exam 2 study guide #6

Question 1

Which photoreceptor is responsible for night (low acuity, low light threshold) vision?

Answer 1

Rods

Question 2

Which photoreceptor is responsible for color (high acuity, high light threshold) vision?

Answer 2

Cones

Question 3

The relative concentrations of cones is greater in the _____ than the _____ of the retina.

Answer 3

fovea; periphery

Question 4

The relative concentrations of rods is greater in the _____ than the _____ of the retina.

Answer 4

periphery; fovea

Question 5

The fovea:

Answer 5

-provides the area of greatest acuity
-is where we direct our focus when trying to view an object
-is the area where the four layers of accessory neurons and blood vessels are “pulled to the side”
-allows light to directly stimulate the cones

Question 6

The site where the optic nerve and blood vessels leave the retina:

Answer 6

-is the blind spot
-has no photoreceptors

Question 7

What two factors determine the refractive power of a lens?

Answer 7

-the angle at which light enters a lens
-the difference in the refractive indices of the two media

Question 8

The interface which produces the most refraction of light in the normal eye is

Answer 8

air-cornea

Question 9

List the four components of the refractive system of the eye in order from the air to the retina.

Answer 9

-cornea
-aqueous humor
-lens
-vitreous humor

Question 10

Which of the four components of the eye’s refractive system is not fixed and can change its refractive power as needed?

Answer 10

lens

Question 11

focal point

Answer 11

point at which light converges behind a lens

Question 12

focal length

Answer 12

distance between the lens and the focal point

Question 13

convex lens

Answer 13

-lens that causes light rays to converge
-positive diopter

Question 14

concave lens

Answer 14

-lens that causes light rays to diverge
-negative diopter

Question 15

calculating refractive power in diopters

Answer 15

take 1000 and divide by focal length

Question 16

Which of the following are associated with emmetropia?

Answer 16

-focal point on the retina
-focal length = 17mm
-refractive power of lens system = 59 diopters

Question 17

What three reflexes are associated with the near response?

Answer 17

-accommodation
-pupillary
-convergence

Question 18

What does the accommodation reflex do to the refractive power of the eye lens?

Answer 18

increase

Question 19

Contraction of the ciliary muscle is the result of

Answer 19

increased PANS`

Question 20

Relaxation of the ciliary muscle is the result of

Answer 20

decreased PANS

Question 21

What type of muscle is the ciliary muscle?

Answer 21

multi-unit smooth

Question 22

Light rays entering the eye from a distant source are____, while light rays from near sources are _____.

Answer 22

parallel; diverging

Question 23

Ciliary muscles _____ for distant vision, and _____ for near vision.

Answer 23

relax, contract

Question 24

The near point of vision

Answer 24

-increases with advancing age
-changes as the lens loses elasticity

Question 25

Where is the focal point for near vision (with respect to the retina) in uncorrected presbyopia?

Answer 25

behind the retina

Question 26

Where is the focal point for near vision (with respect to the retina) in uncorrected presbyopia?

Answer 26

convex spherical

Question 27

The pupillary reflex is:

Answer 27

-apart of the near response
-involves pupillary constriction occurring simultaneously with the accommodation reflex.
-helps improve the acuity of near vision by reducing the divergent light rays from the near source.

Question 28

What Autonomic Nervous System activity is responsible for active pupillary dilation?

Answer 28

increased SANS

Question 29

What Autonomic Nervous System activity is responsible for active pupillary constriction?

Answer 29

increased PANS

Question 30

What type of muscle is found in the iris?

Answer 30

multi-unit smooth muscle

Question 31

The convergence reflex:

Answer 31

-focuses the image on the fovea of both eyes
-prevents double vision

Question 32

Which of the following are associated with hyperopia?

Answer 32

-focal point behind the retina
-focal length> 17mm
-refractive power of lens system
-corrected with positive diopter lens
-corrected with convex lens

Question 33

Which of the following are associated with myopia?

Answer 33

-focal point in front of the retina
-focal length
-refractive power of lens system> 59 diopters
-corrected with negative diopter lens
-corrected with concave lens

Question 34

How is correction of hyperopia accomplished?

Answer 34

by adding to the refractive power of the eye’s refractive system therefore shortening the focal length so the focal point falls on the retina

Question 35

How is correction of myopia accomplished?

Answer 35

by reducing the refractive power of the eye’s refractive system therefore extending the focal length so that the focal point falls on the retina

Question 36

Astigmatism is the result of:

Answer 36

a difference in refractive power in one or more axes of the refractive system

Question 37

What are two potential causes of astigmatism?

Answer 37

-irregularly shaped cornea
-irregularly shaped lens

Question 38

A spherical lens has a _____focus, while the cylindrical lens has a _____ focus.

Answer 38

point; line

Question 39

A spherical lens focuses light in _____, while the cylindrical lens focuses light in____.

Answer 39

all axes; one axis