Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Block 3 Clinical Skills > Accommodation > Flashcards

Accommodation Flashcards

1
Q

Why is accommodation important?

A

A dynamic process to produce and maintain a focused retinal image.

The power of the lens changes to maintain the image.
The lens curvature changes, the lens power changes and focusing changes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

The Accommodative Process:
There is a change in the shape which leads to a change in the _____ of the lens. This allows objects at various distance to be focused at the retina.

A

power

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The only ACTIVE element is the _______, while other parts are passive.

A

ciliary muscle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the step to reach a rounded lens and capsule?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the steps to reduce the pull on the lens?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

When the ciliary muscle relaxes, the passive restoring force of the spring-like 1._____ and 2._______ return to their original position.

A
  1. choroid

2. posterior zonules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Ciliary muscle is a smooth muscle with __________ innervation

A

parasympathetic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

In accommodation, the ciliary muscle in the ciliary body contracts and moves 1. _____. This contraction releases the 2._______ tension on the zonules around the lens equator. The lens capsule is able to mold the lens to become more 3. ______.

A
  1. forward
  2. resting
  3. spherical
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the parasympathetic pathway to the ciliary muscle?

A
  1. Unfocused image on the retina
  2. Blur signals transmitted to visual cortex
  3. Cortical cell produce sensory blur signals
  4. Signal goes to midbrain/oculomotor nucleus/Edinger-Westphal nucleus (parasympathetic pathway starts here)
  5. Motor command transmitted to ciliary muscle:
    oculomotor nerve (CN 3) → ciliary ganglion → short ciliary nerve
  6. Ciliary muscle contraction
  7. Crystalline lens deforms to produce an in-focus retinal image
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Parasympathetic Pathway to the ciliary muscle:
Note: This pathway is coupled with pupillary function

  1. _____ image on the retina
A
  1. Unfocused image on the retina
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Parasympathetic Pathway to the ciliary muscle:
Note: This pathway is coupled with pupillary function

  1. Blur signals transmitted to _____
A
  1. Blur signals transmitted to visual cortex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Parasympathetic Pathway to the ciliary muscle:
Note: This pathway is coupled with pupillary function

  1. ______ produce sensory blur signals.
A
  1. Cortical cell produce sensory blur signals.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Parasympathetic Pathway to the ciliary muscle:
Note: This pathway is coupled with pupillary function

  1. Signal goes to _______ (parasympathetic pathway starts here)
A
  1. Signal goes to midbrain/oculomotor nucleus/Edinger-Westphal nucleus (parasympathetic pathway starts here)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Parasympathetic Pathway to the ciliary muscle:
Note: This pathway is coupled with pupillary function

  1. Motor command transmitted to ciliary muscle:
A

oculomotor nerve (CN 3) → ciliary ganglion → short ciliary nerve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Parasympathetic Pathway to the ciliary muscle:
Note: This pathway is coupled with pupillary function

  1. Ciliary muscle contraction
A
  1. Ciliary muscle contraction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Biomechanics of the accommodative process
1. Innervation to the ciliary muscle
2. Ciliary muscle ______
3. Ciliary muscle moves inward and ____
4. Ciliary ring advances approximately ____ mm along with the ciliary muscle
5. Choroid and posterior zonules stretch approximately ___ mm
6. Anterior zonular tension _____, and the zonules relax
7. The lens capsule molds the crystalline lens;
lens becomes more _______
8. Lens power ______ and the focal length ______
9. The eye changes focus from ______ to _____.

A

Biomechanics of the accommodative process
1. Innervation to the ciliary muscle
2. Ciliary muscle contracts
3. Ciliary muscle moves inward and anteriorly/forward
4. Ciliary ring advances approximately 0.5 mm along with the ciliary muscle
5. Choroid and posterior zonules stretch approximately 0.5 mm
6. Anterior zonular tension decreases, and the zonules relax
7. The lens capsule molds the crystalline lens;
lens becomes more round/spherical
8. Lens power increased and the focal length decreases
9. The eye changes focus from distance to near

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Accommodation occurs when the overall power of the lens increases. The following are the changes in the lenses that lead to the increase in power:

  • equatorial diameter decreases from __ to __ mm
  • the anterior lens surface moves anteriorly while posterior surface moves posteriorly
  • central anterior radius of curvature changes from __ to ___ mm (becomes more ____)
  • central posterior radius of curvature decreases from ____ to ____ mm
  • central thickness increases by ____ to ____ mm (at the nucleus)
  • lens sinks ___ mm as a result of gravity
A
  • equatorial diameter decreases from 10 to 9.6 mm
  • the anterior lens surface moves anteriorly while posterior surface moves posteriorly
  • central anterior radius of curvature changes from 11 to 5.5 mm (becomes more steep)
  • central posterior radius of curvature decreases from 5.18 to 5.05 mm
  • central thickness increases by 0.36 to 0.58 mm (at the nucleus)
  • lens sinks 0.3 mm as a result of gravity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Anterior and posterior capsule is _____ and ____ when there is no accommodation

A

Anterior and posterior capsule is taught and flat when there is no accommodation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Light enters the eye and is focused at the retina to give a clear shape image, the ciliary muscle is ____ when there is no accommodation.

