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OPTM5103/5104 > Binocular Vision > Flashcards

Binocular Vision Flashcards

1
Q

What does Amplitude of Accomodation measure?

A

Measures TOTAL accomodation response capacity

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2
Q

How do you measure Amplitude of Accommodation?

A
  1. Conduct test with full distance prescription, monocularly and in full illuminated conditions
  2. Distance: Start at about 30-40 cm
  3. Target: Use an accommodative target close to patient resolution capacty
  4. Move the target towards the patient until the patient reports ‘the first sustained blur’
  5. Measure the distance between the target adn the corneal plane
  6. Repeat twice more and take average
  7. Convert distance to dioptres D = 1/d(m)

*Record Amp Acc (D) = inverse of NPA in metres

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3
Q

What is expected values for Amplitude of Accommodation?

A

–> Expected value (Hofstetter’s equation) = 18-0.3(age)

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4
Q

What does MEM retinoscopy measure?

A

It investigates accuracy of the accommodative response

It is an objective test

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5
Q

What conditions do you MEM retinoscopy under?

A
  1. Illumination: dim illumination - but enough to read the MEM card
  2. Binocular: test is performed binocularly but optom. assess monocular response for each eye
  3. Px wears full distance prescription
  4. Ensure patient is actively reading the target
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6
Q

How to perform MEM retinoscopy?

A
  1. Examiner is positioned so that near card and retinoscopy is 40cm away from patient
  2. Ask patient “Read the word on the card out loud”
  3. With the retinoscopy, sweep streak across the horizontal and vertical meridians of one eye
  4. Evaluate the reflex
    –> If with motion, BRIEFLY insert a plus lens (+0.50 D)
    –> If against motion, BRIEFLY insert a minus lens (-0.25 D)
  5. Increase in 0.25 D steps, re-evaluated the retinoscope reflex each time until a neutral reflex is observed and record the amount of plus or minus added to achieve neutrality.
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7
Q

What do the results of a MEM mean?

A
  • Normal range = +0.25 D to +0.75 D
  • Lag of accommodation = more than this amount (> +0.75D)
  • Lead of accomodation = minus (< +0.25)

PLUS = lag
MINUS = lead

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8
Q

If a patient has a lag, what does this indicate?

A
  • Patient has accommodative insufficiency
  • Presbyopia or pre-presbyopia
  • Uncorrected or under corrected hyperopia
  • Over minused patient
  • Esophoria with insufficient vergence (patient under accomodates to keep fusion)
  • Patient wasn’t paying attention
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9
Q

If a patient has a lead of accommodation, what does this indicate?

A
  • Accommodative spasm (‘pseudo-myopia)
  • Exophoria with insufficient compensating vergence (patient over-accomodates to keep fusion)
  • uncorrected or under corrected myopia
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10
Q

What does Accommodative Facility measure?

A

Measures the flexibility of the accommodative system to engage and relax in response to demand binocularly

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11
Q

How do you conduct Accommodative Facility test?

A
  1. Place the plus lenses infront of the patients eyes, and ask them to make the near target clear
  2. Once htey are able to maintain a clear image, flip the flipper to minus lens side
  3. Each cycle is clearing both the plus and minus lenses
  4. Count number of cycles in one minute
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12
Q

What conditions do you perform the Accomodative Facility test under?

A
  • Distance position: 40 cm
  • Wearing any distance correction
  • Target: use an accommodative target two lines larger than their best Near VA
    –> Near vision chart on Prentice card
    –> Fixation stick
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13
Q

How do you record the results of an Accomodative Facility test?

A
  • Note the amount of cycles a patient is able to complete in one minute
  • E.g. 11 CPM @ 40cm +/-2.00DS
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14
Q

What are normative ranges for Accomodative Facility?

A
  • Children = 5-7 cpm
  • Adults = 11 cpm +/- 5
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15
Q

What does PRA (positive relative accommodation) measure?

A
  • Measures the maximum ability to stimulate accommodation while maintain clear, single binocular vision
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16
Q

What does NRA (negative relative accommodation) measure?

A
  • Measures the maximum ability to relax accommodation while maintaing clear, single binocular vision
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17
Q

How do you perform PRA/NRA test?

A
  1. Set up the patient behind the phoropter
  2. Position the near letter chart at 40 cm
  3. Use an accommodative target two lines larger than their best near VA
  4. Introduce +/- 0.25 DS binocularly until sustained blur for both plus and minus lenses
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18
Q

Which lens do you offer to test for PRA?

A

Minus –> minus lens stimulates accommodation

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19
Q

Which lens do you offer to test for NRA?

A

Positive –> positive lens relaxes accommodation

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20
Q

What are expected PRA/NRA values?

