Visual Pathway Flashcards
location where retinal nerve fibers make a 90 degree turn
optic disk
blind spot
- complete absence of all retinal layers except NERVE FIBER LAYER and INTERNAL LIMITING MEMBRANE
- absolute scotoma resulting from lack of photoreceptors in the optic disc
Intraocular segment
- inside the globe
- contains two segments (1) prelaminar (2)laminar
- roughly 1mm
Intermediary tissue of Kuhnt
Separation from RETINAL LAYERS by glial tissue
Border tissue of Jacoby
Separation from CHOROID by glial tissue
Marginal (border) tissue of Elschnig
Ring of collagenous tissue of scleral origin, outer to glial sheath
prevents leakage from choriocapillaris
tight junctions in the border tissue of jacoby
papillomacular bundle
the nerve fiber layer that goes from the macula to the optic disc - temporal side of disc (1/3)
superior and inferior retinal fiber cannot pass what border?
horizontal raphe
Thickest retinal disc portion
inferior
Thinnest portion of optic disc
temporal
ISNT rule
- inferior (thickest) > superior >nasal >temporal (thinnest)
- counterclock wise thickness from inferior to superior temporal
- fovea is located slightly inferior to center more axons enter the temporal side inferiorly than superiorly
- arrangement changes AFTER optic disc
intraorbital portion of optic nerve
- orbit portion (globe to apex)
- longest portion(roughly 30 mm)
- surrounded by rectus sheath
which rectus muscles are interconnected to the sheath of the optic nerve?
superior and medial rectus
Dura Mater of optic nerve
(1) outermost (2) dense connective tissue (3) elastic fibers (4) fuses with arachnoid and pia mater to become continuous with sclera and periorbita
Arachnoid of optic nerve
(1) middle meningeal (2) thin collagenous membrane (3) fuses with dura mater and pia mater to become continuous with sclera and periorbita
Pia Mater of optic nerve
(1) innermost (2) vascular connective tissue (3) fuses with arachnoid and dura to become continuous with sclera and periorbita (4) ONLY meningeal sheath continuous along INTRACRANIAL portion
Myelination
(1) oligodendrocytes (CNS) (2) absent in retina - lamina cribrosa barrier
Subarachnoid space of optic nerve
(1) space between arachnoid and pia mater (2) contains cerebrospinal fluid (3) continuous with intracranial subarachnoid space
Astrocytes
provide structure, store glycogen, and regulate extracellular concentration of ions
Intracanlicular portion of optic nerve
portion through the optic canal, appx 10 mm
Intracranial portion of the optic nerve
the portion in the brain? appx 15 mm
optic canal
area between lesser wing of sphenoid and the sphenoid body
blood supply to the nerve fiber layer
radial peripapillary capillary plexus (central retinal artery) - surface of NERVE FIBER LAYER
blood supply to the intraorbital portion of the optic nerve
pial plexus (opthalmic artery)
blood supply to intracanicular portion of the the optic nerve
pial plexus (opthalmic artery)
blood supply to the intracranial portion of the optic nerve
(1)Pial plexus (opthalmic artery), (2)anterior cerebral artery, (3)anterior communicating and (4)internal carotid artery
blood brain barrier
capillaries within the optic nerve composed of nonfenestrated endothelium joined by zonula occludens
blood supply to the Prelaminar portion of the optic nerve
peripapillary choroid (SPCAs)
blood supply to the LAMINAR portion of the optic nerve
circle of zinn and SPCAs
structure that lies within the “circle of willis”
optic chiasm
blood supply of anterior cranial regions
internal carotid
blood supply of posterior cranial regions
basilar artery
most anterior portion of “circle of willis”
anterior cerebral artery
anterior knees of wilbrand
loop back into opposite optic nerve before turning around and exiting as opposite optic tract
posterior knees of willibrand
loop forward into same side optic nerve before crossing to join opposite optic tract
superior network
anterior cerebral and anterior communication arteries
inferior network
internal carotid, posterior cerebral and posterior communicating arteries
optic tract
runs from posterolateral corner of optic chiasm to LGN - composed of axons of retinal ganglion cells
pretectal nucleus
alternate pathway from optic chiasm - PUPIL LIGHT REFLEX
optic tract to HYPOTHALAMUS
CIRCADIAN RHYTHYM
Optic tract to SUPERIOR COLLICULUS
visual orientation and control of saccadic eye movements
orientation of superior fibers in optic tract
medial
orientation of inferior retinal fibers in optic tract
lateral
orientation of macular fibers in optic tract
macular
optic tract blood supply
anterior choroidal artery and middle cerebral artery
LGN
(lateral geniculate nucleus) located in the thalamus - center of complex processing
where do retinal axons terminate/synapse
LGN
optic radiations
LGN -> visual cortex
magnocellular layers
first 2 inferior layers (layers 1 and 2) - spatial recognition and motion detection
parvocellular layers
4 most superior layers (layers 3-6) - detail and colored vision
portion of LGN that receive input from contralateral retina
layers 1,4,6
portion of LGN that receive input from ipsilateral retina
layers 2,3,5
retinotopic map
point to point localization of the retina
LGN blood supply
anterior choroidal artery, lateral choroidal artery, and posterior choroidal artery
meyer loops
loop around tip of lateral ventricle in temporal lobe
inferior radiations
(inferior retina) lateral aspect of LGN > temporal lobe > meyer loops >occipital lobe
superior radiations
(superior retina) medial aspect of LGN > parietal lobe > occipital lobe
anterior radiation blood supply
anterior choroidal artery and middle cerebral artery
middle radiation blood supply
deep optic branch of the middle cerebral artery
posterior radiation blood supply
posterior cerebral artery, calcarine artery, middle cerebral artery
macular sparing
central vision remains despite a homonymous defect (thanks to middle cerebral artery)
prechiasmal VF defect
damage anterior to optic chiasm - field defects usually monocular
postchiasmal VF defect
damage to posterior to optic chiasm - field defects on contralateral side
chiasmal VF defect
within optic chiasm - bitemporal or binasal field defect
congruent VF defect
two defects are similar in shape between both eyes
incongruent VF defect
defect shapes are dissimilar between both eyes
Striate cortex blood supply
calcarine branch (posterior cerebral artery)
striate cortex
combines and analyzes visual information and transmits to higher visual association areas - PRIMARY VISUAL CORTEX
extrastriate cortex
higher visual associated areas
Brodmann areas 18 and 19
lateral aspects of occipital lobe (extrastraite cortex)
Brodmann areas 17 or VI
medial surface of occipital lobe (striate cortex)
white striae of gennari
myelinated fiber layer of LGN unique to visual cortex
calcarine fissure
divides striate cortex in 2 halves - CONTAINS most of primary visual cortex
cuneus gyrus
upper half of striate cortex
lingual gyrus
lower half of striate cortex
horizontal layers of striate cortex
layers 1,2,3
Layer IV of striate cortex
contains the stria of gennari - contains sublayer, each which recieve either magnocellular or parvocellular layers of LGN
layer VI of striate cortex
sends projections back to LGN
frontal eye fields
found in frontal lobe, receive fibers from striate cortex that contribute to CONJUGATE EYE MOVEMENTS as well as pupillary responses to near objects
termination of superior optic radiations
cuneus gyrus (above calcarine fissure)
termination of inferior optic radiations
lingual gyrus (below calcarine fissure)
