ocular: The adjustment of the eye to variations in the intensity of light. Light adaptation is the adjustment of the eye when the light threshold is increased; DARK ADAPTATION when the light is greatly reduced. (From Cline et al., Dictionary of Visual Science, 4th ed)Strabismus: Misalignment of the visual axes of the eyes. In comitant strabismus the degree of ocular misalignment does not vary with the direction of gaze. In noncomitant strabismus the degree of misalignment varies depending on direction of gaze or which eye is fixating on the target. (Miller, Walsh & Hoyt's Clinical Neuro-Ophthalmology, 4th ed, p641)Field Dependence-Independence: The ability to respond to segments of the perceptual experience rather than to the whole.Dominance, Cerebral: Dominance of one cerebral hemisphere over the other in cerebral functions.Glaucoma, Angle-Closure: A form of glaucoma in which the intraocular pressure increases because the angle of the anterior chamber is blocked and the aqueous humor cannot drain from the anterior chamber.Macaca: A genus of the subfamily CERCOPITHECINAE, family CERCOPITHECIDAE, consisting of 16 species inhabiting forests of Africa, Asia, and the islands of Borneo, Philippines, and Celebes.Optic Atrophy: Atrophy of the optic disk which may be congenital or acquired. This condition indicates a deficiency in the number of nerve fibers which arise in the RETINA and converge to form the OPTIC DISK; OPTIC NERVE; OPTIC CHIASM; and optic tracts. GLAUCOMA; ISCHEMIA; inflammation, a chronic elevation of intracranial pressure, toxins, optic nerve compression, and inherited conditions (see OPTIC ATROPHIES, HEREDITARY) are relatively common causes of this condition.Trabeculectomy: Any surgical procedure for treatment of glaucoma by means of puncture or reshaping of the trabecular meshwork. It includes goniotomy, trabeculectomy, and laser perforation.Optical Illusions: An illusion of vision usually affecting spatial relations.Size Perception: The sensory interpretation of the dimensions of objects.Eye Diseases: Diseases affecting the eye.Follow-Up Studies: Studies in which individuals or populations are followed to assess the outcome of exposures, procedures, or effects of a characteristic, e.g., occurrence of disease.Phosphenes: A subjective visual sensation with the eyes closed and in the absence of light. Phosphenes can be spontaneous, or induced by chemical, electrical, or mechanical (pressure) stimuli which cause the visual field to light up without optical inputs.Retinal Cone Photoreceptor Cells: Photosensitive afferent neurons located primarily within the FOVEA CENTRALIS of the MACULA LUTEA. There are three major types of cone cells (red, blue, and green) whose photopigments have different spectral sensitivity curves. Retinal cone cells operate in daylight vision (at photopic intensities) providing color recognition and central visual acuity.Distance Perception: The act of knowing or the recognition of a distance by recollective thought, or by means of a sensory process which is under the influence of set and of prior experience.Eye: The organ of sight constituting a pair of globular organs made up of a three-layered roughly spherical structure specialized for receiving and responding to light.Pseudotumor Cerebri: A condition marked by raised intracranial pressure and characterized clinically by HEADACHES; NAUSEA; PAPILLEDEMA, peripheral constriction of the visual fields, transient visual obscurations, and pulsatile TINNITUS. OBESITY is frequently associated with this condition, which primarily affects women between 20 and 44 years of age. Chronic PAPILLEDEMA may lead to optic nerve injury (see OPTIC NERVE DISEASES) and visual loss (see BLINDNESS).Vision Screening: Application of tests and examinations to identify visual defects or vision disorders occurring in specific populations, as in school children, the elderly, etc. It is differentiated from VISION TESTS, which are given to evaluate/measure individual visual performance not related to a specific population.Lighting: The illumination of an environment and the arrangement of lights to achieve an effect or optimal visibility. Its application is in domestic or in public settings and in medical and non-medical environments.Prospective Studies: Observation of a population for a sufficient number of persons over a sufficient number of years to generate incidence or mortality rates subsequent to the selection of the study group.Macular Degeneration: Degenerative changes in the RETINA usually of older adults which results in a loss of vision in the center of the visual field (the MACULA LUTEA) because of damage to the retina. It occurs in dry and wet forms.Color: The visually perceived property of objects created by absorption or reflection of specific wavelengths of light.Pituitary Neoplasms: Neoplasms which arise from or metastasize to the PITUITARY GLAND. The majority of pituitary neoplasms are adenomas, which are divided into non-secreting and secreting forms. Hormone producing forms are further classified by the type of hormone they secrete. Pituitary adenomas may also be characterized by their staining properties (see ADENOMA, BASOPHIL; ADENOMA, ACIDOPHIL; and ADENOMA, CHROMOPHOBE). Pituitary tumors may compress adjacent structures, including the HYPOTHALAMUS, several CRANIAL NERVES, and the OPTIC CHIASM. Chiasmal compression may result in bitemporal HEMIANOPSIA.Illusions: The misinterpretation of a real external, sensory experience.Night Vision: Function of the human eye that is used in dim illumination (scotopic intensities) or at nighttime. Scotopic vision is performed by RETINAL ROD PHOTORECEPTORS with high sensitivity to light and peak absorption wavelength at 507 nm near the blue end of the spectrum.Reflex, Pupillary: Constriction of the pupil in response to light stimulation of the retina. It refers also to any reflex involving the iris, with resultant alteration of the diameter of the pupil. (Cline et al., Dictionary of Visual Science, 4th ed)Perceptual Distortion: Lack of correspondence between the way a stimulus is commonly perceived and the way an individual perceives it under given conditions.Color Perception Tests: Type of vision test used to determine COLOR VISION DEFECTS.Dominance, Ocular: The functional superiority and preferential use of one eye over the other. The term is usually applied to superiority in sighting (VISUAL PERCEPTION) or motor task but not difference in VISUAL ACUITY or dysfunction of one of the eyes. Ocular dominance can be modified by visual input and NEUROTROPHIC FACTORS.Light: That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.Lasers: An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum.Temporal Lobe: Lower lateral part of the cerebral hemisphere responsible for auditory, olfactory, and semantic processing. It is located inferior to the lateral fissure and anterior to the OCCIPITAL LOBE.Ophthalmology: A surgical specialty concerned with the structure and function of the eye and the medical and surgical treatment of its defects and diseases.Albinism, Ocular: Albinism affecting the eye in which pigment of the hair and skin is normal or only slightly diluted. The classic type is X-linked (Nettleship-Falls), but an autosomal recessive form also exists. Ocular abnormalities may include reduced pigmentation of the iris, nystagmus, photophobia, strabismus, and decreased visual acuity.Myopia: A refractive error in which rays of light entering the EYE parallel to the optic axis are brought to a focus in front of the RETINA when accommodation (ACCOMMODATION, OCULAR) is