The Visual System Flashcards
Pathway for light
Light-> to posterior chamber-> through all layers of the retina by the bipolar cells included-> back to layer 2 of the retina by ganglionic cells-> brain LGN of thalamus-> primary visual cortex and the calcarine sulcus
Three layers of the eye
Fibrous Layer: external layer, SCLERA and CORNEA
Vascular Layer: CHOROID, CILIARY BODY, IRIS
Retina: inner sensory layer, OPTIC NERVE
Fibrous Layer: Sclera and cornea
- Sclera: fibrous external layer- protection and extraocular muscles insertion anteriorly
type 1 collagen, Dense Regular CT, some vasculature - Cornea: transparent and avascular (can be injured and fixed)
a. Corneal epithelium- nonkaratinized strat. squamous
b. Anterior limiting membrane (Bowman Membrane)- BM of the corneal epithelium
c. Thick Stroma - keratocytes
d. Posterior limiting membrane (Descemet’s Membrane)- BM for the endothelium layer
e. Inner endothelium
The Limbus
Transition from the cornea to the sclera.
This is the end of the bowman membrane
This is the start of the conjunctiva (anterior sclera and lines eyelids)
Has stem cells that move to the corneal epithelium
Vascular Layer (uvea): choroid
- Choroid: loose CT, high vascularized, many MELANOCYTES, where light that is not reflected off the retina goes
dark layer- prevent light from entering eye except through pupil
bruch membrane- Basal lamina for retina pigment layer (anterior boundary for the choroid)
Vascular Layer (uvea): ciliary body
- Ciliary Body: shape of LENS, ciliary muscels, processes, zona
Vascular Layer (uvea): Iris
- Iris: makes the pupil in the middle, outer boundary of the lens
Retina: makes the optic cup
- Outer Pigment Epithelium layer- simple cuboidal (surrounds the neuronal layer)
- Inner Neural Layer- think strat. with many neurons and photoreceptors (10 LAYERS)
optic disk
blind spot
fovea
highest acuity vision, highest amount of cones
Peripheral retina including the ora serrata
high rods
Pigmented Epithelium layer
surrounds the neural layer
- absorbs scattered light: helping choroid
- Isomerize all-trans -> 11- cis and takes it back to the photoreceptors
- Phagocytosis of waste form photoreceptors
- Remove free radicals and secretes ATP
- immunomodulatory factors
Neuronal Retina 10 layers
LIGHT–>through all layer to the bottom layer
- Pigmented Layer
- Rods and Cones outer segments
- Outer Limiting Layer: hold photoreceptors to müller cells
- Outer Nuclear Layer- rods and cones cell bodies
- Outer Plexiform Layer: fiber/axons of R/C–> Bipolar Cells
- Inner Nuclear Layer: Bipolar Cells
- Inner Plexiform Layer: fiber/axons of Bipolar cells –> Ganglionic Cells
- Ganglionic Layer: Ganglionic cell bodies (thicker in the center of the retina)
- Nerve Fibre Layer: Ganglionic axons that go to OPTIC DISC and converge to form CN1
- Inner Limiting Membrane: BM covered by Müller cell processes
Rods Inner Segment
Inner Segment= glycogen, mitochondria, polyribosomes, to make proteins for cells
Rods Outer Segments
Outer Segment= primary cilium, photosensitive, has flattened membranous discs
Rods Outer Segments - DISCS
Has rhodopsin
continuously shed and replaced
old disc= pushed superficially to be shed and digested by PE
Cones
color vision if there is adequate bright light
has 3 types of IODOPSIN
Red, Green, Blue
discs are shed not as often
Specialized area of the Retina - FOVEA CENTRALIS
highest cones, 20/20 acuity, in the center of the retina
as you move peripherally the acuity becomes more 20/600
HAS NO BVS, Cell bodies/Axons of the Ganglionic and Inner Nuclear Layer (bipolar cells)
Specialized area of the Retina - MACULA LUTEA
surrounds fovea for protection of cones
uv filter and antioxidant
Specialized area of the Retina - Optic Disc
Head of the optic Nerve,
only ganglionic axons, BLIND SPOT
Specialized area of the Retina - Optic Nerve
Axons of the ganglionic cells, get myelinated when they pass through the sclera
go to brain
Visual Field
what I see when both eyes are looking in a direction
- Binocular Zone= broad central region (both eyes)
- Monocular Zone= seen by only one eye
Retinal Field
object projected in the retina in the reverse way both laterally and vertically
Lesions in the visual system
described using the visual filed deficiency
LEFT HALF OF VISUAL FIELD is from what
left nasal hemifield and right temporal hemifield
RIGTH HALF OF VISUAL FIELD is from what
right nasal, left temporal
What lets us have depth perception
the decussation of at the optic chiasm
OPTIC TRACT: after the optic nerve has crossed- temporal halves (same side)+ nasal halves (opposite visual field side) which travel to the LGN
Opitc Tract
goes around cerebral peduncle to LGN in a retinotopic pattern and go to the primary visual cortex as optic radiations
Temporal Retina
go to SAME LGN
Nasal Retina
go to OPPOSITE LGN
RIGHT Visual FIELD goes to which side of LGN
LEFT LGN
Right nasal + Left Temporal —>Left
LEFT Visual FIELD goes to which side of the LGN
RIGTH LGN
Left nasal + Right Temporal—->Right
optic radiations
from LGN to primary visual cortex, where the retinotopic organization is maintained
where in the primary visual cortex
the upper bank (cuneus gyrus) and lower bank (Lingual gyrus) of the Calcarine Sulcus
Lower Quadrant of visual field side (upper part of object)
OPPOSITE and Superior bank (CUNEUS GYRI)
Lower Quadrant of visual field side (upper part of object)
OPPOSITE and V1 Superior bank (CUNEUS GYRI)
Upper Quadrant of visual field side (bottom part of object)
loops around the Meyer loop to the OPPOSITE and V1 Inferior bank (LINGUAL GYRI)
something you see on the upper right quadrant of an object
go to the lower left visual cortex
something you see on the upper right quadrant of an object
go to the lower left visual cortex
loops around the Meyers loop if from the upper quadrant
Superior Colliculus
DIRECTS EYE MOVEMENT visual reflex causes head to turn
Pretectal Area
unconscious responses, PUPILLARY LIGHT REFLEX
Hemianopia
blindness in 1/2 of the visual field
Quadrantanopia
blindness in a quadrant of the VF
Homonymous Visual Fields
VF loss is the same on both eyes
Heteronymous visual fields
VF losses are different in both eyes
Macular Sparing
VS loss that still keeps the vision in the center of the visual field
uncommon
optic tract and optic radiation lesions
CONGRUOUS or INCONGRUOUS
- Congruous= VF loss in one eye is superimposed on the other eye (symmeterical)
more posterior closer to the visual cortex lesions - Incongruous= VF loss in one eye can not be superimposed on the other eye
more anterior closer to the optic tract and optic radiation lesion
Damage to the anterior chiasm effecting only the SAME eye
Congruous
Damage at chiasm causes heteronymous deficits
Incongruous
damage behind the chiasm causes homonymous deficits
Congruous
PCA Damage can cause
Left occipital lobe or posterior corpus callosum damage
=language is disconnected from vision
patient is unable to name or describe any object
However, recognizes and can use the object
= can also effect writing and reading
