Lecture 16/17: Vision

Question 1

Cornea

Answer 1

Thick inelastic collagen Outer wall of eye Clear Fibers are parallel

Question 2

Sclera

Answer 2

Thick inelastic collagen Opaque Randomly oriented fibers

Question 3

Anterior Chamber

Answer 3

Between cornea and iris Clear watery aqueous humor

Question 4

Iris

Answer 4

Vascular muscular diaphragm Has the pupil Controls diameter of pupil which is under neural control

Question 5

Lens

Answer 5

Refracts light Optically clear and flexible

Question 6

Ciliary Muscle

Answer 6

Connects lens to scleral wall Affects shape of lens Independent of iris/pupil

Question 7

Vitreous Chamber

Answer 7

Optically empty inner cavity of eye Forces retina to remain in place against sclera

Question 8

Retina and Choroid

Answer 8

Neural and vascular layers lining the inside of the scleral wall

Question 9

Optic Nerve

Answer 9

Collection of retinal nerve axons Transmits information to optic chiasm, then optic tract, lateral geniculate body

Question 10

Hyaloid Canal

Answer 10

Potential structure Tube left over from embryo when eye starts as tube

Question 11

Where is the largest amount of refraction in the eye?

Answer 11

Air-Tear interface

Question 12

Accomodation

Answer 12

Change of lens shape to change focus

Alters refractive power of lens

Question 13

Natural state of the eye lens

Answer 13

Round Ciliary muscle contracts to let the lens be more round

Question 14

Control of Accomodation

Answer 14

Edinger-Westphal nucleus CN III Ciliary ganglion Ciliary Nerve Ciliary Muscle

Question 15

How does the eye achieve an increased depth of field?

Answer 15

Constricts the pupil

Question 16

Sphincter Pupillae

Answer 16

Circular muscle: Constricts pupil size Parasympathetic control Pathway: 1. EW 2. CN III 3. Ciliary ganglion 4. Ciliary Nerve 5. Sphincter

Question 17

Dilator Pupillae

Answer 17

Increases pupil size Sympathetic control Pathway: 1. Lateral Horn 2. Cervical Ganglion 3. Ciliary Nerve 4. Dilator muscle

Question 18

What occurs when the pathway to the Dilator Pupillae is interrupted?

Answer 18

Horner’s Syndrome

Question 19

Sympathetic Agonist that dilates pupil

Answer 19

Epinephrine and congeners

Question 20

Parasympathetic Agonist that contricts the pupil

Answer 20

Acetylcholine Pilocarpine

Question 21

Parasympathetic Antagonist that dilates the pupil

Answer 21

Atropine Homatropine Cyclopentolate Tropicamide

Question 22

Retinal Pigment Epithelium

Answer 22

Supports photoreceptors Absorbs light and heat to prevent damage

Question 23

Rods and Cones

Answer 23

Change light energy to synaptic energy

Question 24

Interneurons

Answer 24

Relay, process, and modify image signals within retina

Question 25

Ganglion cells

Answer 25

Relay, process, and modify image signals TO BRAIN

Question 26

Rod Cells

Answer 26

No color perception Great numbers in periphery, little in center Very sensitive: Perhaps 1000 rods to one ganglion cell

Question 27

Cone cells

Answer 27

Color vision Insensitive Located mostly in central retina Often 1:1 connections to interneurons which allows detail

Question 28

Peripheral Retina

Answer 28

Rods only Lots of rods per ganglion cell Very sensitive No color Image locator

Question 29

Central Retina

Answer 29

Cones mostly Usually 1:1 with ganglion cell Image resolution/analysis

Question 30

Why does color blindness come about?

Answer 30

A type of cone cell is missing a pigment

Question 31

Nerve path from lateral eye to optic nerve

Answer 31

Up and around

Question 32

Deficit observed if lesion

Answer 32

1. No right eye vison 2. Same as 1 3. Both temporal sides 4. No left side vision

Question 33

Optic Chiasm

Answer 33

Inputs from both eyes are organized and overlaid Right and Left fields become joined Fibers from nasal retina cross

Question 34

What vision deficits would occur?