relaxed. This results from an overly curved CORNEA or from the eyeball being too long from front to back. It is also called nearsightedness.Galago: A genus of the family Lorisidae having four species which inhabit the forests and bush regions of Africa south of the Sahara and some nearby islands. The four species are G. alleni, G. crassicaudatus, G. demidovii, and G. senegalensis. There is another genus, Euoticus, containing two species which some authors have included in the Galago genus.Automobile Driver Examination: Government required written and driving test given to individuals prior to obtaining an operator's license.Algorithms: A procedure consisting of a sequence of algebraic formulas and/or logical steps to calculate or determine a given task.Refraction, Ocular: Refraction of LIGHT effected by the media of the EYE.Perceptual Masking: The interference of one perceptual stimulus with another causing a decrease or lessening in perceptual effectiveness.Optic Disk Drusen: Optic disk bodies composed primarily of acid mucopolysaccharides that may produce pseudopapilledema (elevation of the optic disk without associated INTRACRANIAL HYPERTENSION) and visual field deficits. Drusen may also occur in the retina (see RETINAL DRUSEN). (Miller et al., Clinical Neuro-Ophthalmology, 4th ed, p355)Gonioscopy: Examination of the angle of the anterior chamber of the eye with a specialized optical instrument (gonioscope) or a contact prism lens.Ophthalmologic Surgical Procedures: Surgery performed on the eye or any of its parts.Electrooculography: Recording of the average amplitude of the resting potential arising between the cornea and the retina in light and dark adaptation as the eyes turn a standard distance to the right and the left. The increase in potential with light adaptation is used to evaluate the condition of the retinal pigment epithelium.Optometry: The professional practice of primary eye and vision care that includes the measurement of visual refractive power and the correction of visual defects with lenses or glasses.Adaptation, Physiological: The non-genetic biological changes of an organism in response to challenges in its ENVIRONMENT.Optic Nerve Neoplasms: Benign and malignant neoplasms that arise from the optic nerve or its sheath. OPTIC NERVE GLIOMA is the most common histologic type. Optic nerve neoplasms tend to cause unilateral visual loss and an afferent pupillary defect and may spread via neural pathways to the brain.Retinoscopy: An objective determination of the refractive state of the eye (NEARSIGHTEDNESS; FARSIGHTEDNESS; ASTIGMATISM). By using a RETINOSCOPE, the amount of correction and the power of lens needed can be determined.Cataract: Partial or complete opacity on or in the lens or capsule of one or both eyes, impairing vision or causing blindness. The many kinds of cataract are classified by their morphology (size, shape, location) or etiology (cause and time of occurrence). (Dorland, 27th ed)Anterior Temporal Lobectomy: A neurosurgical procedure that removes the anterior TEMPORAL LOBE including the medial temporal structures of CEREBRAL CORTEX; AMYGDALA; HIPPOCAMPUS; and the adjacent PARAHIPPOCAMPAL GYRUS. This procedure is generally used for the treatment of intractable temporal epilepsy (EPILEPSY, TEMPORAL LOBE).Retrospective Studies: Studies used to test etiologic hypotheses in which inferences about an exposure to putative causal factors are derived from data relating to characteristics of persons under study or to events or experiences in their past. The essential feature is that some of the persons under study have the disease or outcome of interest and their characteristics are compared with those of unaffected persons.Face: The anterior portion of the head that includes the skin, muscles, and structures of the forehead, eyes, nose, mouth, cheeks, and jaw.Electroencephalography: Recording of electric currents developed in the brain by means of electrodes applied to the scalp, to the surface of the brain, or placed within the substance of the brain.Action Potentials: Abrupt changes in the membrane potential that sweep along the CELL MEMBRANE of excitable cells in response to excitation stimuli.Learning: Relatively permanent change in behavior that is the result of past experience or practice. The concept includes the acquisition of knowledge.Telescopes: Instruments used to observe distant objects.Nystagmus, Optokinetic: Normal nystagmus produced by looking at objects moving across the field of vision.Evoked Potentials: Electrical responses recorded from nerve, muscle, SENSORY RECEPTOR, or area of the CENTRAL NERVOUS SYSTEM following stimulation. They range from less than a microvolt to several microvolts. The evoked potential can be auditory (EVOKED POTENTIALS, AUDITORY), somatosensory (EVOKED POTENTIALS, SOMATOSENSORY), visual (EVOKED POTENTIALS, VISUAL), or motor (EVOKED POTENTIALS, MOTOR), or other modalities that have been reported.Acoustic Stimulation: Use of sound to elicit a response in the nervous system.Linear Models: Statistical models in which the value of a parameter for a given value of a factor is assumed to be equal to a + bx, where a and b are constants. The models predict a linear regression.Rotation: Motion of an object in which either one or more points on a line are fixed. It is also the motion of a particle about a fixed point. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)Macaca fascicularis: A species of the genus MACACA which typically lives near the coast in tidal creeks and mangrove swamps primarily on the islands of the Malay peninsula.Posterior Thalamic Nuclei: A transitional diencephalic zone of the thalamus consisting of complex and varied cells lying caudal to the VENTRAL POSTEROLATERAL NUCLEUS, medial to the rostral part of the PULVINAR, and dorsal to the MEDIAL GENICULATE BODY. It contains the limitans, posterior, suprageniculate, and submedial nuclei.Aberrometry: The use of an aberrometer to measure eye tissue imperfections or abnormalities based on the way light passes through the eye which affects the ability of the eye to focus properly.Discrimination Learning: Learning that is manifested in the ability to respond differentially to various stimuli.Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.Perceptual Closure: The tendency to perceive an incomplete pattern or object as complete or whole. This includes the Gestalt Law of Closure.Diagnosis, Computer-Assisted: Application of computer programs designed to assist the physician in solving a diagnostic problem.Vision Disparity: The difference between two images on the retina when looking at a visual stimulus. This occurs since the two retinas do not have the same view of the stimulus because of the location of our eyes. Thus the left eye does not get exactly the same view as the right eye.Brain: The part of CENTRAL NERVOUS SYSTEM that is contained within the skull (CRANIUM). Arising from the NEURAL TUBE, the embryonic brain is comprised of three major parts including PROSENCEPHALON (the forebrain); MESENCEPHALON (the midbrain); and RHOMBENCEPHALON (the hindbrain). The developed brain consists of CEREBRUM; CEREBELLUM; and other structures in the BRAIN STEM.Scanning Laser Polarimetry: A technique of diagnostic imaging of RETINA or CORNEA of the human eye involving the measurement and interpretation of polarizing ELECTROMAGNETIC WAVES such as radio or light waves. It is helpful in the diagnosis of GLAUCOMA; MACULAR DEGENERATION; and other retinal disorders.Cataract Extraction: The removal of a cataractous CRYSTALLINE LENS from the eye.Agnosia: Loss of the ability to comprehend the meaning or recognize the importance of various forms of stimulation that cannot be attributed to impairment of a primary sensory modality. Tactile agnosia is characterized by an inability to perceive the shape and nature of an object by touch alone, despite unimpaired sensation to light touch, position, and other primary sensory modalities.Pursuit, Smooth: Eye movements that are slow, continuous, and conjugate and occur when a fixed object is moved slowly.Timolol: A beta-adrenergic antagonist similar in action to PROPRANOLOL. The levo-isomer is the more active. Timolol has been proposed as an antihypertensive, antiarrhythmic, antiangina, and antiglaucoma agent. It is also used in the treatment of MIGRAINE DISORDERS and tremor.Cerebral Cortex: The thin layer of GRAY MATTER on the surface of the CEREBRAL HEMISPHERES that develops from the TELENCEPHALON and folds into gyri and sulchi. It reaches its highest development in humans and is responsible for intellectual faculties and higher mental functions.Computer Simulation: Computer-based representation of physical systems and phenomena such as chemical processes.False Positive Reactions: Positive test results in subjects who do not possess the attribute for which the test is conducted. The labeling of healthy persons as diseased when screening in the detection of disease. (Last, A Dictionary of Epidemiology, 2d ed)Pituitary Apoplexy: The sudden loss of blood supply to the PITUITARY GLAND, leading to tissue NECROSIS and loss of function (PANHYPOPITUITARISM). The most common cause is hemorrhage or INFARCTION of a PITUITARY ADENOMA. It can also result from acute hemorrhage into SELLA TURCICA due to HEAD TRAUMA; INTRACRANIAL HYPERTENSION; or other acute effects of central nervous system hemorrhage. Clinical signs include severe HEADACHE; HYPOTENSION; bilateral visual disturbances; UNCONSCIOUSNESS; and COMA.Memory: Complex mental function having four distinct phases: (1) memorizing or learning, (2) retention, (3) recall, and (4) recognition. Clinically, it is usually subdivided into immediate, recent, and remote memory.Automation: Controlled operation of an apparatus, process, or system by mechanical or electronic devices that take the place of human organs of observation, effort, and decision. (From Webster's Collegiate Dictionary, 1993)Nerve Compression Syndromes: Mechanical compression of nerves or nerve roots from internal or external causes. These may result in a conduction block to nerve impulses (due to MYELIN SHEATH dysfunction) or axonal loss. The nerve and nerve sheath injuries may be caused by ISCHEMIA; INFLAMMATION; or a direct mechanical effect.Signal Detection, Psychological: Psychophysical technique that permits the estimation of the bias of the observer as well as detectability of the signal (i.e., stimulus) in any sensory modality. (From APA, Thesaurus of Psychological Index Terms, 8th ed.)Eye Movement Measurements: Methods and procedures for recording EYE MOVEMENTS.Vitrectomy: Removal of the whole or part of the vitreous body in treating endophthalmitis, diabetic retinopathy, retinal detachment, intraocular foreign bodies, and some types of glaucoma.Injections, Intraocular: The administration of substances into the eye with a hypodermic syringe.Sensory Aids: Devices that help people with impaired sensory responses.Anticonvulsants: Drugs used to prevent SEIZURES or reduce their severity.Motion: Physical motion, i.e., a change in position of a body or subject as a result of an external force. It is distinguished from MOVEMENT, a process resulting from biological activity.Onchocerciasis, Ocular: Filarial infection of the eyes transmitted from person to person by bites of Onchocerca volvulus-infected black flies. The microfilariae of Onchocerca are thus deposited beneath the skin. They migrate through various tissues including the eye. Those persons infected have impaired vision and up to 20% are blind. The incidence of eye lesions has been reported to be as high as 30% in Central America and parts of Africa.Neuronal Plasticity: The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.Lenses: Pieces of glass or other transparent materials used for magnification or increased visual acuity.Electrophysiology: The study of the generation and behavior of electrical charges in living organisms particularly the nervous system and the effects of electricity on living organisms.ROC Curve: A graphic means for assessing the ability of a screening test to discriminate between healthy and diseased persons; may also be used in other studies, e.g., distinguishing stimuli responses as to a faint stimuli or nonstimuli.Craniopharyngioma: A benign pituitary-region neoplasm that originates from Rathke's pouch. The two major histologic and clinical subtypes are adamantinous (or classical) craniopharyngioma and papillary craniopharyngioma. The adamantinous form presents in children and adolescents as an expanding cystic lesion in the pituitary region. The cystic cavity is filled with a black viscous substance and histologically the tumor is composed of adamantinomatous epithelium and areas of calcification and necrosis. Papillary craniopharyngiomas occur in adults, and histologically feature a squamous epithelium with papillations. (From Joynt, Clinical Neurology, 1998, Ch14, p50)Expert Systems: Computer programs based on knowledge developed from consultation with experts on a problem, and the processing and/or formalizing of this knowledge using these programs in such a manner that the problems may be solved.Reference Values: The range or frequency distribution of a measurement in a population (of organisms, organs or things) that has not been selected for the presence of disease or abnormality.Movement: The act, process, or result of passing from one place or position to another. It differs from LOCOMOTION in that locomotion is restricted to the passing of the whole body from one place to another, while movement encompasses both locomotion but also a change of the position of the whole body or any of its parts. Movement may be used with reference to humans, vertebrate and invertebrate animals, and microorganisms. Differentiate also from MOTOR ACTIVITY, movement associated with behavior.Optic Lobe, Nonmammalian: In invertebrate zoology, a lateral lobe of the FOREBRAIN in certain ARTHROPODS. In vertebrate zoology, either of the corpora bigemina of non-mammalian VERTEBRATES. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed, p1329)Brain Diseases: Pathologic conditions affecting the BRAIN, which is composed of the intracranial components of the CENTRAL NERVOUS SYSTEM. This includes (but is not limited to) the CEREBRAL CORTEX; intracranial white matter; BASAL GANGLIA; THALAMUS; HYPOTHALAMUS; BRAIN STEM; and CEREBELLUM.Microelectrodes: Electrodes with an extremely small tip, used in a voltage clamp or other apparatus to stimulate or record bioelectric potentials of single cells intracellularly or extracellularly. (Dorland, 28th ed)
SP and visual sensitivity of FEF neurons. (A) Example o | Open-iSP and visual sensitivity of FEF neurons. (A) Example of FEF neuron tested during step-ramp pursuit with target blink. Response ... following the start of leftward visual motion. (C) Proportional distributions of large-field visual and SP responses in ... following the start of leftward visual motion. (C) Proportional distributions of large-field visual and SP responses in ... 3B, left) or a large-field visual stimulus (Fig. 3B, right) was moved in a direction and speed like that used during SP eye ...