A

Light enters the eye and is focused at the retina to give a clear shape image, the ciliary muscle is relaxed when there is no accommodation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

The unaccommodated emmetropic eye focuses on a distant target and there is no need for accommodation
Convergence demand is _____.

A

zero

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

With a near object (object closer than infinity), the object has _____ rays that focus behind the eye, leading to an ____ image on the retina.
The optical power in the eye has to _____ to add positive _______ rays.

A

With a near object (object closer than infinity), the object has divergent rays that focus behind the eye, leading to an unfocused image on the retina.
The optical power in the eye has to increase to add positive convergent rays.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

In the accommodative eye, the image is in focus because of the _______ lens.

A

accommodating lens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Accommodation is measured in Diopters. How do you solve it from cm?

A

First, convert the distance to cm. Then, do 100/__cm.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Accommodation Triad/Near Reflex

The 3 physiological changes seen in accommodation:

A
  1. Eye accommodation
  2. Pupil constriction
  3. Eyes converge

All of these are coupled neuronally through the parasympathetic innervation from the EW nucleus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

The convergence, accommodation and pupil constriction occur in both eyes - even if accommodative stimulus is presented to one eye. So, when there is a change in pupil size, these 3 things happen:

A

Change in pupil size

  1. controls light
  2. modifies depth of focus
  3. varies any optical aberration
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Components of Accommodation are:

A
  1. Reflex accommodation
  2. Vergence accommodation
  3. Tonic accommodation
  4. Proximal accommodation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

An automatic adjustment of the refractive state to maintain a focused retinal image.

A

Reflex accommodation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Reflex accommodation occurs when responding to ____, or a reduction in contrast. It is a response to a small amount of _____.

A

blur

blur

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

Reflex accommodation is particularly important for small scanning eye movements or ________.
Very important because it makes the fine change under binocular and monocular conditions.

A

micro saccades

Microsaccades are a kind of fixational eye movement. They are small, jerk-like, involuntary eye movements, similar to miniature versions of voluntary saccades.

30
Q

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

A

Vergence accommodation

31
Q

Vergence accommodation leads to what ratio?

A

It leads to the convergence accommodation/convergence ratio (CA/C).

32
Q

The refocusing that occurs due to the apparent (or perceived) nearness (proximity) of a target.

A

Proximal accommodation

33
Q

Activated by perceptual cues.

Stimulated by targets located within 3 meters of an individual.

A

Proximal accommodation

34
Q

Tonic accommodation is also called

A

“Lead of accommodation”

35
Q

The residual/resting level of accommodation due to baseline stable innervation input from the midbrain.

A

Tonic accommodation

36
Q

Tonic accommodation at rest is how many diopters?

A

(0.5D to 1.5D)

37
Q

Present even in the absence of blur, disparity (that requires fusional vergences) and proximal cues.
Reduces with age

A

Tonic accommodation

38
Q

Factors that affect accommodation

A 
Blur 
Convergence 
Proximal issues 
Pharmacology 
Minus lens 
Diseases
39
Q

Retinal Image Factors that affect accommodation

A

Retinal image factors: contrast, spatial frequency, retinal image motion

40
Q

Non retinal factors that affect accommodation

A

Non retinal factors: mood, voluntary effort, target luminance, training

41
Q

Optical cues that affect accommodation:

A

offer information about directionality, astigmatism, aberrations

42
Q

Non optical cues that affect accommodation:

A

size, proximity, apparent distance, depth cues

43
Q

Accommodation is sensitive and accommodative errors increase significantly with changes in _____ and ______.

With significant change, accommodative response returns towards tonic (slow) levels.

A

eccentricity and retinal image velocity

44
Q

Accommodation is sensitive and accommodative errors increase significantly with changes in _____ and ______. With significant change, accommodative response returns towards tonic (slow) levels. In real life, these factors are not isolated, so the accommodation has a very robust and healthy way of detecting optimally and discriminating fine details.

A

eccentricity and retinal image velocity

Eccentricity: deviation of a curve or orbit from circularity.

45
Q

Aberrations (an optical cues) occur when the ______ don’t coincide with the central and on axis rays

A

peripheral rays

46
Q

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

A

Depth of focus

47
Q

Accommodation is stimulated by mediated parasympathetic system and antagonized best with _________.

A

muscarinic blockers – they prevent acetylcholine from binding.

48
Q

Muscarinic antagonists commonly used in practice are:

A

Tropicamide (Mydriacyl) and Cyclopentolate

49
Q

Tropicamide (Mydriacyl) but has a _____ half-life and should not be used to determine the _____ refraction.

A

very short

cycloplegic

50
Q

Cyclopentolate is effective with ____ half-life, used frequently in kids.

A

sufficient

51
Q

Which one is used in kids: Tropicamide or Cyclopentolate?

