ACCOMMODATION FC1

Question 1

Accommodation is a dynamic process to produce and maintain a

Answer 1

focused retinal image

Question 2

The power of the lens changes to

Answer 2

maintain the image

Question 3

What are the three components of the lens that change?

Answer 3

The lens curvature changes, the lens power changes and focusing changes.

Question 4

There is a change in the shape which leads to a change in

Answer 4

the power of the lens

Note: This allows objects at various distance to be focused at the retina

Question 5

The only active element is

Answer 5

the ciliary muscle, while other parts are

passive

Question 6

1-Ciliary muscle contracts →

Answer 6

pulls the ciliary ring forward & inward → which stretches the choroid & posterior zonules → this yields a rounded lens and
capsule.

Question 7

2- Ciliary muscle contracts →

Answer 7

anterior zonules reduce their tension and relax → reducing the pull on the lens

Question 8

When the ciliary muscle relaxes

Answer 8

the passive restoring force of the spring-like

choroid and posterior zonules return to their original position

Question 9

Ciliary muscle is a ________ muscle with__________

Answer 9

smooth, parasympathetic

Question 10

In accommodation, the ciliary muscle in the

ciliary body

Answer 10

contracts and moves forward
Note: This contraction releases the resting tension on the zonules around the lens equator. The lens capsule is able to mold the lens to become more spherical.

Question 11

Anterior and posterior capsule is taught and flat when

Answer 11

there is no accommodation

Question 12

Light enters the eye and is focused at________ to give a clear shape______

Answer 12

retina, image

Question 13

the ciliary muscle is relaxed when there is

Answer 13

no accommodation

Question 14

The unaccommodated emmetropic eye focuses on a distant target and
there is

Answer 14

no need for accommodation

NOTE: Convergence demand is zero

Question 15

With a near object (object closer than infinity), the object has_________ that focus behind the eye, leading to an unfocused image on the_______________

Answer 15

Divergent, retina

Question 16

The optical power in the eye has to increase to

Answer 16

add positive convergent rays

Question 17

In the accommodative eye, the image is in focus because of

Answer 17

the accommodating lens

Question 18

The 3 physiological changes seen in accommodation:

Answer 18

Eye accommodation
Pupil constriction
Eyes converge
NOTE: Also known as the near reflex. All of these are coupled neuronally through the parasympathetic innervation from the EW nucleus.

Question 19

The convergence, accommodation and pupil constriction occur in_____________
eye/eyes - even if accommodative stimulus is presented to__________ eye/eyes

Answer 19

both eyes, one eye

Question 20

Change in pupil size

Answer 20

controls light
modifies depth of focus
varies any optical aberration

Question 21

Components of Accommodation

Answer 21

Reflex accommodation
Vergence accommodation
Tonic accommodation
Proximal accommodation

Question 22

Reflex accommodation

Answer 22

An automatic adjustment of the refractive state to maintain a focused
retinal image.Occurs when responding to blur, or a reduction in contrast.
It is a response to a small amount of blur.
This is particularly important for small scanning eye movements or
micro saccades.Very important because it makes the fine change under binocular and
monocular conditions.

Question 23

Vergence accommodation

Answer 23

This is the change in accommodation induced during fusional
vergences. This leads to the convergence accommodation/convergence ratio
(CA/C)

Question 24

Proximal accommodation

Answer 24

The refocusing that occurs due to the apparent (or perceived) nearness
(proximity) of a target. Activated by perceptual cues. Stimulated by targets located within 3 meters of an individual.

