17 Vision 1

Question 1

The cornea of the eye is contiguous with which structure that provides a tough, normally inelastic collagen covering on the eye?

Answer 1

the sclera

Question 2

Where is the anterior chamber and what does it contain?

Answer 2

between cornea and iris, contains a clear watery aqueous humor (this fluid is recycled throughout lifetime)

Question 3

As adults age, what happens to the shape of the lens?

Answer 3

becomes more spherical and less disc-shapped which results in more difficulties with accommodation (reading glasses)

Question 4

What are the functions of the ciliary body?

Answer 4

connects lens to scleral wall, contains muscle and secretory epithelium which manufacture aqueous humor and under neural control it affects the shape of the lens

Question 5

What is the most important function of the vitreous chamber?

Answer 5

the optically empty gel of hyaluronic acid molecules which supports retina layer against the scleral wall

Question 6

What are the names of the neural and vascular layers that line the inside of scleral wall.

Answer 6

retina (neural) and choroid (vascular)

Question 7

Collection of retinal nerve cells actions transmit info to the ____ ____ ____ by way of the optic nerve, optic chasm and optic tract. (sheath continuous with the CNS dura mater.

Answer 7

LGB- lateral geniculate body

Question 8

Light traveling toward the retina is refracted the most between what two layers (these layers have the greatest difference in refraction index)

Answer 8

between the air and the tear film (the tear film/ air interface causes the greatest refraction)

Question 9

If the tear film interface creates the most refraction, what is the purpose of the lens in creating an image on the retina?

Answer 9

lens has the ability to accommodate to focus on far or near objects

Question 10

How do ciliary muscles cause accommodation of lens?

Answer 10

ciliary muscle contractions means contraction of the sphincter muscle which creates less outward pull on the lens, allowing it to round (allows near objects to be focused) NOTE: the difference in shape during accommodation is very small

Question 11

What types of nerves control accommodation?

Answer 11

parasympathetic fibers in the following pathway: Edinger-Westphal nucleus, CN III, ciliary ganglion (synapse), ciliary nerve, ciliary muscle

Question 12

What are emmetropia, hyperopia and myopia respectively?

Answer 12

emmetropia (focusing power matches eye) hyperopia (farsightedness) and myopia (nearsightedness) **length of eye is too long

Question 13

What muscle and general nervous system is responsible for pupil constriction?

Answer 13

sphincter papillae (circular muscle): under parasympathetic control (EW to CNII etc)

Question 14

What muscle and general nervous system is responsible for pupil dilation

Answer 14

dilator pupillae (radial muscle) under sympathetic control (via lateral horn of cervical ganglion to ciliary nerve)

Question 15

What general types of pharmacological agents are used in combination for eye dilation?

Answer 15

encourage dilation with sympathetic agonist (ie. epinephrine) and parasympathetic antagonists (ie. atropine, tropic amide)

Question 16

What are the 4 types of retinal cell types to know?

Answer 16

retinal pigment epithelium, rods/cones, interneurons, and ganglion cells

Question 17

What is the purpose of pigment epithelium?

Answer 17

support photoreceptors, absorb light and heat (analogy of burning ants)

Question 18

What are the function of rods and cones?

Answer 18

change light energy to synaptic energy

Question 19

What is the role of interneurons in the retina?

Answer 19

the relay, process, modify image signals within the retina (begin processing of images still within retina)

Question 20

Why is the retina structure considered “inverted”

Answer 20

photoreceptors are deep to the nerve ganglia on the surface of the retina, photoreceptors also have metabolic needs that are addressed by their close contact with the base of the retina

Question 21

What is the function of ganglion cells in the retina?

Answer 21

relay, process, modify images signals to the brain

Question 22

Compare and contrast the functions of cones and rods

Answer 22

rods are very sensitive, found in in the periphery of the center, cones require a lot of ambient light but they convey color vision found centrally and in low ratio to interneurons/ganglia (1:1 often)

Question 23

What does the tern retinotopic map mean?

Answer 23

signal messaging that conveys a “map” the visual input to the eye is preserve in the sense that signals travel relative to each other in the same pattern from the eye through the nerve

Question 24

Why is the foveal pit in the shape of a depression?

Answer 24

the ganglion and bipolar cells are brushed aside from the center of the pit

Question 25

Where do you find the optic disk/ nerve: on the nose or temporal side?

Answer 25

nose side (medially)

Question 26

T/F the fovea is contained within the area of the macula lutea

Answer 26

T

Question 27

How many types of color receptors are found in the human retina?

Answer 27

3

Question 28

Where do the axons of ganglion cells travel as they exit the retina?

Answer 28

the gather in the optic nerve (organization of signal travels in orderly grouping to preserve the visual map- systematic transfer of information)

Question 29

Describe the pathway of the temporal field of the right eye.

Answer 29

temporal view is projected onto the nasal side of the retina and nasal fibers project back and cross at the chiasma and then back into the left cortex

Question 30

Do nasal or temporal FIBERS from the retina cross?

Answer 30

nasal fibers (carrying image from the temporal side) cross the midline

Question 31

Lesion to the chiasma would affect what part of the visual field?

Answer 31

the temporal of each side

Question 32

How are the fibers exiting the geniculate nucleus further divided topographically as they head toward the occipital cortex?

Answer 32

calcimine sulcus divides the information from inferior eye field to superior cortex and superior visual field to inferior cortex