Vision

Question 1

2 essential functions of the eye

Answer 1

1) focus light on the retina (accomplished by concerted efforts of the cornea + lens)
2) transduction of light energy into action potentials (accomplished by the retina)

Question 2

anterior chamber of the eye

Answer 2

space between cornea and iris

Question 3

posterior chamber of the eye

Answer 3

space between the zonule fibers (lens) and the back of the iris

Question 4

vitreal cavity of the eye

Answer 4

large space behind the lens, occupies by the vitreous body

Question 5

sclera of the eye

Answer 5

fibrous cover of eye (white of the eye)

Question 6

cornea of the eye

Answer 6

window into eye; clear covering; main refractive elements

Question 7

iris of the eye

Answer 7

forms pupil

Question 8

aqueous humor of the eye

Answer 8

*blood-derived, acellular fluid
*pressurizes the eye + maintains eye shape
*produced by CILIARY BODY
*flows from posterior chamber to anterior chamber

Question 9

zonule fibers of the eye

Answer 9

ligaments that suspend the lens

Question 10

ciliary body of the eye

Answer 10

consists of ciliary processes and ciliary muscle

Question 11

ciliary muscles of the eye

Answer 11

control the shape of the lens

Question 12

choroid of the eye

Answer 12

blood supply plexus serving outer retina, ciliary body, and iris

Question 13

fovea of the eye

Answer 13

*area near central retina with a high concentration of photoreceptors (CONES ONLY)
*foveal pit: unobstructed light path

Question 14

optic nerve of the eye

Answer 14

axons of retinal ganglion cells exiting the retina

Question 15

blood supply of the eye

Answer 15

*provided by 2 branches of the ophthalmic artery:
1. central retinal artery
2. long and short posterior ciliary arteries

Question 16

central retinal artery

Answer 16

*supplies blood to the inner retina
*enters via the optic nerve
*branch of ophthalmic artery

Question 17

long and short posterior ciliary arteries

Answer 17

*form the choroid plexus between the sclera and the retinal pigment epithelium
*supplies blood to the outer retina, ciliary body, and iris
*branch of ophthalmic artery

Question 18

how does the lens get nutrients

Answer 18

aqueous humor

Question 19

how does the cornea get nutrients

Answer 19

relies on the tear film for oxygen, nutrients, and disposal of metabolic wastes

Question 20

why are the lens and cornea not innervated by blood supply

Answer 20

maximizes image clarity

Question 21

emmetropia

Answer 21

normal vision, in which light is focused at the level of the retina

Question 22

hypermetropia / hyperopia

Answer 22

*far-sightedness
*when light is focused BEHIND the retina (light goes too far) due to abnormal eye shape (too short) or not enough refractive power

Question 23

myopia

Answer 23

*nearsightedness
*when light is focused IN FRONT OF retina (light is too near), due to abnormal eye shape (too long) or too much refractive power by cornea and lens

Question 24

correction for myopia

Answer 24

concave lens

Question 25

2 functions of cornea

Answer 25

1) refraction 2) protection

Question 26

refractive function of the cornea

Answer 26

*curvature of cornea accounts for majority of refractive power *layers are optimized for transparency *avascular to prevent blood vessels from obstructing the primary light path

Question 27

protective function of the cornea

Answer 27

*tight junctions in the epithelial layer form a barrier that is impermeable to chemicals and other potentially damaging agents *highly innervated (mostly nociceptive) by CN V1

Question 28

function of the lens

Answer 28

***refraction for accommodation:** -fine focus mechanism -refractive power depends on shape (spherical = higher power = near objects; flattened = lower power = far objects)

Question 29

what happens in the eye when the lens is not accommodated

Answer 29

***ciliary muscles are RELAXED** *zonule fibers are taught ***lens is FLATTENED**

Question 30

presbyopia

Answer 30

loss of ability to accommodate as we age

Question 31

accommodation innervation

Answer 31

1) Edinger-Westphal nucleus (preganglionic parasympathetics) 2) ciliary ganglion -> short ciliary nerves 3) ciliary muscle and pupillary constrictor

