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The Visual Pathway and Related Disorders

The primary visual pathway consists of a relay system, beginning at the retina, whose ganglion cell axons form the optic nerve. The optic nerve fibers from each eye hemidecussate in the optic chiasm (OC), with nasal fibers joining the temporal fibers of the contralateral nerve. The nasal fibers continue as the optic tract on each side, synapsing with the lateral geniculate nucleus (LGN) of the thalamus. Signals are then transmitted to the primary visual cortex of the occipital lobe. The right and left visual fields are processed by opposite hemispheres. Lesions along the pathway result in vision loss or visual field deficits. Based on the type of presentation, the location of the lesion in the pathway can be ascertained.

Last updated: 1 Jun, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Visual Pathway

  • Light enters the eye and projects onto the retina 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 outermost layer is pigmented, whereas the inner nine layers are transparent. Eye: Anatomy, which contains photoreceptors:
    • Cones: 
      • Operate in bright-light conditions
      • Responsible for visual acuity 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. Ophthalmic Exam and color perception Perception The process by which the nature and meaning of sensory stimuli are recognized and interpreted. Psychiatric Assessment
    • Rods: 
  • Signals from the retinal photoreceptors  → go to bipolar Bipolar Nervous System: Histology cells  → then to the ganglion cells
  • Axons Axons Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body. Nervous System: Histology of the ganglion cells converge, forming the optic nerve 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. The 12 Cranial Nerves: Overview and Functions (CN II).
  • Optic nerve 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. The 12 Cranial Nerves: Overview and Functions to the optic tract:
    • Optic chiasm (OC): where hemidecussation of optic nerve 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. The 12 Cranial Nerves: Overview and Functions fibers occurs
    • Optic tract:
  • From the optic tract, most fibers synapse Synapse The junction between 2 neurons is called a synapse. The synapse allows a neuron to pass an electrical or chemical signal to another neuron or target effector cell. Synapses and Neurotransmission in the lateral geniculate nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles (LGN) of the thalamus Thalamus The thalamus is a large, ovoid structure in the dorsal part of the diencephalon that is located between the cerebral cortex and midbrain. It consists of several interconnected nuclei of grey matter separated by the laminae of white matter. The thalamus is the main conductor of information that passes between the cerebral cortex and the periphery, spinal cord, or brain stem. Thalamus: Anatomy, with some going to the superior colliculus Superior Colliculus The anterior pair of the quadrigeminal bodies which coordinate the general behavioral orienting responses to visual stimuli, such as whole-body turning, and reaching. Cranial Nerve Palsies
  • From each LGN, neurons 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. Nervous System: Histology travel in the optic radiations (geniculocalcarine fibers):
    • Inferior fibers: 
      • Inferior radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma is on the lateral side (lateral bundle) of the optic radiations.
      • Nerves extend anteriorly around the temporal horn of the lateral ventricle before proceeding posteriorly (Meyer’s loop).
      • Carry the information from the superior visual fields
    • Superior fibers:
      • The fibers that go superiorly, passing the parietal lobe 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. Cerebral Cortex: Anatomy, are on the medial side of the optic radiations.
      • Carry the information from the inferior visual fields
  • Primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy (striate or calcarine cortex, or V1 or area 17):
    • Optic radiations head posteriorly to the primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy.
    • The primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy area is mostly in the medial brain 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. Nervous System: Anatomy, Structure, and Classification surface of the occipital lobe 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. Cerebral Cortex: Anatomy.

Visual Fields

Anterior to the OC

  • Retina 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 outermost layer is pigmented, whereas the inner nine layers are transparent. Eye: Anatomy and optic nerve 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. The 12 Cranial Nerves: Overview and Functions: carry visual information on the ipsilateral or same eye where the nerve is located
  • OC:
    • Visual fields of each eye overlap considerably, to produce binocular vision Binocular Vision The blending of separate images seen by each eye into one composite image. Cranial Nerve Palsies and depth perception Perception The process by which the nature and meaning of sensory stimuli are recognized and interpreted. Psychiatric Assessment
    • The image from each half of the visual field is processed by the contralateral hemisphere. 
    • Left visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy (blue line) processes the information from the right half of the visual field. 
    • Right visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy (red line) processes the information from the left half of the visual field.
    • In order for each hemisphere to receive visual information from the contralateral visual field, the nasal fibers cross at the OC
Visual system

