Eye Flashcards
Gimme everything you got for this
- Light pathway from eyeball to dorsal and ventral pathways
- all pathways
- Occipital lobe & Visual Field
Light Cornea Pupil - shape of HOLE Lens - refraction - Fovea (Retina)
Photoreceptors - Bipolar Cells - Ganglion Cells
Optic Disc // Optic Nerve
Optic Chiasm - nasal fibers decussate
Optic tract - Reflex arc splits out to Pretectal Nc (Pupil) or Superior Colliculi (Accommodation-Convergence)
Optic tract synapse at Lateral Geniculate Nucleus @ Thalamus
Then Optic Radiation
- inferior fibers w Superior visual field goes to Temporal Lobe as Meyer’s Loop
Then end up at Occipital Lobe Primary Visual Cortex
- Dorsal Visual Pathway to Parietal lobe for SPATIAL, MOTION
- Ventral Visual Pathway to Temporal lobe for FORM, COLOR
- 10 degree WRT Fovea is 55% of occipital lobe; tip of lobe is centre of vision
- we are foveate animals
- supplied by both PCA and MCA hence macular sparing
Describe what
- Left Retina corresponds to
- Right Visual Cortex
- Nasal Field
Left Retina - Right Visual Field
Right Visual Cortex - Left Visual Field
Nasal Field (WRT to eyes) goes to temporal retina of both eyes
Describe the accommodation reflex w CN involvements
- give all functions
- plus how Aqueous Humor is involved
Near item
- CN II optic nerve
- Optic tract
- Goes to Superior Colliculi @ Brainstem
- Goes to Edinger-Westphal Nc of CNIII @ Brainstem
Parasympathetic function of CNIII - synapse at Ciliary Ganglion
- Ciliary Muscle contract, Zonular Fibers relax
- Lens become more spherical, diameter decrease, thickens
- Sphincter Pupillae contracts - Pupil CONSTRICTS - for depth of focus
- CN III - oculomotor nerve - Medial Rectus adducts eyeballs
- Note ciliary contraction opens trabecular meshwork - improving drainage of AH, decreasing IOP
- Hence result of Pilocarpine, a MR agonist for parasympathetic
Whats Presbyopia
Lens rigidity, losing Ciliary Muscle efficiency
- causing long sightedness
- Hyperopia (other is Myopia)
Compare and Contrast Rods and Cones
BOTH 0 AT BLIND SPOT - Optic Disc
High Sensitivity, Low resolution hence Low acuity
15:1 ratio of PR to Bipolar cells - weak amplification
Achromatic Vision
0% at Fovea, increase to max at 15 degree then decreases - hence peripheral vision
Slow response, recovery
MORE IN NUMBERS but fewer types of pigment 1 VS 3
Low Sensitivty, High resolution, high acuity
1:1 ratio - strong amplification; high photons
Color vision
Peak at fovea, then drop; 15 degree onwards constant low
Fast response, recovery
Fewer in number, more types;
Central vision
What is being carried by left Meyer’s Loop
Inferior right retina quadrant
Superior right visual field
Gimme defects of
Right Optic Nerve Optic Chiasm Right Optic Tract Right Meyer's Loop Right Occipital Cortex - why
Right monocular blindness
Bitemporal Hemianopia - Pituitary adenoma
Left Homonymous Hemianopia
Left Superior Quadrantanopia
Left Homonymous Hemianopia w Macular Sparing
- TIP of occipital lobe w center vision by MCA
- PCA supplies rest; if stroke both out then no sparing
Where are the CNs given off
Midbrain 3, 4
Pons 5
Pontomedullary Junction 678
Medulla 9 10 11 12
CN3 lesion
- nerves, pathways, ganglions
Eye Down and Out
- unopposed Lateral Rectus, Superior Oblique
- Hence diplopia except lateral gaze to involved side cos other side MR ok; LR6 on your side ok
Drooping Eyelid - Ptosis
- Levator Palpebrae Superioris
NOTE smooth eyelid muscle superior tarsal muscle by some sympathetic nerve;
CN4 Lesion
CN6 Lesion
CN4 Lesion
- Medial Rectus ok - Adduction at rest
CN6 Lesion
- elevated eye
- recall Superior Oblique depresses and extorts
- both obliques abducts;
Gimme the reflex pathways of
- accommodation-convergence
- Pupil reflex
AC: Optic tract to Superior Colliculus - then to EWN, CN3, CN4, CN6
Pupil Reflex: Optic tract to Pretectal Nu - then to EWN
- ciliary contract only
