Vision Flashcards
Muscles that move eyebrows
corrugator supercilii: move them medically
orbicularirs oculi - brings them down
What separates the eyelids
palpebral fissure : white space of eyes
medial + lateral commissaries: connect upper and lower eyelids
T or FL The orbicularis oculi opens/lifts the top eyelid
F
levator palpebrae superioris: open and lift top eyelid
orbicularis oculi: closes top lid only
Where are tarsal glands and what do they do
embedded in tarsal plates in top and bottom eyelids
- produce oily shit that lubs the edges and prevents leakage out of eyes
Conjunctiva: types and functions
- lines eyelids (palpebral) and whites of eyes (ocular, expect cornea)
- lubricates and protects eye
- continuous with each other
Function of the lacrimal apparatus + its parts
- secretes tears (contain mucous, AB, and lysozyme)
leave gland via excretory glands (secrete at lateral edge) , collects at punctum into lacrimal canal —- to the sac and drain via nasolacrimal duct
T or F: the lacrimal caruncle secretes tears
F - oily secretion at night
acro. to remember extrinsic eye muscles and what they are innervated by
LR6SO4R3
Inf. oblique : moves eye up laterally + counterclockwise
Sup. oblique: moves eye laterally and clockwise
What layer of the eye is continuous with the iris
the choroid (where BV are)
What is the fibrous tunic
outermost layer made up of sclera (white, protects, and anchors muscles) and clear cornea (lets light in)
Vascular tunic components
choroid: gives blood to all tunics, bw sclera and retina, continuous with ciliary bodies and prevents light scattering
ciliary body: tissue that surrounds lens , anchors suspensory ligaments - keep lens in place
—- ciliary process + muscle controls lens shape
— zonule fibers: coarse hairs that interact with ciliary processes and control lens
iris : coloured part that lets light in, responds to emotions (dilate if appealed)
How does the pupil/ iris change in response to light
Close/bright; pupils constrict + iris closes via sphincter pupillae muscle (controlled by parasympathetic)
far/dim light: pupil opens more and iris gets smaller, controlled by dilator pupillae, pulls pupil down
Sensory tunic
RETINA : has all the photoreceptors
Back layer: pigmented epithelia cells: act as phagocytes to remove dead and damaged photoreceptors, not photosensitive
Transparent inner neural layer: include bipolar, ganglia, amacrine and photoreceptors (photoreceptors —- than bipolar than ganglia; from B to F)
path of light: will hit ganglia first
T or F: there are more ganglia than rods and cones
F - most rods/cones
Function of ganglia in retina
reception from bipolar cells —- have axons that go along eye surface and converge at optic disc at back of eye + leave at optic nerve
- optic nerve: and central artery and vein of retina leave together
What is the only space with out BV
macula lutea: area with highest sensation for colour and crispest image
What is AMD and the types
- degeneration of macule lutea: less quality or crisp image
Dry AMD: lose pigmented epithelia, destroy macula, loss central focus
Wet AMD: affected by choroid and BV, abnormal growth of BV === lose macula
What is retinopathy
found in diabetes
- artery and vein walls get weak and hemorrhage === blindness
- get bleeds that block photoreceptors /light
clots held in place by vitreous humour
What are the two segments of the eye
Posterior: behind lens, filled with vitreous humour, not constantly changing in volume , allow light transmission
Anterior segment: has 2 chambers
- anterior: bw cornea and iris
- posterior : bw iris and lens
Anterior chamber of the anterior segment function
contains aqueous humour, produced by the ciliary process (made in posterior segment)
—aqueous humour drains via scleral venous sinus ; helps support and remove waste
— control IOP (what holds the neural retina against pigmented layer *
continuously made and removed
What is glaucoma
disease to the optic nerve
- when there is damage to the axons of ganglia —- blind spots develop
- brain compensates until big damage
- pressure at back of eye (IOP) increases and causes damage to axons — won’t get input from that area
*aq humour doesn’t flow through trabecular meshwork ; gets blocked and increase IOP
Lens : what is is and function
biconvex, flexible and avascular
fxn: allows precise focusing onto retina
- made of epithelium and lens fibers
Parts of Lens and function
Lens epithelium: cells that differentiate into fibers, make crystalline
Lens fibers: cells filled with crystalline (transport protein)
*as your age: these get more compact and less elastic, can’t focus on close shit