Diagram of the visual pathway and the visual fields: light enters the eye, sending signals to the retina 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 outermost layer is pigmented, whereas the inner nine layers are transparent. Eye: Anatomy and through the optic nerve 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. The 12 Cranial Nerves: Overview and Functions. The nasal fibers of each eye decussate at the optic chiasm, continuing to the optic tract with the temporal fibers: right nasal fibers join the left temporal fibers (blue lines) and the left nasal fibers join the right temporal fibers (red lines). Neurons 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. Nervous System: Histology synapse Synapse The junction between 2 neurons is called a synapse. The synapse allows a neuron to pass an electrical or chemical signal to another neuron or target effector cell. Synapses and Neurotransmission at the lateral geniculate nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles. Optic radiations connect the lateral geniculate nucleus Nucleus Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (cell nucleolus). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the endoplasmic reticulum. A cell may contain more than one nucleus. The Cell: Organelles to the primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy of the occipital lobe 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. Cerebral Cortex: Anatomy where visual information is processed.

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Posterior to the OC

  • Visual field information is processed in the contralateral hemisphere.
  • Optic tract and LGN:
    • Left visual field: represented by the right optic tract and LGN
    • Right visual field: represented by the left optic tract and LGN
  • Optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma and visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy:
    • From the LGN, neurons 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. Nervous System: Histology on both sides course to the visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy.
    • Inferior visual field: 
      • Carried by the superior part of the optic radiations 
      • Goes to the superior bank of the primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy
    • Superior visual field: 
      • Carried by the inferior part of the optic radiations (through Meyer’s loop)
      • Goes to the inferior bank of the primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy

Visual Field Defects

Unilateral visual field defect

  • Ocular pathology (e.g., lens Lens A transparent, biconvex structure of the eye, enclosed in a capsule and situated behind the iris and in front of the vitreous humor (vitreous body). It is slightly overlapped at its margin by the ciliary processes. Adaptation by the ciliary body is crucial for ocular accommodation. Eye: Anatomy, retina 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 outermost layer is pigmented, whereas the inner nine layers are transparent. Eye: Anatomy) or complete optic nerve 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. The 12 Cranial Nerves: Overview and Functions pathology:
    • Visual deficit: limited to 1 eye, same side of the lesion (monocular visual loss)
    • Contralateral eye sees normally.
  • Partial lesion of the optic nerve 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. The 12 Cranial Nerves: Overview and Functions:
    • If temporal fibers are affected: ipsilateral blindness 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. Retinopathy of Prematurity of the nasal visual field (nasal hemianopsia)
    • If nasal fibers are affected: ipsilateral blindness 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. Retinopathy of Prematurity of the temporal visual field (temporal hemianopsia)

Bilateral visual field defects

  • Site of lesion is the OC:
    • Where nasal fibers cross: Temporal visual fields are affected.
    • Visual defect: bitemporal heteronymous (different visual field affected in each eye) hemianopsia (loss of half of the visual field)
  • Site of lesion is the optic tract or lateral geniculate body (LGB)
    • Visual deficit is on the side contralateral to the lesion.
    • Contralateral homonymous (similar deficit in each eye) hemianopsia (loss of half of the visual field)
  • Site of lesion is the optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma or primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy:
    • Visual deficit is on the side contralateral to the lesion.
    • Optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma:
      • Inferior radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma or Meyer’s loop: contralateral superior quadrantanopsia
      • Superior radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma: contralateral inferior quadrantanopsia
      • All of optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma: contralateral homonymous hemianopsia
    • Primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy lesion: 
      • Inferior bank of the primary visual  cortex: contralateral superior quadrantanopsia
      • Superior bank of the primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy: contralateral inferior quadrantanopsia
      • Primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy: contralateral homonymous hemianopsia

