Optics: Accommodaiton

Question 1

What is accommodation?

Answer 1

The ability of the eye to change its power to bring objects of interest at different distances into focus

Question 2

In the unaccommodated form, the zonules…

Answer 2

Pull on the lens and flatten it

Question 3

When changing focus from far to near vision, the ciliary muscle ______, _________ the tension on the zonules

Answer 3

Contracts, reducing

Question 4

What allows the lens to take on a more round shape?

Answer 4

The elastic properties of the lens capsule

Question 5

Less curvature =

Answer 5

Less power

Question 6

When the eye accommodates, what happens to the anterior surface of the lens?

Answer 6

It moves forward and takes a hyperbolic form

Question 7

What is the amplitude of accommodation (accommodation range)?

Answer 7

The distance between the far and near points

Question 8

What four structures bring about changes in optical power?

Answer 8

-ciliary
-choroid
-zonules
-crystalline lens

Question 9

Changes in lens when going from distant to near target:

Answer 9

-anterior movement of choroid
-ciliary constricts
-zonules loosens
-lens less curved
-optical power increases

Question 10

Changes in lens when going from near to distant target:

Answer 10

-posterior movement of choroid
-ciliary relaxes
-zonules tighten
-lens flattened
-optical power decreases

Question 11

Lens diameter ___________ with accommodation?

Answer 11

Decreases

Question 12

Does lens diameter change throughout life?

Answer 12

No

Question 13

As accommodation occurs, the lens surface curvature becomes _________, lens thickness _________, and anterior chamber ___________

Answer 13

Steeper, increases, decreases

Question 14

Which lens surface has more movement?

Answer 14

The anterior surface

Question 15

Which structure involved in accommodation is the active structure? Where does it get its input?

Answer 15

Ciliary, receives its input from the midbrain

Question 16

The choroid, zonules, and crystalline lens are ________ structures

Answer 16

Passive structures

Question 17

What makes the choroid, zonules, and crystalline lens passive?

Answer 17

The receive their in-out from the ciliary body

Question 18

What is sensory cue to accommodation?

Answer 18

The reference frame used to drive accommodation

Question 19

Two different categories of accommodation cues:

Answer 19

-retinotopic cues
-spatiotpoic cues

Question 20

What are retinotopic cues?

Answer 20

-Retinal blur and binocular retinal image disparity
-the eye is reference for accommodation

Question 21

What are Spatiotopic cues to accommodation?

Answer 21

-Target proximity
-use the entire body area reference to accommodate

Question 22

What is the range for retinotopic accommodation cues?

Answer 22

Smaller and finer ranges

Question 23

What is the optimal stimulus for retinotopic cues?

Answer 23

Near demand

Question 24

How often are retinotopic cues sampled?

Answer 24

Continuously to fine tune the near response

Question 25

What is the operating range of spatiotopic accommodation cues?

Answer 25

Larger and coarser range

Question 26

What is the optimal stimulus for spatiotopic accommodation cues?

Answer 26

Far demand

Question 27

How often are spatiotopic cues sampled?

Answer 27

Intermittently at the beginning of the near response

Question 28

What is blur driven (reflex) accommodation?

Answer 28

The automatic adjustment of the refractive state to maintain and sharp and focused retinal image in response to blur input

Question 29

What assists in blur-driven or reflex accommodation?

Answer 29

Microsaccades, voluntary accommodative effort is also needed

Question 30

What amount of blur is reflex accommodation responsible for?

Answer 30

Up to 2D

Question 31

Which mode of accommodation is the largest and most important component for both monocular and binocular viewing conditions?

Answer 31

Blur-driven (reflex) accommodation

Question 32

What is Disparity-driven (vengeance) accommodation?

Answer 32

Accommodation induced by the instinct to fuse images *second major component

Question 33

Which two modes of accommodation are retinotopic?

Answer 33

-blur-driven (reflex) -disparity-driven (vergence)

Question 34

What is Proximity-driven accommodation?

Answer 34

Accommodation due to the influence or knowledge of apparent nearness of an object (within 3m)

Question 35

What is proximal accommodation stimulated by?

Answer 35

Perceptual cues

Question 36

What is tonic accommodation?

Answer 36

-Seen in the absence of blur, disparity, and proximal inputs -presumably reflects baseline innervation and stable input

Question 37

Range of tonic accommodation

Answer 37

1D

Question 38

Reduced VA at near is correlated with ________________ and reduced VA at far is correlated with _____________

Answer 38

Accommodative lag, accommodative lead

Question 39

Accommodative triad:

Answer 39

-accommodation in both eyes -constriction of pupils -convergence of eyes

Question 40

What does convergence achieve?

Answer 40

Single, fused image of the near object as viewed with both eyes

Question 41

What does constriction of the pupil do?

Answer 41

Increases the depth of field

Question 42

Uncorrected myope must accommodate ________ the emmetrope

Answer 42

Less than

Question 43

Accommodation required by an emmetropic eyes is _________ the stimulus of accommodation

Answer 43

Equal to

Question 44

When an eye is corrected with a contact lens the required accommodation is ________ the stimulus to accommodate

Answer 44

Equal to

Question 45

When an object is located at the far point, will that person be accommodating?

Answer 45

No

Question 46

An uncorrected hyperope must accommodate ___________ the emmetrope

Answer 46

More than

Question 47

An uncorrected myopic patient may continue to…

Answer 47

Have acceptable near vision even as they age and lose the accommodative ability (bc the far point is closer)

Question 48

What is the near point of accommodation?

Answer 48

How near an object can be to the eye and still be imaged clearly on the retina