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OD1 Semester 2 - Integrated Ophthalmic Sciences and Preclinical Optometry > Binocular Vision 1 - Week 2 > Flashcards

Binocular Vision 1 - Week 2 Flashcards

1
Q

By what age is accommodation fully developed?

A

6 months

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2
Q

What are the 4 major factors that stimulate accommodation?

A
  1. Blur - primary driver
  2. Proximal Awareness - drives accommodation based on where the object is in space or where you think it is
  3. Vergence - movements are accompanied by corresponding accommodation change
  4. Tonic Accommodation - baseline neural activity without any stimuli
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3
Q

What visual symptom can be caused by tonic accommodation?

A

Night Myopia

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4
Q

Describe the neurological pathway for blur driven accommodation

A

Blur triggers afferent pathway

  1. Blur signals in LGN into cortical area 17 + parietal/temporal areas
  2. signal transformed to motor Efferent response at EWN
  3. Efferent: innervate cil. muscle to cause accommodation
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5
Q

Describe the Efferent pathway for accommodation

A

via CIII nerve – cil. ganglion – short cil. nerve – innervate cil. muscle – cause accommodation

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6
Q

What mediates the parasympathetic and sympathetic innervation for accommodation? [2]

A

Parasympathetic: acetylcholine mediated
Sympathetic: noradrenaline mediated

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7
Q

Which type of innervation might play a role in assisting the re-establishment of distance focusing after prolonged near work?

A

Sympathetic

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8
Q

Name 6 factors that influence accommodation

A 
Blur
Luminance
Proximity
Chromatic aberration
Convergence
Age
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9
Q

Average amplitude of accommodation at 45 years?

A

About 4 diopters

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10
Q

Expected amplitude of accommodation at 20 years?

A

About 10 diopters (10cm) or more

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11
Q

Name 5 features of accommodation that we can measure clinically

A 
Posture (lag/lead)
Amplitude (NPA)
Accommodative Facility
Relative Accommodation (NRA/PRA)
Convergence Accommodation (AC/A)
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12
Q

Rank the amplitude of accommodation levels for different ametropia

A

Myopes > Emmetropes > Hyperopes

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13
Q

How do glasses affect amplitude of accommodation? Is this change significant?

A

Hyperopes need to accommodate more with their glasses while Myopes need to accommodate less.

This is only significant if the correction is greater than +/- 5D

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14
Q

How does luminance affect amplitude of accommodation?

A

Accommodative response (relative to demand) is reduced in dim light

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15
Q

What type of neurological deficit might result in changed amplitude of accommodation?

A

Third nerve problems

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16
Q

What two tests are used to measure posture of accommodation?

A
  1. MEM retinoscopy (monocular estimate method)

2. Binocular X cyl

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17
Q

What is the advantage of MEM retinoscopy?

A

Is objective and is undertaken in free space (no phoropter needed)

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18
Q

What does it mean when a px has a ‘lag’ of accommodation?

A

It means they focus just behind the near task they are performing (i.e. focus just slightly further away)

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19
Q

Which is more common: accommodative lag or accommodative lead?

A

Lag. Most people have lag.

They should get better gaming computers then

20
Q

In MEM retinoscopy, why must you scan both eyes first with the retinoscope?

A

Because the accommodative posture in the 2nd eye can change while doing ret on the 1st. You want to know what it was originally also

21
Q

In MEM retinoscopy, what movements represent a lag or lead in accommodation?

A

With movement = LAG
Against movement = LEAD

  • way to remember: so just like with regular ret, the most common condition is the one with the ‘with’ movement *
22
Q

In MEM retinoscopy, for how long should you place the trial lens in front of the spectacle plane?

A

For 1 second each time

also, it’s good to have the lenses on standby so you don’t faff about

23
Q

What is the expected value for MEM retinoscopy?

A

+0.50DS +/- 0.25DS

24
Q

Is Binocular Cross-Cyl objective or subjective?

A

Subjective

25
Q

List disadvantages of binocular cross-cyl

A
  • is NOT in free space and requires a phoropter head
  • is NOT close enough to a real life near task and therefore may not be a true representation of accommodative response at near (b/c lack of proximal cues)
26
Q

Explain the binocular cross-cyl technique

A

Px is placed behind phoropter with NEAR PD and metal rod is inserted into hole. Chart cross target is attached to rod at 40cm.