Synopsis

Table: Overview of visual field defects
Site of lesion Visual field defect Description Possible cause
Macula Macula 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. Eye: Anatomy (central retina 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 outermost layer is pigmented, whereas the inner nine layers are transparent. Eye: Anatomy) Central scotoma 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. Cranial Nerve Palsies Ipsilateral central vision loss Central Vision Loss Macular Degeneration Optic neuritis 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). Cranial Nerve Palsies, retrobulbar neuritis Retrobulbar 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). Cranial Nerve Palsies
Optic nerve 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. The 12 Cranial Nerves: Overview and Functions Ipsilateral monocular blindness 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. Retinopathy of Prematurity/visual loss Blindness 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. Retinopathy of Prematurity in affected eye Optic neuritis 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). Cranial Nerve Palsies, retinal artery occlusion Retinal Artery Occlusion Retinal Vessel Occlusion, optic atrophy Atrophy Decrease in the size of a cell, tissue, organ, or multiple organs, associated with a variety of pathological conditions such as abnormal cellular changes, ischemia, malnutrition, or hormonal changes. Cellular Adaptation, trauma
OC (middle lesion) Bitemporal heteronymous hemianopsia Loss of temporal visual fields on both eyes Both Eyes Refractive Errors Pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types tumor Tumor Inflammation, craniopharyngioma Craniopharyngioma Craniopharyngiomas are rare squamous epithelial tumors with a solid and/or cystic structure that arise from the remnants of Rathke’s pouch along the pituitary stalk, in the suprasellar region. Craniopharyngiomas are histologically benign but tend to invade surrounding structures; thus, they should be treated as low-grade malignancies. Craniopharyngioma, meningioma Meningioma Meningiomas are slow-growing tumors that arise from the meninges of the brain and spinal cord. The vast majority are benign. These tumors commonly occur in individuals with a history of high doses of skull radiation, head trauma, and neurofibromatosis 2. Meningioma
Partial optic nerve 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. The 12 Cranial Nerves: Overview and Functions lesion Ipsilateral hemianopsia Loss of visual field on affected eye (temporal nerve injury Nerve Injury Surgical Complications: nasal hemianopsia; nasal nerve injury Nerve Injury Surgical Complications: temporal hemianopsia) Aneurysm Aneurysm An aneurysm is a bulging, weakened area of a blood vessel that causes an abnormal widening of its diameter > 1.5 times the size of the native vessel. Aneurysms occur more often in arteries than in veins and are at risk of dissection and rupture, which can be life-threatening. Thoracic Aortic Aneurysms, trauma
Optic tract Contralateral homonymous hemianopsia Loss of half of the visual fields opposite the lesion Brain 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. Nervous System: Anatomy, Structure, and Classification tumor Tumor Inflammation, abscess Abscess Accumulation of purulent material in tissues, organs, or circumscribed spaces, usually associated with signs of infection. Chronic Granulomatous Disease ( temporal lobe 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. Cerebral Cortex: Anatomy), middle cerebral artery Middle cerebral artery The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the cerebral cortex. These are the areas involved in motor, sensory, and speech activities. Cerebrovascular System: Anatomy infarction
Optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma (Meyer’s loop or inferior radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma/lateral bundle) Contralateral homonymous superior quadrantanopsia Loss of superior quadrant visual fields opposite the lesion (“pie in the sky”) Tumor Tumor Inflammation ( occipital Occipital Part of the back and base of the cranium that encloses the foramen magnum. Skull: Anatomy, temporal lobe 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. Cerebral Cortex: Anatomy)
Optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma (superior radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma/medial bundles) Contralateral homonymous inferior quadrantanopsia Loss of inferior quadrant visual fields opposite the lesion (“pie on the floor”) Tumor Tumor Inflammation ( occipital Occipital Part of the back and base of the cranium that encloses the foramen magnum. Skull: Anatomy, parietal lobe 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. Cerebral Cortex: Anatomy)
Optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma Contralateral homonymous hemianopsia Loss of half of the visual fields opposite the lesion Tumor Tumor Inflammation, middle cerebral artery Middle cerebral artery The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the cerebral cortex. These are the areas involved in motor, sensory, and speech activities. Cerebrovascular System: Anatomy infarction
Primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy Contralateral homonymous hemianopsia with macular sparing Loss of half of the visual fields opposite the lesion, but central vision Vision Ophthalmic Exam is maintained due to collateral circulation Circulation The movement of the blood as it is pumped through the cardiovascular system. ABCDE Assessment ( macula Macula 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. Eye: Anatomy receives blood supply from the middle cerebral artery Middle cerebral artery The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the cerebral cortex. These are the areas involved in motor, sensory, and speech activities. Cerebrovascular System: Anatomy) Posterior cerebral artery Posterior cerebral artery Artery formed by the bifurcation of the basilar artery. Branches of the posterior cerebral artery supply portions of the occipital lobe; parietal lobe; inferior temporal gyrus, brainstem, and choroid plexus. Cerebrovascular System: Anatomy thrombosis Thrombosis Formation and development of a thrombus or blood clot in the blood vessel. Epidemic Typhus, trauma, tumor Tumor Inflammation
Visual fields

Visual field defects:
1. injury to the right (R) macula Macula 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. Eye: Anatomy: right (R) central scotoma 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. Cranial Nerve Palsies
2. injury to the R optic nerve 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. The 12 Cranial Nerves: Overview and Functions: R visual loss
3. injury to the OC: bitemporal hemianopsia
4. injury to the R temporal optic nerve 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. The 12 Cranial Nerves: Overview and Functions: R nasal hemianopsia
5. injury to the R optic tract: left (L) homonymous hemianopsia
6. injury to the R Meyer’s loop: L homonymous superior quadrantanopsia
7. injury to the R superior optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma: L homonymous inferior quadrantanopsia
8. injury to the R optic radiation Radiation Emission or propagation of acoustic waves (sound), electromagnetic energy waves (such as light; radio waves; gamma rays; or x-rays), or a stream of subatomic particles (such as electrons; neutrons; protons; or alpha particles). Osteosarcoma: L homonymous hemianopsia
9. injury to the R primary visual cortex Visual cortex Area of the occipital lobe concerned with the processing of visual information relayed via visual pathways. Cerebral Cortex: Anatomy: L homonymous hemianopsia with macular sparing due to collateral blood supply

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Clinical Relevance

  • Ischemic optic neuropathy Neuropathy Leprosy (ION): a condition secondary to reduced blood flow Flow Blood flows through the heart, arteries, capillaries, and veins in a closed, continuous circuit. Flow is the movement of volume per unit of time. Flow is affected by the pressure gradient and the resistance fluid encounters between 2 points. Vascular resistance is the opposition to flow, which is caused primarily by blood friction against vessel walls. Vascular Resistance, Flow, and Mean Arterial Pressure leading to optic nerve 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. The 12 Cranial Nerves: Overview and Functions damage. Risk factors include age > 50, diabetes Diabetes Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia and dysfunction of the regulation of glucose metabolism by insulin. Type 1 DM is diagnosed mostly in children and young adults as the result of autoimmune destruction of β cells in the pancreas and the resulting lack of insulin. Type 2 DM has a significant association with obesity and is characterized by insulin resistance. Diabetes Mellitus, and hypertension Hypertension Hypertension, or high blood pressure, is a common disease that manifests as elevated systemic arterial pressures. Hypertension is most often asymptomatic and is found incidentally as part of a routine physical examination or during triage for an unrelated medical encounter. Hypertension. Ischemic optic neuropathy Neuropathy Leprosy can be arteritic (due to giant cell arteritis Giant Cell Arteritis Giant cell arteritis (GCA), also known as temporal arteritis, is a type of large-vessel vasculitis that predominantly affects the aorta and its major branches, with a predilection for the branches of the carotid (including the temporal artery). Giant cell arteritis is defined by inflammatory leukocytes in the vessel walls leading to reactive damage, ischemia, and necrosis. Giant Cell Arteritis) or non-arteritic (other causes), which is more frequent. Non-arteritic ION presents as an acute, painless monocular visual loss associated with an altitudinal visual field defect. 
  • Middle cerebral artery Middle cerebral artery The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the cerebral cortex. These are the areas involved in motor, sensory, and speech activities. Cerebrovascular System: Anatomy (MCA) infarction: the middle cerebral artery Middle cerebral artery The largest of the cerebral arteries. It trifurcates into temporal, frontal, and parietal branches supplying blood to most of the parenchyma of these lobes in the cerebral cortex. These are the areas involved in motor, sensory, and speech activities. Cerebrovascular System: Anatomy supplies the frontal Frontal The bone that forms the frontal aspect of the skull. Its flat part forms the forehead, articulating inferiorly with the nasal bone and the cheek bone on each side of the face. Skull: Anatomy, parietal Parietal One of a pair of irregularly shaped quadrilateral bones situated between the frontal bone and occipital bone, which together form the sides of the cranium. Skull: Anatomy, and temporal lobes. Ischemic stroke Ischemic Stroke An ischemic stroke (also known as cerebrovascular accident) is an acute neurologic injury that occurs as a result of brain ischemia; this condition may be due to cerebral blood vessel occlusion by thrombosis or embolism, or rarely due to systemic hypoperfusion. Ischemic Stroke affecting the MCA area can manifest as contralateral homonymous hemianopsia. Presentation is usually with other findings including contralateral hemiparesis Hemiparesis The term hemiparesis refers to mild to moderate weakness involving one side of the body. Epidural Hemorrhage and sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology loss with aphasia Aphasia A cognitive disorder marked by an impaired ability to comprehend or express language in its written or spoken form. This condition is caused by diseases which affect the language areas of the dominant hemisphere. Clinical features are used to classify the various subtypes of this condition. General categories include receptive, expressive, and mixed forms of aphasia. Ischemic Stroke.
  • Pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types adenoma: benign Benign Fibroadenoma tumor Tumor Inflammation of the pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types gland, which sits inferior to the OC. Suprasellar extension Extension Examination of the Upper Limbs of the adenoma compresses the OC and produces bitemporal hemianopsia. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship also have headaches and symptoms of pituitary Pituitary A small, unpaired gland situated in the sella turcica. It is connected to the hypothalamus by a short stalk which is called the infundibulum. Hormones: Overview and Types dysfunction: infertility Infertility Infertility is the inability to conceive in the context of regular intercourse. The most common causes of infertility in women are related to ovulatory dysfunction or tubal obstruction, whereas, in men, abnormal sperm is a common cause. Infertility and galactorrhea Galactorrhea Excessive or inappropriate lactation in females or males, and not necessarily related to pregnancy. Galactorrhea can occur either unilaterally or bilaterally, and be profuse or sparse. Its most common cause is hyperprolactinemia. Hyperprolactinemia, among others.
  • Foster-Kennedy syndrome: presents with bilateral visual problems and is due to an enlarging intracranial mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast compressing on the ipsilateral optic nerve 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. The 12 Cranial Nerves: Overview and Functions, resulting in ipsilateral optic neuropathy Neuropathy Leprosy. Blurry vision Vision Ophthalmic Exam is bilateral because the increased intracranial pressure Increased Intracranial Pressure Normal intracranial pressure (ICP) is defined as < 15 mm Hg, whereas pathologically increased ICP is any pressure ≥ 20 mm Hg. Increased ICP may result from several etiologies, including trauma, intracranial hemorrhage, mass lesions, cerebral edema, increased CSF production, and decreased CSF absorption. Increased Intracranial Pressure (ICP) from the mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast causes papilledema 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. Idiopathic Intracranial Hypertension on the contralateral eye.

References

  1. Berkowitz, A.L. (Ed.). (2016). Clinical Neurology and Neuroanatomy: A Localization-Based Approach. McGraw-Hill.
  2. Kibble, J.D. (Ed.). (2020). Neurophysiology in The Big Picture Physiology: Medical Course & Step 1 Review, 2e. McGraw-Hill.
  3. Martin, J.H. (Ed.). (2021). The visual system in Neuroanatomy: Text and Atlas, 5e. McGraw-Hill.
  4. Purves, D., Augustine, G., & Fitzpatrick, D. (Eds.). (2001). Visual field defects in Neuroscience (2nd ed.). Retrieved from https://www.ncbi.nlm.nih.gov/books/NBK10912/
  5. Shakkottai, V.G., & Lomen-Hoerth, C. (2019). Nervous system disorders. In Hammer, G.D., & McPhee, S.J. (Eds.), Pathophysiology of Disease: An Introduction to Clinical Medicine, 8e. McGraw-Hill. 
  6. Waxman, S.G. (Ed.). (2020). The visual system. Clinical Neuroanatomy, 29e. McGraw-Hill.

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