A

Cyclopentolate

52
Q

Others muscarinic include:

A

Homatropine
Atropine (iritis)
Scopolamine

Think: HAS

They produce mydriasis (dilation of the pupil) and loss of accommodation.

53
Q

Phenylephrine (adrenaline), a _______, causes mydriasis (dilation of pupil) but has no significant effect on accommodation.

A

sympathomimetic

sympathomimetic (of a drug) producing physiological effects characteristic of the sympathetic nervous system by promoting the stimulation of sympathetic nerves.

54
Q

Other drugs that affect accommodation

A 
Alcohol 
Ganglion blockers 
Phenothiazides & antidepressants 
CNS stimulants 
Marijuana 
Carbonic 
Anhydrase 
Inhibitors 
Antihistamines 
Morphine
55
Q

Some conditions that affect accommodation

A 
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
56
Q

Presbyopia: Gradual age-related irreversible loss of accommodative amplitude. Reported clinically about 1.____ years of age. Complete loss of ability to accommodate by about 2.____ years.

About a 3.___ D loss of accommodation per year.

A
  1. 40-45
  2. 50-55
  3. 2.5 D
57
Q

Presbyopia complaints are:

A
  1. receded near point of accommodation
  2. blurred vision
  3. discomfort
  4. asthenopia (eye strain) at near
58
Q

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

A
  1. lens thickness and size increases
  2. springiness of capsule decreases (thickens)
  3. anterior surface curvature increases
  4. stiffer lens
  5. ciliary muscle remains stable
  6. cortex stiffens
  7. zonules become less dense (number of them)
59
Q

The following factors do not change in presbyopia:

A
  1. zonules still have their elasticity
  2. ciliary muscle still functions
  3. motor neuronal pathway still functions
60
Q

How is presbyopia treated?

A

Plus lenses are used to treat presbyopia.

It could be form of bifocals, reading glasses, monovision or bifocal contact lenses or even surgical correction.

61
Q

Other accommodative conditions:

These occur in adults and children. As a result of medication, illness or even an accommodative anomaly. Name them.

A

Accommodative Excess
Accommodative Infacility
Accommodative insufficiency

62
Q

Treated with proper distance correction and VT

A

Accommodative Excess

63
Q

Proper correction and vision therapy

A

Accommodative Infacility

64
Q

Proper distance correction and additional plus lenses

A

Accommodative insufficiency

65
Q

What is the Accommodation Convergence/Accommodation Ratio?

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.

In accommodation, there is convergence With no accommodation, there is divergence

AC/A ratio helps evaluate the strength between the accommodative and vergences systems

66
Q

Abnormal AC/A ratios are seen in _____ problems

A

binocular

67
Q

2 ways of measuring the AC/A ratio

A
  • Gradient determination

- Near-far (or calculated) determination

68
Q

Gradient determination of AC/A ratio:

Phoria is measured at the same near distance (40cm), but with different lenses to change the accommodative demand.

Gradient advantage: At the same distance, ________ accommodation is controlled

This can be done in the phoropter or with Modified Thorington, through the _____ refraction (with prisms in phoropter to dissociate to provide an open loop so accommodation is not influenced by any other stimulus)

Remind the patient to keep the near point target clear to maintain accommodation. Have the patient read the letters.

Measure the phoria.

Then measure the phoria again through ___ D lenses added to the refraction.

The difference in prism diopters between the phoria with the _______ and the phoria with the ____ is the change in convergence.

That is – this is how convergence responses to the accommodative stimulus.

A

Phoria is measured at the same near distance (40cm), but with different lenses to change the accommodative demand.

Gradient advantage: At the same distance, proximal accommodation is controlled

This can be done in the phoropter or with Modified Thorington, through the subjective refraction (with prisms in phoropter to dissociate to provide an open loop so accommodation is not influenced by any other stimulus)

Remind the patient to keep the near point target clear to maintain accommodation. Have the patient read the letters.

Measure the phoria.

Then measure the phoria again through -1.00D lenses added to the refraction.

The difference in prism diopters between the phoria with the subjective and the phoria with the -1.00 is the change in convergence.

That is – this is how convergence responses to the accommodative stimulus.

69
Q

What does the formula of the AC/A ratio mean?

A

AC/A = (phoria with minus lenses – baseline phoria) divided by (absolute power of additional minus lenses)

70
Q

Calculated near-far AC/A ratio is usually larger than the gradient AC/A because of the proximal vergences that influences the near phoria.

Near-far/calculated AC/A ratio is:

A

AC/A = PD (cm) + NFD (P’near – P distance)

PD =interpupillary distance in cm
NFD = near fixation distance in meter
P’near = near phoria (eso is plus and exo is minus)
P distance = distance phoria

71
Q

A high AC/A ratio means there is ____ convergence with accommodation A low AC/A ratio means there is _____ convergence with accommodation

A

A high AC/A ratio means there is excess convergence with accommodation A low AC/A ratio means there is low convergence with accommodation

Block 3 Clinical Skills (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions