Chapter 19 Opticals Flashcards
Fibrous Tunic
- sclera (white)
- cornea (transparent)
Vascular Tunic
- choroid
- ciliary body
- iris
Neural Tunic
retina
What keeps muscles in the eye in place?
lots of fat
Three tunics form the ‘globe’ of the eye:
fibrous, vascular, neural
Sclera
- attachment site for extrinsic eye muscles
- elastic/mechanical support
What does the cornea bulge do?
refracts light before it hits lens
Choroid
-vascular = helps nourish retina
-black pigmentation absorbs “stray” light
(waffe-like in lab)
Ciliary body
- muscle & ligaments
- smooth muscle (radial and sphincter-like fibers)
- suspensory “ligament” of the lens
Iris
- color of eye
- smooth muscles (radial and sphincter-like) fibers
- muscle contraction = diameter of pupil
What fills the anterior cavity?
aqueous humor
aqueous humor
- produced by the ciliary process
- returned to blood supply via the Canal of Schlemm
- helps control intra-ocular pressure
What fills the posterior cavity?
vitreous humor (gel-like)
vitreous humor
helps maintain shape of eyeball
Suspensory ligament
- barrier btw ant/post cavities
- lens is suspended btw layers
Glaucoma
- circulation of aqueous humor is blocked (disease of anterior cavity)
- increased pressure > damage to optic nerve
- edema of the cornea > cloudy/grey-green eye
- associated w/ high blood pressure
Posterior pigmented layer of the retina
-dark pigmentation absorbs stray light
Anterior ‘neural layer’
- contains 9 layers
- ganglia = integration & preliminary processing
Rods
- light & dark
- cheap to operate
Cones
- color
- absence =color blindness
- expensive to operate
Macula lutea & the Fovea centralis
- center of visual axis
- contains high conc. of cones
- sharpest focus
Blind spot (optic disk)
- point where optic nerve exits the globe
- point where blood vessels enter/exit the globe
- located very close to and medial of the fovea
Globe of the eye and the retina
- formed as lateral diverticula of the diencephalon
- appears to be installed backwards
Mechanical limitations
- rod & cones point the wrong way
- receptors buried behind 9 layers
- blind-spot where axons & blood vessels leave globe
Result of mechanical limitations
70% of the image is lost (only 30% efficient)
Pineal gland
- tied to light reception: diurnal behavior patterns
- tied to sleeping & melatonin
- seat of the soul
Why do eyes turn red w/ flash?
bc of so many blood vessels in the back of the eye
Gray matter
rods/cones - deep layer
White matter
vasc/ganglia - superficial layer
Iris (CN III):
- antagonist muscles
- sympathetic stimulation > dilation of pupil
- parasympathetic stimulation > contraction of pupil
Ciliary muscle (CN III)
- contraction affects how lens is stretched
- shape of lens affects where eye focuses
Do ciliary muscles pull on suspensory ligaments?
NOO
Lens
- suspended from sclera by suspensory ligament
- no BV’s present
Photic sneeze reflex
-parasym. tries to close eye to limit light connected w/ nose so believes something in nose
Accommodation
- ability to focus
- requires change in lens shape
Close objects
- parasympathetic
- ciliary muscles contract, ligaments sag, & lens bulges
Far objects
- sympathetic
- ciliary muscles relax, ligaments tighten, & lens thins
Can the lens move?
no, only change shape
Presbyopia
- lens proteins become “stiffer” with old age
- can’t focus on near objects = far-sighted
Cataracts
- lens becomes cloudy
- focusing becomes “patchy” across retina
Astigmatism
- refractive errors of the cornea
- glases/lenses help w/ correction
Levator palpebrae superioris
lifts upper eyelid (CN III)
Orbicularis oculi
closes both eyelids (CN VII)
Palpebrae
upper & lower eyelids
Caruncle
lacrimal
Canthi
medial near caruncle & lateral canthus
-corner
Conjunctiva
- skin over anterior surface of eye
- pink-eye
Lacrimal gland
- superolateral corner of orbit
- wash, moisten, minimize friction
Lacrimal apparatus
-tears are squeezed into medial canthus with each blink
How tears drain?
lacrimal puncta > lacrimal canaliculi > lacrimal sac > nasolacrimal duct > nasal cavity
Trochlea
sling of CT for superior oblique muscle