Question 25

Tonic accommodation

Answer 25

“Lead of accommodation” The residual/resting level of accommodation due to baseline stable innervation input from the midbrain. The accommodation at rest (0.5D to 1.5D). Present even in the absence of blur, disparity (that requires fusional vergences) and proximal cues. Reduces with age

Question 26

Factors that affect accommodation

Answer 26

``` Blur Convergence Proximal issues Pharmacology Minus lens Diseases Retinal image factors: contrast, spatial frequency, retinal image motion Non retinal factors: mood, voluntary effort, target luminance, training Optical cues: offer information about directionality, astigmatism, aberrations Non optical cues: size, proximity, apparent distance, depth cues ```

Question 27

*Aberrations (an optical cues) occur when

Answer 27

the peripheral rays don’t coincide with | the central and on axis rays

Question 28

*Depth of focus is the

Answer 28

variation/small range in the image distance that is tolerable without a profound defocus. This influences accommodation as it increase.

Question 29

Accommodation is stimulated by

Answer 29

mediated parasympathetic system NOTE: Antagonized best with muscarinic blockers – they prevent acetylcholine from binding.

Question 30

Muscarinic antagonists commonly used in practice:

Answer 30

Tropicamide (Mydriacyl) Cyclopentolate Atropine (iritis) Homatropine Scopolamine They produce mydriasis and loss of accommodation Phenylephrine (adrenaline), a sympathomimetic, causes mydriasis but has no significant effect on accommodation

Question 31

Tropicamide (Mydriacyl)

Answer 31

has a very short half-life and should not be used to determine the cycloplegic refraction.

Question 32

Cyclopentolate

Answer 32

is effective with sufficient half-life, used frequently in peds. USUALLY USED IN CHILDREN

Question 33

Other drugs that affect accommodation

Answer 33

``` Alcohol Ganglion blockers Phenothiazides & antidepressants CNS stimulants Marijuana Carbonic Anhydrase Inhibitors Antihistamines Morphine ```

Question 34

Some conditions that affect accommodation

Answer 34

``` Diabetes Traumatic Brain Injury (TBI) Multiple Sclerosis Myasthenia Gravis Botulism Down syndrome Glaucoma Iritis Iris Sphincter tear Eye trauma Adie’s tonic pupil Encephalitis Syphilis Neuro-ophthalmic lesions ```

Question 35

Presbyopia

Answer 35

Gradual age-related irreversible loss of accommodative amplitude. Reported clinically about 40-45 years of age Complete loss of ability to accommodate by about 50-55 years.About a 2.5D loss of accommodation per year.

Question 36

Complaints of Presbyopia are:

Answer 36

receded near point of accommodation blurred vision discomfort and asthenopia at near.

Question 37

Contributing factors and biochemical changes that lead to the decrease of accommodation:

Answer 37

lens thickness and size increases springiness of capsule decreases (thickens) anterior surface curvature increases stiffer lens ciliary muscle remains stable cortex stiffens zonules become less dense (number of them).

Question 38

The following factors do not change in presbyopia:

Answer 38

zonules still have their elasticity ciliary muscle still functions motor neuronal pathway still functions

Question 39

``` Accommodative Excess (dont need a plus lens) ```

Answer 39

treated with proper distance correction and VT

Question 40

``` Accommodative Infacility (have accommodation, but do not know how to use it, need teraphy) ```

Answer 40

proper correction and vision therapy

Question 41

Accommodative insufficiency

Answer 41

proper distance correction and plus lenses

Question 42

Accommodation Convergence/Accommodation Ratio

Answer 42

Also known as AC/A The amount of convergence induced by a change in accommodation. A change in accommodation is accompanied by a change in vergence Accommodation and vergence permit clear stable single binocular vision across a range of viewing distances.

Question 43

In accommodation, there is_________ | With no accommodation, there is ________

Answer 43

convergence, divergence

Question 44

AC/A ratio helps evaluate the strength between the

Answer 44

e accommodative and vergences systems

Question 45

Abnormal AC/A ratios are seen

Answer 45

in binocular problems

Question 46

2 ways of measuring the AC/A ratio

Answer 46

- Gradient determination | - Near-far (or calculated) determination

Question 47

Calculated near-far AC/A ratio is usually_________ the gradient AC/A because of the proximal vergences that influences the near phoria

Answer 47

larger than

Question 48

A high AC/A ratio means there is___________ with accommodation

Answer 48

excess convergence

Question 49

A low AC/A ratio means there is_______ with accommodation

Answer 49

low convergence