Add a +/-0.50 auxillary lens to the eyes, with negative cyl axis oriented vertically

Add +ve lenses binocularly until px reports both horizontal and vertical lines are equal

27
Q

In binocular cross-cyl: What represents a LAG in accommodation, and what represents a LEAD in accommodation

A

LAG: horizontal focal lines appear sharper/clearer (b/c they are closer to the retina)
LEAD: vertical focal lines appear sharper/clearer

28
Q

When doing binocular cross-cyl, why do you add a +/- 0.50D auxillary lens with negative cyl axis oriented vertically?

A

This will add minus to the vertical axis and plus to the horizontal axis. That way, assuming posture is perfect, both focal lines should be equally blurry

(we don’t add just + or - to both because we want to distinguish/separate the axes)

29
Q

Expected value for binocular cross-cyl?

A

+0.50 +/- 0.50DS

30
Q

What tests can you use to measure amplitude of accommodation? Are these tests performed binocularly or monocularly?

A

Near Point of Accommodation (NPA)
Refractor Head Near Point Rule
Minus lens to blur

All these tests are performed monocularly

31
Q

For NPA, what is the expected: average amplitude and minimum amplitude?

A

Average: 18 - 1/3(age)
Minimum: 15 - 1/4(age)

32
Q

Is the ‘reverse push up method’ liable to over-estimate or under-estimate accommodation? Why is this?

A

Over-estimate. Due to the magnification effect caused by bringing the target closer and improving acuity

33
Q

Why might being in front of a phoropter provide different or inaccurate results for amplitude of accommodation?

A

lack of proximal cues. Different to real life near vision

34
Q

Define Positive Relative Accommodation (PRA)

A

The amount of accommodation that can be EXERTED to maintain clear single binocular vision without changing vergence or proximal

35
Q

Define Negative Relative Accommodation (NRA)

A

The amount of accommodation that can be RELAXED to maintain clear single binocular vision without changing vergence or proximal

36
Q

How do you perform PRA and NRA?

A

Do this at distance and near:

  • Start with best corrected VA behind either trial frames or phoropter
  • do NRA: add +ve lenses in +0.25DS steps until first sustained blur (ask px to blink eyes to see if sustained)
  • do PRA starting from value obtained from NRA: add -ve lenses in -0.25DS steps until first sustained blur
37
Q

Expected values for accommodative range? (PRA/NRA)

A

+/-2D at near

-2D at distance

38
Q

What is Accommodative Facility?

A

Is the flexibility and sustainability of accommodation while vergence and proximal stay the same
- i.e. “how quickly and efficiently can accommodation change on demand”

39
Q

What test is used to measure Accommodative Facility?

A

Near accommodative facility/flippers

40
Q

Explain the procedure for measuring Accommadative Facility

A

use flippers

  • target at preferred WD (but 33-40cm)
  • flip lenses continuously for 1 minute
  • first test +/-2D flippers: ask which sign is preferred if both +/- cleared
  • if failed to clear/struggled: repeat with +/-1D flippers

Count the cycles per minute for each set of flippers

41
Q

What is the expected cycles per minute for +/-2D near accommodative flippers?

A

8cpm at near with +/-2D flipper

*If using 1D flipper, record preference for + or -. (do this for 2D flipper as well I think)

42
Q

What factors affect our clinical tests of accommodation?

A 
Age
Ocular conditions
Systemic conditions
Medications
Lighting levels
Tests used
Testing conditions
Patient engagement/cognition
43
Q

Name 5 common accommodative dysfunctions

A 
Insufficiency
Excess
Spasm
Ill-sustained
in-facility
44
Q

What are the clinical characteristics of accommodative:

  • insufficiency
  • excess
A

Insufficiency: High lag, low amplitude, poor facility
Excess: Variable VA, NO lag or lead, fails +ve facility

45
Q

What are the clinical characteristics of accommodative spasm

A

Spasm: Reduced VA, Lead, fails +ve facility

46
Q

What are the clinical characteristics of:

  • ill-sustained accommodation
  • accommodative infacility
A

ill-sustained: High variable lag, slow facility

in-facility: Slow facility for both + and -

OD1 Semester 2 - Integrated Ophthalmic Sciences and Preclinical Optometry (49 decks)

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