Answer 34

A. Blindness of ipsilateral eye B. Bitemporal or Heteronymous hemianopsia C. Unilateral nasal hemianopsia D. Homonymous hemianopsia E. Upper quadrant hemianopsia F. Lower quadrant hemianopsia

Question 35

Pupillary Light Reflex Pathway

Answer 35

1. Retinal/Ganglion Cells 2. Optic Nerve 3. Optic Chiasm 4. Optic Tract 5. Skips LGN 6. Pretectal Nucleus

Question 36

Pupillary Light Processing Center

Answer 36

Inputs bilateral Output to Edinger Westphal is bilateral Summation and Averaging

Question 37

Pupillary Light Reflex Efferent Pathway

Answer 37

1. Edinger-Westphal Nucleus 2. CN III 3. Ciliary Ganglion in orbit 4. Ciliary Nerves through sclera 5. Pupillary Sphincter

Question 38

Posterior Chamber

Answer 38

Area between the iris and the lens

Question 39

Ciliary Body

Answer 39

Produces aqueous fluid at lateral edge of posterior chamber

Question 40

Canal of Schlemm

Answer 40

Aqueous fluid passes through here to be resorbed If blocked, can cause increased pressure

Question 41

Zonule fibers

Answer 41

Suspend the lens from the peripheral ciliary body

Question 42

What does the eye naturally focus on?

Answer 42

Things farther than 20 feet away

Question 43

What happens when the ciliary muscle contracts

Answer 43

Since it is circular muscle fibers, the diameter will get smaller and relax the zonule fibers, letting the lens become more round

Question 44

What controls the ciliary muscle?

Answer 44

Parasympathetics via EW nucleus

Question 45

If everything is normal, what happens when you shine light in one eye?

Answer 45

Both pupils will constrict

Question 46

Light test: R eye doesn't constrict with ipsilateral light Constricts with contralateral light

Answer 46

Only the optic nerve of the R eye is damaged

Question 47

Light test: The R eye doesn't constrict with light in either eye The L eye still constricts with light in both eyes

Answer 47

Oculomotor nerve/nucleus of the R eye is damaged

Question 48

Mueller's Muscle

Answer 48

Smooth muscle that helps open the upper eyelid Disabled in Horner's Syndrome

Question 49

What are the two different layers of the retina?

Answer 49

Nuclear- cell bodies Plexiform- Axons and dendritic processes

Question 50

What are the four layers of the retina specifically called?

Answer 50

1. Starting from outer 2. Photoreceptor Layer- light transducing cells 3. Interneuron layer 4. Ganglion cell layer- cell bodies 5. Nerve fiber layer- axons to the optic nerve

Question 51

Optic Disc

Answer 51

Place in retina where nerves leave and blood vessels enter the eye

Question 52

Fovea

Answer 52

Half thickness Specialized best acuity in center vision

Question 53

Retinal Pigment Epithelium

Answer 53

Contains melanin Prevents scatter of light and acts as heat sink

Question 54

Where are cone cells greatest in number?

Answer 54

Fovea; center

Question 55

Where are rods greatest in number?

Answer 55

Perifovea, periphery

Question 56

Rhodopsin

Answer 56

Pigment in rods Only indicates presence or absence of light

Question 57

Lamina Cribrosa

Answer 57

Barrier where the optic nerve leaves the eye that separates CSF from fluid in the eye

Question 58

Where do ganglion cells first become myelinated?

Answer 58

When they leave the eye Myelin absorbs light

Question 59

Optic tract

Answer 59

Optic nerves after they have passed through the optic chiasm

Question 60

Lateral Geniculate Body

Answer 60

Left sees right and vice versa Topographically aligns retinal projections Segregates visual signals Gateway that controls signals to cortex

Question 61

Other names for Primary Visual Cortex

Answer 61

1. V1 in occipital lobe 2. Area 17 3. Stria of Gennari 4. Striate Cortex 5. Calcarine Cortex

Question 62

Describe the light reflex for a damaged right optic nerve

Answer 62

Question 63

Describe the light reflex for a damaged right oculomotor nerve

Answer 63