Eye And Orbit Flashcards
Bones of the orbit
- Frontal
- Maxillary
- Zygomatic
- Lacrimal
- Sphenoid
- Palatine
- Ethmoid
Orbital openings
- Optic canal
- Superior orbital fissure
- Inferior orbital fissure
Trigeminal n. In the orbit
- Ophthalmic branches (V1): sensory to orbit
- Maxillary (V2): carry parasympathetic from CN VII -> lacrimal gland
A. Sympathetic: pre-synaptic (T1) -> superior cervical ganglion - synapse -> internal carotid plexus (V1) -> eye
Fontal n.
Branch off ophthalmic (V1)
1. Supraorbital and supratroclear -> sensory to skin of forehead
Lacrimal n.
Branch of ophthalmic (V1)
- Parasympathetic travel w/ lacrimal n. From communicating zygomatic branch (V2)
- Sensory to lacrimal and upper eyelid/tarsal plate
Nasociliary n.
- Long and cohort ciliary branches carry sympathetic and somatic afferent -> eye
- Short ciliary parasympathetic from ciliary ganglion and some somatic afferent -> eye
- Anterior and posterior ethmoid branches: parasympathetic (from CN VII) and sensory -> mucosa nasal cavity, sphenoid sinus, ethmoid air cells
- Infratrochlear branch: sensory -> external nose
Extrinsic eye muscles
- Superior rectus (CN III)
- Inferior rectus (CN III)
- Medial rectus (CN III)
- Lateral rectus (CN VI)
- Superior oblique (CN IV)
- Inferior oblique (CN III)
Superior rectus m.
- Prox: common tendinous ring
- Distal: top of tee
- Innervation: CN III
- Fxn: primary elevation, adduction, medial rotation
Inferior rectus m.
- Prox: common tendinous ring
- Distal: bottom of eye
- Innervation: CN III
- Fxn: primary depression, adduction, lateral rotation
Medial rectus m.
- Prox: common tendinous ring
- Distal: medial aspect of eye
- Innervation: CN III
- Fxn: adduction
Lateral rectus m.
- Prox: common tendinous ring
- Distal: lateral aspect of eye
- Innervation: CN VI
- Fxn: abduction
Superior oblique m.
- Prox: common tendinous ring
- Distal: wraps around trochlea -> lateral posterior aspect of eye
- Innervation: CN IV
- Fxn: depression, abduction, medial rotation (down and out)
Inferior oblique m.
- Prox: anterior/medial/inferior aspect of orbit
- Distal: lateral posterior aspect of eye
- Innervation: CN III
- Fxn: elevation, abduction, lateral rotation (up and out)
H test
Active eye muscle test
- Pt abducts then elevates and depresses eyes
- Pt adducts then elevates and depresses
- Add/abd tests medial/lateral rectus
- Add + elevation = inferior oblique
- Add + depression = superior oblique
- Superior/inferior rectus m. Useless in adduction
Eyelids
Skin covering superior and inferior tarsal plates w/ palpabrae conjunctiva underneath
1. Fxn:
A. Close eye: orbicularis oculi (CN VII)
B. Open eye: levator palpabrae superioris (CN III) and superior tarsal (symp from T1)
2. Tarsal (Meibomian) glands
Tarsal (Meibomian) glands
Line internal tarsal plates -> meibum
1. Meibum: prevents tear evaporation and protects eyes
Sclera
Opaque, white part of of eye where extrinsic m. Attach
Cornea
Transparent layer covering lens
Choroid
Vascular layer between sclera and retina
Iris
Contractile diaphragm of surface of the lens
1. Layers
A. Stroma: fibrous and vascular
B. Pigmented
2. Sphincter pupillae: constricts pupil
A. Parasympathetic CN III via short ciliary n.
3. Dilator pupillae: opens pupil
A. Sympathetic from long and short ciliary n.
Ciliary m. And body
- Vascular -> aqueous humor
- Muscular: series of smooth circular m. Attached to lens thru zonules (suspensory lig)
- Accommodation: dec tension of zonules when muscles contract -> lens rounder (thicker) - focus on closer objects
- Innervation: parasympathetic from CN III via short ciliary n.
Retina
Sensory nervous layer of the eye
1. Optic part: pigmented outer layer and light receptor layer
2. Ciliary part: covers ciliary body, pigmented outer layer
3. Iridial part: covers iris, both layers pigmented
4. Optic disk: “blind spot” where optic n. Enters
5. Macular: “yellow spot” area of cones (color)
A. Fovae centralis: area of most acute vision in center
Anterior and posterior aqueous chambers of the eye
Supply lens and cornea w/ nutrients
1. Ciliary body -> aqueous humor in posterior chamber -> anterior chamber -> recycled into venous system via canal of achlemm
Vitreous body of the eye
Posterior to lens and anterior chamber
- Provides constant pressure and space for proper focal distance
- Filled w/ vitreous humor
Ophthalmic a.
Blood supply to the eye
Branches:
1. central retinal a.: pierces optic n. And supplies retinal n. (Expect rods and cones)
2. Long and short posterior ciliary a. -> choroid capillary plexus -> rods and cones
3. Lacrimal a. -> lacrimal glands
4. Branches exited orbit -> face/nasal cavity
A. Supraorbital
B. Supratrochlear
C. Dorsal nasal
D. Anterior/posterior ethmoid
Lacrimal apparatus
- Inflow: lacrimal gland -> ducts -> eye
- Outflow: across eye medially -> lacrimal canaliculi -> lacrimal sac and nasolacrimal duct -> nasopharynx under inferior nasal concha
- Parasympathetic stimulation of lacrimal gland from pterygopalatine (CN VII) -> zygomatic (CN V2) -> lacrimal branch of frontal (V2) via zygomaticcommunicating n.
- Sympathetic dec secretion