Question 32

what produces the aqueous humor

Answer 32

ciliary body

Question 33

what is path of flow of aqueous humor

Answer 33

*flows from point of origin in posterior chamber -> anterior chamber ***exits the eye** to join the venous circulation of the sclera by way of the **trabecular network and the Canal of Schlemm**

Question 34

glaucoma

Answer 34

*usually occurs when the aqueous humor cannot drain, causing **increased intraocular pressure** and putting pressure on the optic nerve head, leading to degeneration of the nerve *impairment of PERIPHERAL vision

Question 35

9 layers of the retina

Answer 35

1. retinal pigment epithelium 2. photoreceptor outer segment 3. photoreceptor inner segment 4. outer nuclear 5. outer plexiform 6. inner nuclear 7. inner plexiform 8. ganglion cell 9. nerve fiber

Question 36

retinal pigment epithelium (layer of the retina)

Answer 36

*forms the blood-retinal barrier *provides metabolic support of outer retina

Question 37

photoreceptor outer segment (layer of the retina)

Answer 37

*contains light-sensitive elements (rods and cones)

Question 38

photoreceptor inner segment (layer of the retina)

Answer 38

synthetic machinery of the photoreceptors

Question 39

outer nuclear (layer of the retina)

Answer 39

photoreceptor cell bodies

Question 40

outer plexiform (layer of the retina)

Answer 40

a layer of synapses between photoreceptors and intraretinal relay neurons

Question 41

inner nuclear (layer of the retina)

Answer 41

cell bodies of relay neurons

Question 42

inner plexiform (layer of the retina)

Answer 42

synapses of relay neurons to ganglion cells

Question 43

ganglion cell (layer of the retina)

Answer 43

cell bodies of the ganglion cells

Question 44

nerve fiber (layer of the retina)

Answer 44

axons of the ganglion cells, which come together at the optic nerve head to exit the eye as the optic nerve (CN II)

Question 45

cones

Answer 45

photoreceptors specialized for vision in bright light (specialized for COLOR)

Question 46

rods

Answer 46

photoreceptors specialized for dim-light vision

Question 47

macular degeneration

Answer 47

affects the fovea (impairment of CENTRAL vision)

Question 48

ascending visual pathway (from retina to primary visual cortex)

Answer 48

1) axons of the retinal ganglion cells exit the retina and form the optic nerve 2) optic nerve partially decussates in the optic chiasm to form the optic tract 3) axons synapse in the LGN of the thalamus 4) from LGN, axons project to the primary visual cortex (above and below the calcarine fissure)

Question 49

visual cortex on the right side of the brain represents what visual space?

Answer 49

LEFT half of visual space

Question 50

axons in the nasal retina...

Answer 50

*receive light from IPSILATERAL visual space *cross in optic chiasm *reach the CONTRALATERAL LGN

Question 51

axons in the temporal retina

Answer 51

*receive light from CONTRALATERAL space *do NOT cross *project to the LGN on the same side

Question 52

retinotopic map of visual cortex

Answer 52

*superior visual space (inferior retina) is mapped below the calcarine fissure *inferior visual space (superior retina) is mapped above the calcarine fissure *central visual space is represented most posteriorly *peripheral visual space is represented more anteriorly *central vision is represented in a disproportionately large amount of cortical tissue

Question 53

monocular visual loss

Answer 53

lesion of an optic nerve causes no sight from that eye

Question 54

bitemporal hemianopia

Answer 54

***lesion of the optic chiasm** *affects the nasal retina of both eyes, causing **loss of both temporal visual fields** *a **pituitary tumor** could cause this

Question 55

macular sparing

Answer 55

vision is spared in the parafoveal region due to the amount of neural tissue devoted to central visual space (because lesions are rarely extensive enough to obliterate the magnified cortical representation of central vision)

Question 56

contralateral homonymous hemianopia

Answer 56

***one half of visual space** (example, left temporal and right nasal) **vision is lost** *can be caused by **lesion of optic tract, optic radiation** (fibers from LGN to visual cortex), or **primary visual cortex** (upper and lower)

Question 57

what happens in the eye when the lens is accommodated

Answer 57

***ciliary muscles are CONTRACTED**, causing the muscle to bulge out *zonule fibers slack ***lens is SPHERICAL**

Question 58

correction for hypermetropia / hyperopia

Answer 58

convex lens