- Visual Fields via the Visual Pathway - CRC Press Book
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- Disorders of the visual pathway
Visual Fields via the Visual Pathway - CRC Press Book
Notice that the central visual field for the left eye is represented by a black spot, indicating a loss of central field vision. Symptoms: The patient complains of a sudden headache and loss of vision in his left eye. Ophthalmoscope examination does not reveal abnormalities in the left eye 1. However, confrontation testing indicates a severe loss of vision in the left eye. The patient is referred for immediate neuroradiographic tests and perimetry testing. Perimetry Test Results: The results indicate the right eye's visual field is normal and that there is a large visual loss encompassing nearly all of the left eye's visual field Figure Neural imaging results indicate an aneurysm on the left ophthalmic artery, which is compressing the left optic nerve Figure Compression of the nerve prevents action potentials from the retina to travel to the lateral geniculate nucleus of the thalamus.
Long-term compression may damage the nerve, however, of greater concern is the potential rupture of the aneurysm, which could cause extensive brain damage. Optic Nerve Damage: Each optic nerve contains the axons of retinal ganglion cells from one eye, e. Damage to one optic nerve will produce a monocular visual field defect.
Destruction of one optic nerve e.
Notice that only the temporal halves of the two central areas exhibit a visual loss i. Symptoms: At his annual physical exam, the patient complains of a general malaise and changes in his vision that he noticed while playing soccer.
He said he was often "blindsided" on the playing field because he "couldn't see players approaching him from the side". Ophthalmoscope examination does not reveal abnormalities in either eye 2. Confrontation field testing indicates a constriction of the temporal hemifields of both eyes. The patient is referred for neuroradiographic tests and perimetry testing. Perimetry Test Results: The results indicate a bitemporal hemianopia , i.
Neural imaging results Figure Compression of the decussating nerve fibers prevents action potentials from the nasal hemiretina to reach the contralateral lateral geniculate nucleus of the thalamus. As the tumor grows larger it will crush the optic chiasm, destroying it and eventually compromising the remaining optic nerve fibers.
Optic Chiasm Damage: The fibers of the optic nerve that originate from ganglion cells in the nasal half of the retina decussate in the optic chiasm to the opposite optic tract Figure The crossing fibers of the optic chiasm may be crushed by a pituitary tumor. Damage to the optic chiasm produces a unique form of visual field deficit, a bitemporal hemianopia Figure Recall that the fibers of the optic chiasm carry information about objects in the temporal hemifields of both eyes i.
Consequently section of the optic chiasm produces a visual loss in only the temporal half of the visual field of each eye. When the patient views the world out of both eyes, the boundary of his binocular visual field is narrower than normal. Symptoms: A patient is brought to the emergency room complaining of a severe headache and nausea.
He is conscious and coherent when examined in the ER. Ophthalmoscope examination does not reveal abnormalities in either eye. Confrontation field testing indicates a visual loss in the right hemifield of both eyes. Perimetry Test Results: The results indicate a right homonymous hemianopia with macular sparing Figure Neural imaging results indicate injury to the rostral half of the left calcarine cortex, which receives blood from the left posterior cerebral artery Figure Recall that the rostral calcarine cortex processes information from the visual field periphery, whereas the caudal and lateral striate cortex process information derived from the visual field center.
The medial and inferior portions of the occipital lobe receives blood from branches of the posterior cerebral artery. Calcarine Cortex Damage. An infarct created by obstruction of, or a hemorrhage in, branches of the posterior cerebral artery may result in damage to the rostral calcarine cortex. Damage to the calcarine cortex on one side may produce a binocular, contralateral homonymous hemianopia with macular sparing Figure A collateral blood supply from branches of the middle cerebral artery is believed to spare the cortical neurons in the caudal and lateral regions of the striate cortex, which receive information from the macular area.
Distribution of the major branches of the anterior and posterior cerebral arteries viewed on the inferior and medial surfaces of the brain with the cerebellum removed B. The location of the lesion is colored red.
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Symptoms: A patient, who is stabilized after suffering a stroke two months earlier, is referred to a neuro-ophthalmologist for evaluation. The patient does not appear to be blind but has problems with processing visual information.
For example, the patient cannot describe the color of an object presented to him or recognize faces. He has normal spatial orientation and motion detection. Perimetry Test Results: The results indicate no consistent loss of vision.
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However, it is difficult to obtain consistent results because the patient tires easily and his attention appears to wander. Neural imaging results indicate damage to the caudal portion of the inferior temporal lobe, which normally receives blood from branches of the posterior cerebral artery. Extrastriate or Association Cortex Damage: While destruction of the primary visual cortex produces blindness in the contralesional hemifield, damage to cortical areas surrounding the striate cortex does not Instead, they may produce profound deficits in the higher order-processing of visual information.
For example, bilateral damage to a small area of the inferior temporal gyrus Figure Damage to more superior areas of the temporal lobe area 39 in Figure Damage to areas in the parietal cortex may result in the inability to see motion i. The object does not appear to move; rather it appears to have jumped from one place to the next.
Damage to large areas involving the posterior parietal cortex and superior temporal cortex may result in the symptom of "neglect", wherein objects in parts of the visual field are ignored or denied existence. Chapters include numerous illustrations of visual field results, colour plates of associated fundus images, and neuroimaging scans. References and further reading lists are also provided with key articles and up-to-date literature.
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Disorders of the visual pathway
Delivery And Returns. All orders will be delivered by An Post. As a clinical practitioner, researcher and educator, Fiona Rowe has actively investigated and interpreted visual fields from all aspects of ocular pathology over the last 15 years. She is regularly invited to present to professional groups on this topic. This textbook is a dynamic exploration of the relationship between the visual pathway and visual field impairments. Aimed at the practitioner or student of visual fields, the clinical focus of the book is oriented towards differential diagnosis and will assist the reader in identifying the site of a lesion.
The emphasis is on detection and interpretation of visual field defects, rather than the background and psychophysics of visual field assessment. Discussion of the normal visual field is included for comparative purposes.