Special TestingThis technique for assessing a patient's visual field involves the use of a target best described as a sine wave grating of a ... The target is shown at different intensities and positions in order to plot the extent of the patient's visual field, as well ... The extent of the visual field is mapped to targets of different sizes and brightness. The results of this method are plotted ... Automated perimetry involves systematically quantifying a patient's visual field by showing to an illuminated target against a ...
Community Eye Health Journal » Visual field testing for glaucoma - a practical guideThis article focuses on some of the more practical aspects of visual field testing, with an emphasis on assessing glaucoma. ... Examining visual fields is an integral part of a full ophthalmic evaluation. ... Figure 2. A normal visual field (left eye) © ICEH Part 2 Features of glaucomatous visual field defects. Visual field loss can ... Loss of visual acuity can be very disabling, but so too can extensive loss of peripheral visual field. Loss of visual field, ...
Loss of vision in one half of the visual field, Tingling, Weakness of limb: 1 Possible CausesDiscover 1 possible causes for loss of vision in one half of the visual field, tingling, weakness of limb including Stroke ...
Can brain lesion cause peripheral vision loss - Answers on HealthTapDifferent locations of brain lesions cause different patterns of visual field loss that can be detected through formal testing. ... A visual field is performed to detect the amount of binocular horizontal visual field. For example, some rules require it to be ... Yes, but: The patient needs to have a visual field test to determine how much field loss there is. Sometimes, there is so much ... Visual field test result normal - 3/14 fixation error. Some peripheral vision loss not in field of vision. Why does test result ...
Bulbs - Perimeter Visual FieldOphthalmic Supply; Perimeter Visual Field Bulbs. Home , Ophthalmic Supply , Supply: Bulbs , Perimeter Visual Field Bulbs ...
An Evidence-Based Review of Prognostic Factors for Glaucomatous Visual Field Progression.DESIGN: Knowledge of prognostic factors helps clinicians to select patients at risk of glaucomatous visual field progression ... To examine which prognostic factors are associated with glaucomatous visual field progression. ... DESIGN: Knowledge of prognostic factors helps clinicians to select patients at risk of glaucomatous visual field progression ... The following factors were clearly associated with glaucomatous visual field progression: age, disc hemorrhages (for NTG), ...
Dataset Properties Dialog Box, FieldsField Source Enter a value for the field. For a calculated field, the field source must be the name of an existing field ... Delete the selected field from the dataset. Field Name. Type a name for the field. The field must be unique within the dataset ... Select Fields on the Dataset Properties dialog box to change the field collection for the report dataset. The fields list is ... For a query field, the field source must be the name of an existing field retrieved by the dataset query. ...
Headache, Loss of vision in one half of the visual field, Visual impairment: 4 Possible Causes... visual impairment including Stroke Overview, Subarachnoid Hemorrhage and Everything You Want to Know About Migraine ... loss of vision in one half of the visual field, ... Loss Of Vision In One Half Of The Visual Field, and Visual ...
Visual Field Testing | Heights Eyecare in Billings MTVisual field testing aids us in preventing vision loss from diseases like glaucoma ... Visual Field Testing. October 14, 2014. EducationHeights Eyecare Heights EyeCare is dedicated to ocular disease diagnosis and ... This visual field testing will be another valuable tool to aid us in intervening as early as possible with a treatment to ... The Humphrey Field Analyzer with its advanced software enables the doctors to diagnose diseases resulting in field loss. ...
New & Used Visual Field Analyzer | Buy Used Visual Field Analyzer EquipmentFind any required new, refurbished or used Visual Field Analyzer Equipment or device. ... used Visual Field Analyzer Equipment for sale or auction. ... Visual Field Analyzer may also be referred to as : Visual Field ...
"THE EFFECT OF SIMULTANEOUS, IRRELEVANT AUDITORY AND VISUAL STIMULI ON " by Keri Davis... that an irrelevant visual stimulus affects auditory attention more so in the left visual field than the right visual field. ... This study was designed to study the effect of an irrelevant visual stimulus and an auditory distraction of backward speech on ... I predicted that the visual stimulus and backward speech would not have a significant effect on the ear advantage. The results ... showed that all subjects were able to force their attention to the ear regardless of the visual or auditory distracters. In ...
Visual Field TestingGoldmann visual fields and automated visual fields. The standard type of visual field test is called automated static Perimetry ... If the visual field test shows vision loss in a characteristic pattern, it can help the eye doctor diagnose the cause of the ... Visual field testing can catch vision changes early in the process before significant vision loss occurs and is considered one ... A visual field test, also called Perimetry, measures the sensitivity of a person's central and peripheral vision. There are ...
The Performance Artist of Memory. - Michael ChorostI could see both it and most of my visual field at the same time. ... taking care to hold the processor in his field of view, and ... But Thad has 15 years of notes at hand and Google constantly in his field of view. If he sees someone he met five years ago, he ...
12/09 - 12/16... by plotting the visual fields.. It is expected that some parts of the visual fields are lost from retinal diseases such as POAG ... By examining the visual fields, the location of the lesions becomes apparent. The real question is then what the nature of the ... Occasionally, a patient comes in complaining of severe headaches and, at the same time, part of his/her visual field is missing ... The angle and the optic disc can both be imaged with OCT (Optic Coherence Tomography). And the visual fields plotted with ...
MedicineNet Visual Field Test Specialtyhttp://www.medicinenet.com/visual_field_test/index.htm. MedicineNet Visual Field Test Specialty. en-us. Copyright 1995-2017 ...
Pages that link to "Divided visual field paradigm" - WikipediaPages that link to "Divided visual field paradigm". ← Divided visual field paradigm ... Talk:Divided visual field paradigm (links , edit). *Wikipedia talk:WikiProject Articles for creation/G13 rescue (links , ... File:Diagram of lateralized visual pathways of the human brain.png (links , edit) ... Retrieved from "https://en.wikipedia.org/wiki/Special:WhatLinksHere/Divided_visual_field_paradigm" ...
Best 25+ ideas about Visual Field | Find what you'll loveDiscover and save today's best ideas about Visual Field on Bing feed. Updated daily with the best images from around the web. ... Discover and save today's best ideas about Visual Field on Bing feed. Updated daily with the best images from around the web. ... Visual Field Pathway Defects. *What type of visual field defect would be caused … ... Visual Field Defects. *Here are the visual fields test results of our patien… ...
Visual Field Testing for Glaucoma and Other Eye ProblemsVisual field tests can detect central and peripheral vision problems caused by glaucoma, stroke and other eye or brain problems ... Types of Visual Field Tests. Confrontation visual field testing typically is used as a screening visual field test. One eye is ... These "baseline" visual field test results can then be used to assess potential changes in your visual field in the future. ... Visual field tests are performed by eye care professionals to detect blind spots (scotomas) and other visual field defects, ...
Computerized visual fields: what they are and how to use them - William R. Whalen - Google Books... threshold values tion vision visual acuity visual field defects visual field examination Visual Field Symposium visual field ... Visual Field Testing with the Humphrey Field Analyzer: A Text and Clinical Atlas. Neil T. Choplin,Russell P. Edwards. Snippet ... fields.html?id=yFl8AAAAIAAJ&utm_source=gb-gplus-shareComputerized visual fields. ... Computerized visual fields: what they are and how to use them. William R. Whalen. Snippet view - 1985. ...
Headache, Loss of vision in one half of the visual field, Nausea: 4 Possible Causes... loss of vision in one half of the visual field, nausea including Everything You Want to Know About Migraine, Subarachnoid ...
"There's Something in Your Eye: Ethical Implications of Augmented Visual Field Devices" by Marty J....This paper aims to explore the ethical and social impact of augmented visual field devices (AVFDs), identifying issues that ... This paper aims to explore the ethical and social impact of augmented visual field devices (AVFDs), identifying issues that ... There's Something in Your Eye: Ethical Implications of Augmented Visual Field Devices ... ethical implications of augmented visual field devices. Journal of Information, Communication and Ethics in Society, 14(3), 214 ...
DNA Clean-Up BuffersCapturem His-Tagged Purification Maxiprep Visual Protocol * Denaturing Purification with TALON Resin Protocol-At-A-Glance ... In-Fusion Field Tester Terms & Conditions * DNA Ligation Kits * DNA Ligation Kit for Long Fragments ...
BASEBALL PITCH QUALITY DETERMINATION METHOD AND APPARATUS - GREINER AGENCIES, INC.The pitch rating device 450 includes a plurality of cameras 455a, 455b, 455c acquiring video data of the baseball field. The ... For example, the display 110 can be configured to show the path of the pitch, the values or visual indications of the values of ... In some embodiments, the radar gun 500 can be calibrated based on markers within the field of view of the radar gun (e.g., a ... The Doppler radar detector 405 can be configured to identify the ball among the various objects and people on the field, track ...
Disingenuous Media ReactionThis *can* be tampered with and quite easily, so getting images from the field to an archival site *without* intervening data ... Visual Interactive Syntax Learning - Danish-English Online Translator. *Food From Poland, LLC ...
Meridian (perimetry, visual field): Meridian (plural: "meridians") is used in perimetry and in specifying visual fields. According to IPS Perimetry Standards 1978 (2002): "Perimetry is the measurement of [an observer's] visual functions ...Plaque-forming unit: In virology, a plaque-forming unit (PFU) is a measure of the number of particles capable of forming plaques per unit volume, such as virus particles. It is a functional measurement rather than a measurement of the absolute quantity of particles: viral particles that are defective or which fail to infect their target cell will not produce a plaque and thus will not be counted.Operation Eyesight Universal: Operation Eyesight Universal is a Canada-based international development organisation, founded in 1963. It works to prevent avoidable blindness and to cure blindness that is treatable.LogMAR chart: A LogMAR chart comprises rows of letters and is used by ophthalmologists and vision scientists to estimate visual acuity. This chart was developed at the National Vision Research Institute of Australia in 1976, and is designed to enable a more accurate estimate of acuity as compared to other charts (e.Homonymous hemianopsiaScotomaCharles D. Phelps: Charles Dexter Phelps (September 16, 1937 – September 13, 1985) was a prominent American medical doctor, professor, and researcher in the field of ophthalmology. The clinical studies he oversaw contributed to significant advances in the scientific understanding and surgical and pharmacological treatment of glaucoma.LevobetaxololLandolt COptic disc: The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. BecauseIntraocular pressurePercolation threshold: Percolation threshold is a mathematical concept related to percolation theory, which is the formation of long-range connectivity in random systems. Below the threshold a giant connected component does not exist; while above it, there exists a giant component of the order of system size.Binocular vision: Binocular vision is vision in which creatures having two eyes use them together. The word binocular comes from two Latin roots, bini for double, and oculus for eye.Biological motion: Biological motion is a term used by social and cognitive neuroscientists to refer to the unique visual phenomenon of a moving, animate object. Often, the stimuli used in biological motion experiments are just a few moving dots that reflect the motion of some key joints of the moving organism.Gary H. Posner: Gary H. Posner (born c.Sensory decussation: The sensory decussation or decussation of the lemniscus is a decussation or crossover of axons from the gracile nucleus and cuneate nucleus, which are responsible for fine touch, proprioception and two-point discrimination of the body. The fibres of this decussation are called the internal arcuate fibres and are found at the superior aspect of the closed medulla superior to the motor decussation.VigabatrinRetinal regeneration: Retinal regeneration deals with restoring retinal function to vertebrates so impaired.Korte's law: In psychophysics, Korte's law, also known more completely as Korte's third law of apparent motion, is an observation relating the phenomenon of apparent motion to the distance and duration between two successively presented stimuli. It was originally proposed in 1915 by Adolf Korte.Blind People's Association: The Blind People’s Association (BPA) is an organisation in India which promotes comprehensive rehabilitation of persons with all categories of disabilities through education, training, employment, community based rehabilitation, integrated education, research, publications, human resource development and other innovative means.Coherence theory: In physics, coherence theory is the study of optical effects arising from partially coherent light and radio sources. Partially coherent sources are sources where the coherence time or coherence length are limited by bandwidth, by thermal noise, or by other effect.Macula of retina: The macula or macula lutea (from Latin macula, "spot" + lutea, "yellow") is an oval-shaped pigmented area near the center of the retina of the human eye. It has a diameter of around .Neuropathy, ataxia, and retinitis pigmentosaCerebral hemisphere: The vertebrate cerebrum (brain) is formed by two cerebral hemispheres that are separated by a groove, the medial longitudinal fissure. The brain can thus be described as being divided into left and right cerebral hemispheres.Nerve fiber layer: The retinal nerve fiber layer (nerve fiber layer, stratum opticum, RNFL) is formed by the expansion of the fibers of the optic nerve; it is thickest near the porus opticus, gradually diminishing toward the ora serrata.Electromagnetic environment: In telecommunication, the term electromagnetic environment (EME) has the following meanings:Low vision assessment: Low vision is both a subspeciality and a condition. Optometrists and Ophthalmologists after their training may undergo further training in Low vision assessment and management.HyperintensityOptic neuropathySaccade: A saccade ( , French for jerk) is quick, simultaneous movement of both eyes between two phases of fixation in the same direction.Cassin, B.Scanning laser ophthalmoscopyImbert-Fick law: The Imbert-Fick "law" was invented by Hans Goldmann (1899–1991) to give his newly marketed tonometer (with the help of the Haag-Streit Company) a quasi-scientific basis; it is mentioned in the ophthalmic and optometric literature, but not in any books of physics. According to Goldmann,Goldmann H.Hemispatial neglectPurtscher's retinopathy: Purtscher's retinopathy is a disease where part of the eye (retina) is damaged. Usually associated with severe head injuries, it may also occur with other types of trauma, such as long bone fractures, or with several non-traumatic systemic diseases.Cue stick: A cue stick (or simply cue, more specifically pool cue, snooker cue, or billiards cue), is an item of sporting equipment essential to the games of pool, snooker and carom billiards. It is used to strike a ball, usually the .Tadpole pupil: The eye is made up of the sclera, the iris, and the pupil, a black hole located at the center of the eye with the main function of allowing light to pass to the retina. Due to certain muscle spasms in the eye, the pupil can resemble a tadpole, which consists of a circular body, no arms or legs, and a tail.Rimless eyeglasses: Rimless eyeglasses, are a type of eyeglasses in which the lenses are mounted directly to the bridge and/or temples. The style is divided into two subtypes: three piece glasses are composed of lenses mounted to a bridge and two separate temple arms, while rimways (also called cortlands) feature a supporting arch that connects the temples to the bridge and provides extra stability for the lenses.Fixation reflex: The fixation reflex is that concerned with attracting the eye on a peripheral object. For example, when a light shines in the periphery, the eyes shift gaze on it.Cortical blindnessCanon EOS 5Amorphosynthesis: Amorphosynthesis is a medical condition where the patient is unaware of somatic sensations from one side of the body; the left side is most commonly affected. This condition is usually a sign of a lesion in the right parietal lobe.Outline of photography: The following outline is provided as an overview of and topical guide to photography:Optic nerve tumor: An optic nerve melanocytoma is a tumor made up of melanocytes and melanin. These tumors are typically a benign; they can grow, but rarely transform into a malignancy.Electrical impedance tomography: Electrical Impedance Tomography (EIT) is a non-invasive medical imaging technique in which an image of the conductivity or permittivity of part of the body is inferred from surface electrode measurements. Electrical conductivity depends on free ion content and differs considerably between various biological tissues (absolute EIT) or different functional states of one and the same tissue or organ (relative or functional EIT).Flicker (screen): Flicker is a visible fading between cycles displayed on video displays, especially the refresh interval on cathode ray tube (CRT) based computer screens. Flicker occurs on CRTs when they are driven at a low refresh rate, allowing the brightness to drop for time intervals sufficiently long to be noticed by a human eye – see persistence of vision and flicker fusion threshold.Spalding MethodGlare (vision): Glare is difficulty seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. Because of this, some cars include mirrors with automatic anti-glare functions.PapilledemaMagnetic pulse welding: Magnetic pulse welding (MPW) is a solid state welding process that uses magnetic forces to weld two workpieces together. The welding mechanism is most similar to that of explosion welding.Generalizability theory: Generalizability theory, or G Theory, is a statistical framework for conceptualizing, investigating, and designing reliable observations. It is used to determine the reliability (i.Autorefractor: An autorefractor or automated refractor is a computer-controlled machine used during an eye examination to provide an objective measurement of a person's refractive error and prescription for glasses or contact lenses. This is achieved by measuring how light is changed as it enters a person's eye.Temporal analysis of products: Temporal Analysis of Products (TAP), (TAP-2), (TAP-3) is an experimental technique for studyingCats in the United States: Many different species of mammal can be classified as cats (felids) in the United States. These include domestic cat (both house cats and feral), of the species Felis catus; medium-sized wild cats from the genus Lynx; and big cats from the genera Puma and Panthera.Optic neuritisAmblyopiaGene therapy for color blindness: Gene therapy for color blindness is an experimental gene therapy aiming to convert congenitally colorblind individuals to trichromats by introducing a photopigment gene that they lack. Though partial color blindness is considered only a mild disability and is controversial whether it is even a disorder, it is a condition that affects many people, particularly males.Tema Motorway: The Tema Motorway is a highway that links Tema to Accra—capital of Ghana. It was the only motorway in Ghana.Flashlight: A flashlight or torch in British English, is a portable hand-held electric light. Usually, the source of the light is a small incandescent light bulb or light-emitting diode (LED).HSD2 neurons: HSD2 neurons are a small group of neurons in the brainstem which are uniquely sensitive to the mineralocorticosteroid hormone aldosterone, through expression of HSD11B2. They are located within the caudal medulla oblongata, in the nucleus of the solitary tract (NTS).Assay sensitivity: Assay sensitivity is a property of a clinical trial defined as the ability of a trial to distinguish an effective treatment from a less effective or ineffective intervention. Without assay sensitivity, a trial is not internally valid and is not capable of comparing the efficacy of two interventions.Tumor progression: Tumor progression is the third and last phase in tumor development. This phase is characterised by increased growth speed and invasiveness of the tumor cells.Image fusion: In computer vision, Multisensor Image fusion is the process of combining relevant information from two or more images into a single image.Haghighat, M.Stereopsis: Stereopsis (from the Greek στερεο- [meaning "solid", and ὄψις] opsis, "appearance, [[visual perception|sight") is a term that is most often used to refer to the perception of depth and 3-dimensional structure obtained on the basis of visual information deriving from two eyes by individuals with normally developed binocular vision.
(1/4118) On the neural correlates of visual perception.
Neurological findings suggest that the human striate cortex (V1) is an indispensable component of a neural substratum subserving static achromatic form perception in its own right and not simply as a central distributor of retinally derived information to extrastriate visual areas. This view is further supported by physiological evidence in primates that the finest-grained conjoined representation of spatial detail and retinotopic localization that underlies phenomenal visual experience for local brightness discriminations is selectively represented at cortical levels by the activity of certain neurons in V1. However, at first glance, support for these ideas would appear to be undermined by incontrovertible neurological evidence (visual hemineglect and the simultanagnosias) and recent psychophysical results on 'crowding' that confirm that activation of neurons in V1 may, at times, be insufficient to generate a percept. Moreover, a recent proposal suggests that neural correlates of visual awareness must project directly to those in executive space, thus automatically excluding V1 from a related perceptual space because V1 lacks such direct projections. Both sets of concerns are, however, resolved within the context of adaptive resonance theories. Recursive loops, linking the dorsal lateral geniculate nucleus (LGN) through successive cortical visual areas to the temporal lobe by means of a series of ascending and descending pathways, provide a neuronal substratum at each level within a modular framework for mutually consistent descriptions of sensory data. At steady state, such networks obviate the necessity that neural correlates of visual experience project directly to those in executive space because a neural phenomenal perceptual space subserving form vision is continuously updated by information from an object recognition space equivalent to that destined to reach executive space. Within this framework, activity in V1 may engender percepts that accompany figure-ground segregations only when dynamic incongruities are resolved both within and between ascending and descending streams. Synchronous neuronal activity on a short timescale within and across cortical areas, proposed and sometimes observed as perceptual correlates, may also serve as a marker that a steady state has been achieved, which, in turn, may be a requirement for the longer time constants that accompany the emergence and stability of perceptual states compared to the faster dynamics of adapting networks and the still faster dynamics of individual action potentials. Finally, the same consensus of neuronal activity across ascending and descending pathways linking multiple cortical areas that in anatomic sequence subserve phenomenal visual experiences and object recognition may underlie the normal unity of conscious experience. (+info)
(2/4118) Transient and permanent deficits in motion perception after lesions of cortical areas MT and MST in the macaque monkey.
We examined the nature and the selectivity of the motion deficits produced by lesions of extrastriate areas MT and MST. Lesions were made by injecting ibotenic acid into the representation of the left visual field in two macaque monkeys. The monkeys discriminated two stimuli that differed either in stimulus direction or orientation. Direction and orientation discrimination were assessed by measuring thresholds with gratings and random-dots placed in the intact or lesioned visual fields. At the start of behavioral testing, we found pronounced, motion-specific deficits in thresholds for all types of moving stimuli, including pronounced elevations in contrast thresholds and in signal-to-noise thresholds measured with moving gratings, as well as deficits in direction range thresholds and motion coherence measured with random-dot stimuli. In addition, the accuracy of direction discrimination was reduced at smaller spatial displacements (i.e. step sizes), suggesting an increase in spatial scale of the residual directional mechanism. Subsequent improvements in thresholds were seen with all motion stimuli, as behavioral training progressed, and these improvements occurred only with extensive behavioral testing in the lesioned visual field. These improvements were particularly pronounced for stimuli not masked by noise. On the other hand, deficits in the ability to extract motion from noisy stimuli and in the accuracy of direction discrimination persisted despite extensive behavioral training. These results demonstrate the importance of areas MT and MST for the perception of motion direction, particularly in the presence of noise. In addition, they provide evidence for the importance of behavioral training for functional recovery after cortical lesions. The data also strongly support the idea of functional specialization of areas MT and MST for motion processing. (+info)
(3/4118) Retinotopic mapping of lateral geniculate nucleus in humans using functional magnetic resonance imaging.
Subcortical nuclei in the thalamus, which play an important role in many functions of the human brain, provide challenging targets for functional mapping with neuroimaging techniques because of their small sizes and deep locations. In this study, we explore the capability of high-resolution functional magnetic resonance imaging at 4 Tesla for mapping the retinotopic organization in the lateral geniculate nucleus (LGN). Our results show that the hemifield visual stimulation only activates LGN in the contralateral hemisphere, and the lower-field and upper-field visual stimulations activate the superior and inferior portion of LGN, respectively. These results reveal a similar retinotopic organization between the human and nonhuman primate LGN and between LGN and the primary visual cortex. We conclude that high-resolution functional magnetic resonance imaging is capable of functional mapping of suborganizations in small nuclei together with cortical activation. This will have an impact for studying the thalamocortical networks in the human brain. (+info)
(4/4118) Early visual experience shapes the representation of auditory space in the forebrain gaze fields of the barn owl.
Auditory spatial information is processed in parallel forebrain and midbrain pathways. Sensory experience early in life has been shown to exert a powerful influence on the representation of auditory space in the midbrain space-processing pathway. The goal of this study was to determine whether early experience also shapes the representation of auditory space in the forebrain. Owls were raised wearing prismatic spectacles that shifted the visual field in the horizontal plane. This manipulation altered the relationship between interaural time differences (ITDs), the principal cue used for azimuthal localization, and locations of auditory stimuli in the visual field. Extracellular recordings were used to characterize ITD tuning in the auditory archistriatum (AAr), a subdivision of the forebrain gaze fields, in normal and prism-reared owls. Prism rearing altered the representation of ITD in the AAr. In prism-reared owls, unit tuning for ITD was shifted in the adaptive direction, according to the direction of the optical displacement imposed by the spectacles. Changes in ITD tuning involved the acquisition of unit responses to adaptive ITD values and, to a lesser extent, the elimination of responses to nonadaptive (previously normal) ITD values. Shifts in ITD tuning in the AAr were similar to shifts in ITD tuning observed in the optic tectum of the same owls. This experience-based adjustment of binaural tuning in the AAr helps to maintain mutual registry between the forebrain and midbrain representations of auditory space and may help to ensure consistent behavioral responses to auditory stimuli. (+info)
(5/4118) Test-retest variability of frequency-doubling perimetry and conventional perimetry in glaucoma patients and normal subjects.
PURPOSE: To compare the test-retest variability characteristics of frequency-doubling perimetry, a new perimetric test, with those of conventional perimetry in glaucoma patients and normal control subjects. METHODS: The study sample contained 64 patients and 47 normal subjects aged 66.16+/-11.86 and 64.26+/-7.99 years (mean +/- SD), respectively. All subjects underwent frequency-doubling perimetry (using the threshold mode) and conventional perimetry (using program 30-2 of the Humphrey Field Analyzer; Humphrey Instruments, San Leandro, CA) in one randomly selected eye. Each test was repeated at 1-week intervals for five tests with each technique over 4 weeks. Empirical 5th and 95th percentiles of the distribution of threshold deviations at retest were determined for all combinations of single tests and mean of two tests, stratified by threshold deviation. The influence of visual field eccentricity and overall visual field loss on variability also were examined. RESULTS: Mean test time with frequency-doubling perimetry in patients and normal control subjects was 5.90 and 5.25 minutes, respectively, and with conventional perimetry was 17.20 and 14.01 minutes, respectively. In patients, there was a significant correlation between the results of the two techniques, in the full field and in quadrants, whereas in normal subjects there was no such correlation. In patients, the retest variability of conventional perimetry in locations with 20-dB loss was 120% (single tests) and 127% (mean tests) higher compared with that in locations with 0-dB loss. Comparative figures for frequency-doubling perimetry were 40% and 47%, respectively. Variability also increased more with threshold deviation in normal subjects tested with conventional perimetry. In both patients and normal subjects, variability increased with visual field eccentricity in conventional perimetry, but not in frequency-doubling perimetry. Both techniques showed an increase in variability with overall visual field damage. CONCLUSIONS: Frequency-doubling perimetry has different test-retest variability characteristics than conventional perimetry and may have potential for monitoring glaucomatous field damage. (+info)
(6/4118) Selective horizontal dysmetropsia following prestriate lesion.
We describe a patient (P.S.) who, following a right prestriate lesion, reported that objects in the left visual field appeared distorted and smaller than those on the right. Other aspects of visual processing were remarkably unaffected. We carried out a series of size comparison tests using simple or complex stimuli and requiring different types of behavioural responses. We found that P.S. significantly underestimated the size of stimuli presented in her left visual field. When comparison tasks involved stimuli placed along the vertical axis or in the right visual field, P.S. performed well. The vertical and horizontal components of size distortion were found to be differentially affected. We conclude that size processing may be dissociated from other aspects of visual processing, such as form or colour processing, and depends critically on part of the occipital, prestriate areas (Brodmann areas 18-19). (+info)
(7/4118) Evaluation of focal defects of the nerve fiber layer using optical coherence tomography.
OBJECTIVE: To analyze glaucomatous eyes with known focal defects of the nerve fiber layer (NFL), relating optical coherence tomography (OCT) findings to clinical examination, NFL and stereoscopic optic nerve head (ONH) photography, and Humphrey 24-2 visual fields. DESIGN: Cross-sectional prevalence study. PARTICIPANTS: The authors followed 19 patients in the study group and 14 patients in the control group. INTERVENTION: Imaging with OCT was performed circumferentially around the ONH with a circle diameter of 3.4 mm using an internal fixation technique. One hundred OCT scan points taken within 2.5 seconds were analyzed. MAIN OUTCOME MEASURES: Measurements of NFL thickness using OCT were performed. RESULTS: In most eyes with focal NFL defects, OCTs showed significant thinning of the NFL in areas closely corresponding to focal defects visible on clinical examination, to red-free photographs, and to defects on the Humphrey visual fields. Optical coherence tomography enabled the detection of focal defects in the NFL with a sensitivity of 65% and a specificity of 81%. CONCLUSION: Analysis of NFL thickness in eyes with focal defects showed good structural and functional correlation with clinical parameters. Optical coherence tomography contributes to the identification of focal defects in the NFL that occur in early stages of glaucoma. (+info)
(8/4118) Cross-correlation study of the temporal interactions between areas V1 and V2 of the macaque monkey.
Cross-correlation studies performed in cat visual cortex have shown that neurons in different cortical areas of the same hemisphere or in corresponding areas of opposite hemispheres tend to synchronize their activities. The presence of synchronization may be related to the parallel organization of the cat visual system, in which different cortical areas can be activated in parallel from the lateral geniculate nucleus. We wanted to determine whether interareal synchronization of firing can also be observed in the monkey, in which cortical areas are thought to be organized in a hierarchy spanning different levels. Cross-correlation histograms (CCHs) were calculated from pairs of single or pairs of multiunit activities simultaneously recorded in areas V1 and V2 of paralyzed and anesthetized macaque monkeys. Moving bars and flashed bars were used as stimuli. The shift predictor was calculated and subtracted from the raw CCH to reveal interactions of neuronal origin in isolation. Significant CCH peaks, indicating interactions of neuronal origin, were obtained in 11% of the dual single-unit recordings and 46% of the dual multiunit recordings with moving bars. The incidence of nonflat CCHs with flashed bars was 29 and 78%, respectively. For the pairs of recording sites where both flashed and moving stimuli were used, the incidences of significant CCHs were very similar. Three types of peaks were distinguished on the basis of their width at half-height: T (<16 ms), C (between 16 and 180 ms), and H peaks (>180 ms). T peaks were very rarely observed (<1% in single-unit recordings). H peaks were observed in 7-16% of the single-unit CCHs, and C peaks in 6-16%, depending on the stimulus used. C and H peaks were observed more often when the receptive fields were overlapping or distant by <2 degrees. To test for the presence of synchronization between neurons in areas V1 and V2, we measured the position of the CCH peak with respect to the origin of the time axis of the CCH. Only in the case of a few T peaks did we find displaced peaks, indicating a possible drive of the V2 neuron by the simultaneously recorded V1 cell. All the other peaks were either centered on the origin or overlapped the origin of time with their upper halves. Thus similarly to what has been reported for the cat, neurons belonging to different cortical areas in the monkey tend to synchronize the time of emission of their action potentials with three different levels of temporal precision. For peaks calculated from flashed stimuli, we compared the peak position with the difference between latencies of V1 and V2 neurons. There was a clear correlation for single-unit pairs in the case of C peaks. Thus the position of a C peak on the time axis appears to reflect the order of visual activation of the correlated neurons. The coupling strength for H peaks was smaller during visual drive compared with spontaneous activity. On the contrary, C peaks were seen more often and were stronger during visual stimulation than during spontaneous activity. This suggests that C-type synchronization is associated with the processing of visual information. The origin of synchronized activity in a serially organized system is discussed. (+info)
open angle gl
- Central corneal thickness as a predictor of visual field loss in primary open angle glaucoma for a Hispanic population. (biomedsearch.com)
- PURPOSE: To evaluate whether the central corneal thickness correlates inversely with the severity of visual field loss in Primary Open Angle Glaucoma. (biomedsearch.com)
- RESULTS: Patients with Primary Open Angle Glaucoma show a statistically significant inverse correlation between central corneal thickness and the severity of the visual field damage. (biomedsearch.com)
- CONCLUSION: Thinner corneas could be considered a risk factor for the severity of visual field loss in Primary Open Angle Glaucoma. (biomedsearch.com)
- METHODS: By consulting relevant databases, we identified 2733 articles published up to September 2010, of which 85 articles investigating prognostic factors for visual field progression in patients with open-angle glaucoma (OAG) were eligible. (biomedsearch.com)
- In people with ocular hypertension, the optic nerve appears normal and no signs of glaucoma are found during visual field testing, which tests side (peripheral) vision. (iblogalot.com)
- Visual field testing can catch vision changes early in the process before significant vision loss occurs and is considered one of the main tests to monitor the visual status in glaucoma patients. (blogspot.com)
- Hemianopsia is the loss of half of the visual field. (rmchealth.com)
- A person with hemianopsia only sees a portion of the visual field from each eye. (rmchealth.com)
- Altitudinal hemianopsia involving the upper visual field of one eye and the lower visual field of the other. (dictionary.com)
- A visual field test, also called Perimetry, measures the sensitivity of a person's central and peripheral vision. (blogspot.com)
- The standard type of visual field test is called automated static Perimetry. (blogspot.com)
- Identifying risk factors for the development of moderate to severe visual field loss may decrease the proportion of patients that experience the severe forms of this disease. (biomedsearch.com)
- The following factors were clearly associated with glaucomatous visual field progression: age, disc hemorrhages (for NTG), baseline visual field loss, baseline intraocular pressure (IOP), and exfoliation syndrome. (biomedsearch.com)
- If the visual field test shows vision loss in a characteristic pattern, it can help the eye doctor diagnose the cause of the problem. (blogspot.com)
- This can be done with a visual field test that makes a map of your field of vision. (rmchealth.com)
- DESIGN: Knowledge of prognostic factors helps clinicians to select patients at risk of glaucomatous visual field progression and intensify their treatment. (biomedsearch.com)
- Your field of vision will be tested. (rmchealth.com)
- It shifts the location of an image so that it is within your field of vision. (rmchealth.com)
- This will help you capture things outside your field of vision. (rmchealth.com)
- This will prevent you from bumping into objects outside of your field of vision. (rmchealth.com)
- That way, more of the action will be within your field of vision. (rmchealth.com)
- If you are having problems with your vision, or would like more information on visual field testing, contact D'Ambrosio Eye Care at 800-325-3937. (blogspot.com)