Motility Disorders: Accommodation And Convergence

Front 1

Define convergence.

Back 1

Process which "moves" the image you see onto the fovea - movement of eyes toward the midline

Front 2

Increase of the dioptric power of the lens to maintain a clear image (focus) when objects are moved. This is defined as?

Back 2

Accommodation

Front 3

(T/F) Miosis improves depth of field.

Back 3

True - since miosis describes when your pupils become smaller

Front 4

What three anatomical events happen while accommodating?

Back 4

1. Ciliary muscle contracts
2. Zonular fibers relax
3. Lens becomes convex (more plus power)

Front 5

The main automatic stimulus to focus (accommodate) is _________.

Back 5

Blur

Front 6

A psychologic stimulus to accommodate is ________________________.

Back 6

Awareness of near

Front 7

What is chromatic aberration?

Back 7

Prismatic effect - separate white light into its component colors

Front 8

The range of accommodation occurs between the ____ and ____.

Back 8

NPA and FPA

Front 9

The point at which no accommodation is exerted is defined as?

Back 9

FPA

Front 10

What is NPA?

Back 10

Near Point of Accommodation - the closest point at which the eyes can effectively accommodate.

Front 11

Why shouldn't a patient wear their near correction when measuring accommodation?

Back 11

It will relax their accommodation - not accurate

Front 12

The basis of accommodative measurement is?

Back 12

NPA

Front 13

What is dynamic retinoscopy and how is it done (brief)?

Back 13

method of assessing accommodative effort
- retinoscopy reflex - how it changes when presented with a near target
- less reflex with accommodation

Front 14

How is Duane's Standard Curve of Accommodation computed?

Back 14

The curve is composed relative to age, and is computed using the rule of 4's as an approximate curve showing accommodative ability.

Front 15

What is the rule of 4's?

Back 15

4*4 - (age)/4

Front 16

What is presbyopia?

Back 16

Normal (natural) recession of NPA with age. Young lens is more plastic and more pliable, stiffens with age. Patient needs 50% of their accommodative ability in reserve in order to be COMFORTABLE.

Front 17

What is accommodative insufficiency? What could cause it?

Back 17

- sometimes caused by medications, trauma, disease
- accommodative ability is reduced for their age.

Front 18

Accommodation is innervated by the __________ nervous system.

Back 18

Parasympathetic (PNS)

Front 19

A patient's accommodative ability is initially normal, but becomes much worse with prolonged effort. What is this defined as?

Back 19

Accommodative Fatigue - can't maintain the same amount of accommodation

Front 20

What is accommodative inertia?

Back 20

Delay in changing the accommodative state from one fixation distance to another.

Front 21

Symptoms such as a sudden onset ET and diplopia are often associated with?

Back 21

Accommodative Spasm

Hint 21

Accommodative deficiency...

Front 22

excessive amount of accommodation (over effort to accommodate) causes an ET. This is defined as?

Back 22

Accommodative spasm

Front 23

What is the result of complete paralysis of accommodation?

Back 23

- inability to focus eyes at near/inability to accommodate
- uni or bilateral
- sometimes associated with CN III

Front 24

What is Accommodative Effort Syndrome?

Back 24

- patient has low fusional divergence amplitudes

Front 25

Disconjugate movement of the eyes toward the midline is denoted as:

Back 25

Convergence

Front 26

Closest point where convergence and BSV can be maintained is denoted as:

Back 26

NPC

Front 27

What units are NPA in? NPC?

Back 27

NPA in Diopters
NPC in MA (meter angle)

Front 28

average NPC is approximately ___ cm.

Back 28

10

Front 29

A patient with NPC 14 cm is asymptomatic.
a) How does their NPC compare to the normal NPC?
b) Does this patient need treatment?

Back 29

a) worse
b) no

Front 30

A patient has NPC 10 cm.

Does the patient need treatment?

Back 30

Yes if symptomatic, no if not.

Front 31

If fixation distance is 0.25 m, what is NPC?

Back 31

4 MA

Front 32

What are the 5 types of convergence?

Back 32

1- Voluntary
2- Tonic
3- Accommodative
4- Fusional
5- Proximal

Front 33

In regard to Voluntary Convergence:
a) How is it measured?
b) Does voluntary convergence decrease with age?

Back 33

a) measured using NPC - generally closer to eyes that NPA
b) no

Front 34

What is the only vergence movement that can be voluntary? (exerted without an external stimulus)

Back 34

Voluntary Convergence

Front 35

What is tonic convergence?

Back 35

The eyes tend to naturally diverge, therefore to remain in orthotropic position, tone must exist in MR muscles.

Front 36

The amount of convergence elicited with a given amount of accommodation is denoted as:

Back 36

Accommodative Convergence - expressed as ratio AC/A

Front 37

What is fusional convergence?

Back 37

convergence stimulated by disparate retinal images (i.e. stay fovea to fovea)

Front 38

The awareness of the nearness of an object is defined as:

Back 38

Proximal Convergence

Front 39

What is Convergence Insufficiency?

Back 39

Inability to maintain binocular convergence without effort

Front 40

Chavasse's Classification is used for:

a) Accommodative Anomalies
b) Measurement of NPA
c) Convergence Anomalies
d) Measurement of NPC

Back 40

c) Convergence anomalies

Front 41

Describe a convergence paralysis.

Back 41

- crossed diplopia at near
- normal adduction
- unable to converge
- exo at near

Front 42

This anomaly occurs almost exclusively in hysteric or neurotic patients. Intermittent maximal convergence with accommodative spasm and miosis.
What is this anomaly?

Back 42

Convergence spasm

Front 43

When to measure AC/A ratio?

Back 43

- Accommodative Eso - Convergence Excess
- Intermittent Exo - Divergence Excess (determines true or pseudo)

* significant difference in deviation at near/distance *

Front 44

Use the Heterophoria method to calculate the AC/A ratio with the following data.

IPD = 6 cm
1/3 m = ET 16
6m = ET 6

Back 44

AC/A = 6 + (16-6)/3

AC/A = 9.3 (high)

Front 45

What is generally considered as a "normal" AC/A ratio (when using heterophoria method)?

Back 45

1/2 IPD

Front 46

What differentiates the heterophoria method and gradient method of measuring AC/A ratio?

Back 46

Heterophoria method - varies fixation distance
Gradient method - varies lenses to change stimulus to accommodate

Front 47

How does one use the gradient method to compute AC/A ratio?

Back 47

- plus lenses at near (+3.00's)
- minus lenses at distance

Front 48

(T/F) the most accurate method of measuring AC/A ratio is the heterophoria method.

Back 48

False - Gradient method is more accurate

Front 49

What is generally considered a normal AC/A ratio (when using gradient method)?

Back 49

AC/A ratio between 3 and 5

Front 50

Use the gradient method to compute AC/A ratio:

Original dev: XT 2 p.d.
Minus lens -2 D
Dev with minus lens: ET 8

Back 50

AC/A ratio = (8 + 2)/2 = 5

normal