cataracts : clumps of crystallin
Changing of lens shape
controlled by ciliary muscles attached to lens via zonules
focusing far: muscles relax and flatten
focusing close: ciliary muscles contract —- lens gets more biconvex
What wavelength of light can we detect
400-700nm
Difference between convex and concave lens
convex: converge light
concave: spread light
Path of light when it goes through
cornea, aqueous humour, lens, Vitreous humour, neural layer to photoreceptors
Where is light all refracted
cornea, entering lens, and leaving lens
Changes to image when brought in
flipped on horizona. and vertical plane, and shrinks image
Fovea
in macula (center of visual field)
- is the sharpest vision (high cones)
—- most clear and sharpest vision
—- a lot of cones —- colour vision
Focusing on a distant
need little adjust — light rays are already parallel
- don’t change lens shape if more than 6m away
sympathetic: dilate eye + relaxation of ciliary muscles to see
What happens to the rods and cones in a bright room
rods; inactive and saturated
cones: all active
Focusing close
ACC
1) accommodation : change lens shape via ciliary muscles — more convex lens
2) constriction : sphin. pupillary reflex constricts pupils to prevent divergent light from getting in (parasympathetic)
3) Convergence; medial rotation of eyeballs
Myopic eye
can’t see far
- eyed elongated, need to push focal point further back — diverge light more
Correction: concave lens
Hypertonic eyes
can’t see close
eye shorter, need to bend light more to move focal point more forward
Correction: convex lens
Rods
sensitive to dim light , not colour —- lower quality so fuzzy
- ## lower resolution because 1 ganglia —— comes from many rod cells (convergence - don’t know which rod detected what)
Basic structure of rods/cones
interact with pigmented epithelium —- phagocyte old discs from rods/cones
- outer segment : interacts with epithelium, has visual pigments (rhodopsin ) inside the discs
inner segment: has the organelles
synaptic - interact with bipolar
What is retinal
visual pigment in membrane discs in rods/cones
- absorbs light
- combines with opsin to make rhodopsin —- visual pigment
- Vit A makes retinal
- has 2 forms: 11-cis and all trans
What happens to rhodopsin in presence of light
absorbs light —- which converts all the retinal to all-trans (activation of optic nerve)
—- releases opsin
— 11 trans retinal is recycled in the retinal pigmented epithelium into 11-cis to be reused
T or F: there is 4 types of cones
F - 3 types
— each detect specific colours/wavelengths
- detect colour
- no conversion of cones - 1 cone- 1 ganglia
- higher amount in fovea and macula —- gives higher detail but need bright light
Steps to phototransduction : Dark
Rhodopsin: inactive because in 11-cis form only —- doesn’t activate PDE (no conversion of cGMP to GMP) —- increase levels of cGMP —— cause ion channels on photoreceptors to open
—- depolarization of cell: tonic release of Inhibitory neurotransmitters to bipolar ——- turns bipolar off + doesn’t release neurotransmitters to ganglia
——- no activation of ganglia
Photoreceptor releases more neurotransmitters (IPSP) —— turns bipolar off + doesn’t release EPSP - ganglia not activated
Phototransduction: Light
Rhodopsin bleached (converts all to trans retinal) —- activates transducin —- activates PDE to convert cGMP to GMP—- remove cGMP from ion channels (closes them)
—- decrease cGMP — close channels and photocell hyperpolarizes (doesn’t release IPSP) —— bipolar active —- release EPSP to ganglia
- recovery: opsin and retinal recombine to rhodopsin —- inactive *
T or F: Cones and rods are activated by light
F- deactivated —- don’t release neurotransmitter that inhibits bipolar
Adaptation
Bright light: involved decrease retinal sensitivity — rod fxn lost , switch from rod to cone system (takes a bit )
Dark: cones switch to rods system; rhodopsin accumulates with trans
On center off surround fields
stimulated by light hitting center, inhibited by light hitting periphery
Off center on surround field
light inhibits when hits center, stimulated when light hits periphery
Path of visual after leaves eye
optic nerve—- optic chiasm (crossing over occurs) —- optic tract — converge at LGN —- go to visual cortex of occipital lobe
Important of crossing over occurring in optic chiasm
gives depth perception and 3D
— R sides of eyes —- R LGN
— L sides of eyes : left LGN
ONce in the LGN , where can the info be sent
visual cortex
midbrain- eye movement control
SCN- help with info processing, hypothalamus — controls response