A

–> NRA = +2.00 DS, +/- 0.50 DS
–> PRA = -2.50 DS , but a young person should be > -3.50 DS

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21
Q

What does the Pretience card (Howell-Dwyer) measure?

A
  • Assessment of dissociated state of eyes in free space
  • Measures horizontal vergence posture (posture = resting state)
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22
Q

How to conduct the Howell-Dwyer (Prentice card) test?

A
  1. Conduct test under full illumination
  2. Perform at 3m (distance) and 33 cm (near)
  3. Place a 6PD base DOWN lens in front of the RIGHT EYE to generate diplopia
  4. Ask the patient which number and colour is the top arrow pointing to
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23
Q

What does it mean, if the arrow points to the blue side on the phoria card?

A

Blue = exphoria

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24
Q

What does it mean, if the arrow points to the yellow side on the phoria card?

A

Esophoria

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25
Q

What are the normative ranges for Prentice card test?

A

Near: 3 exo +/- 3 △
Distance: 1 exo +/- 2 △

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26
Q

What does the Maddox Rod test measure?

A
  • Measures vertical posture (phoria)
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27
Q

How to conduct the Maddox Rod test?

A
  1. Under dim illumination
  2. Perform with either the phoropter or with trial frame
  3. Performed at distance (6 m) or near (33 cm)
  4. Place Maddox rod in fron of RE with grooves vertical
  5. Provide a bright spotlight distance target (use a pentorch for near target)
  6. Ask the patient if the red horizontal line is above or below the light
28
Q

How to interpret the results of Maddox Rod test?

A
  • If the red horizontal line is ABOVE the light = Right Hypophoria
  • If the red horizontal line is BELOW the light = Right Hyperphoria
  • If line passes through the light = no vertical misalignment
29
Q

What does the Von Graefe test measure?

A
  • It is an assessment of dissociated state of eyes in instrument space
  • It can measure both vertical and horizontal vergence posture
30
Q

Under what conditions should you perform the vergence test under?

A
  • Full illumination
  • Vertical and Horizontal phoria
  • Distance and near assessment
31
Q

How do you conduct the horizontal Von Graefe test?

A
  1. Place 6BD in front of RE using Risley prisms (dissociating)
  2. Place 12 BI in front of the LE using Risley prism (measuring)
  3. Display vertical line of letters on the letter chart (2 lines above patients VA)
  4. Verify the patient can see two images one above and below
  5. Instruct the patient you are moving the lower image and the advise when it is directly underneath the top - like buttons on a shirt
  6. Increase/Decrease the horizontal prism until 2 images line up
32
Q

How do you conduct the vertical Von Graefe test?

A
  1. Place a 6 BD in front of RE (measuring)
  2. Place a 12 BI in front of the LE (dissociating)
  3. Put horizontal line of letters on the chart
  4. Verify the patietn can see two images one above and below
  5. Instruct the patient you are moving the images and to instruct when the images lime up like headlights on a car
  6. Increase/Decrease the vertical prism until 2 images line up
33
Q

What does Near Point of Convergence measure?

A
  • Measures the TOTAL convergence response capacity
  • Free space test, measuring AMPLITUDE
  • Subjective: patient report diplopia
  • Objective: examiner observes break to eye turn
34
Q

Under what conditions should you perform the Near Point of Convergence under?

A
  • Full illumination
  • Binocular testing conditions using near correction
  • Accomodative target for young patients (pen tip if presbyopic)
35
Q

How do you conduct the Near Point of Convergence test?

A
  1. Examiner is positioned in front of patient to watch eye movement
  2. Instruct patient to look at the accommodative target
  3. Starting ~40cm away, bring the target closer to patient’s nose
  4. Ask the patient to report when they report diplopia and record this value or if the practitioner observes a break in convergence
  5. Pull the target back and ask the patient to report when they see one target clearly
  6. Record results over an average of three attemps assessing for fatigue
36
Q

What are normal ranges for Near Point of Convergence?

A
  • 5 cm +/= 2.5 cm
  • Recovery value = 7cm
37
Q

What does PRC/NRC with prism bar measure?

A
  • Measures convergenc and divergence fusional reserves/range
38
Q

How do you perform PRC/NRC with prism bar?

A
  1. Either using prism bar (free space) or phoropter (instrument space)
  2. Working distance of 6m, with distance correction and focusing on a fixation target slight larger then BCVA
  3. To test for horizontal fusional results use a verticle line target
    To test for vertical fusion reserves use a horiztonal line target
  4. To measure near (33cm) use Prentice car (also wearing near correction)
  5. Instruct the patient to keep the target clear and single and report when image is blurred/double vision occurs
39
Q

How to record reuslts from PRC/NRC with prism bar?

A
  • Blur/Break/Recover
    –> Blur = when patient first report blur - can they get it clear?
    –> Break = when diplopia occurs - can they get it one?
    –> Recovery = Reducing the prism until the image is single again
  • Record example:
    –> PRC = 18/25/15
    –> NRC = X/20/11
40
Q

When measuring PRC with prism bar, how should you position the prism lens over the eye?

A

PRC = base OUT (makes the eyes converge)

41
Q

When measuring NRC with prism bar, how should you position the prism lens over the eye?

A

NRC = base IN (makes the eyes diverge)

42
Q

What results would you expect for someone with accommdative insufficiency?

A
  • Lag on MEM
  • Difficult clearing minus
  • Low NPA
  • Slow facility
43
Q

What results would you expect for someone with accommodative excess?

A
  • Abnormal or variable lead on MEM
  • Distance blur (pseudo-myopia)
  • Fails plus on facility
44
Q

What results would you expect for someone with convergence insufficiency?

A
  • N Exo > D Exo
  • Reduced PRC
  • Low NPC
45
Q

What results would you expect for someone with convergence excess?

A
  • N Eso > D Eso
46
Q

What results would you expect for someone with divergence excess?

A
  • D Exo > N Exo
47
Q

What results would you expect for someone with divergence insufficiency?

A
  • D Eso > N Eso
  • D blur/diplopia
48
Q

What test measures accomodative amplitude?

A

NPA - Near Point of Accommodation

49
Q

What test measures accomodative posture?

A

MEM Near retinoscopy

50
Q

What test measures accomodative reserves/range?

A

PRA/NRA - Positive and Negative Relative Accommodation

51
Q

What test measures accomodative facility?

A

+/- Lens flippers

52
Q

What test measures vergence amplitude?

A

NPC - Near Point of Convergence

53
Q

What test measures vergence posture?

A

Phoria measurement (prentice card, Von Graeffe, Maddox rod)

54
Q

What test measures vergence reserves/range?

A

PRC/NRC - Positive and Negative Relative Convergence

55
Q

What test measures vergence facility?

A

Base IN/OUT prism flippers

56
Q

What are indications for conducting ocular motility?

A
  • Baseline measurement
  • Headsaches or asthenopia during near tasks
  • Diplopia
    –> Systemic
    –> Vascular
    –> Tumour
    –> Head trauma
    –> Inflammation
    –> Infection
    –> Toxicity
57
Q

How do you perform ocular motility test?

A
  1. Ask the patient to follow the fixation target with both eyes
  2. They must keep their head still
  3. Ask the patient if they experience nay pain or double vision in any direction
  4. Observe for any restriciton or limitation
58
Q

What does the cover test measure?

A
  • Cover test, assess ocular alignment at near and distance
59
Q

How do you perform an alternating cover test?

A
  1. Ask the patient to focus on an appropriate target (near letter on fixation rule or letter on VA chart)
  2. The cover is moved from one eye to the other (hold for 2-3 seconds over each eye then move rapidly to the other eye to prevent refixation in-between)
  3. If either eye moves after the cover is taken off, then a phoria (at least) is present
60
Q

How do you perform a cover/uncover (unilateral) test)?

A
  1. Ask the patient to focus on an appropriate target (near letter on fixation rule or letter on VA chart)
  2. One eye is covered; the optomerist observes the other eye for movement
  3. The covered eye is then uncovered
  4. If the eye that had been covered, moves to focus on the target (while the other eye moves away), strabimus is present
  5. Repeat for the other eye
61
Q

Under what conditions should you perform a Random dot Stereo Acuity Test?

A
  • Good lighting
  • Polarised glasses
  • Near correction, if needed
62
Q

What does the AC/A ratio measure?

A
  • Measures the change in vergence for 1D of change in accommodation
63
Q

What is the expected AC/A ratio?

A

–> 4:1, with a standard deviation of +/- 2

64
Q

How do you measure AC/A ratio?

A
  1. Underfull full illuminaiton and test at 22cm. Optometrist should hold the Phoria card
  2. Patient wears their habitual near correction
  3. Place a 6△ PD in front of the right eye to generate diplopia through dissociation
    –> the patient shoudl see two scales verticlaly displaced
  4. Measure the phoria:
    –> ask the patient to look at the top arrow and identify which number it is pointitng to
    –> ask if the numbers are clear and whether the arrow is moving or stable. If the numbers are blurry encourage them to make it clear, then take measurement
  5. Measure again using +/- 1.00 D and +/- 2.00 D flippers, beginning wiht plus
    –> note the measurement and whether there is any blur or movement
    –> Calculate and record the gradient AC/A ration to plus and minus
65
Q

If this is this the reuslts from doing a AC/A ration test, what would be ther AC/A ratio to minus?

+2: 4 exo
+1: 1 eso
0: 4 eso
-1: 11 eso
-2: 20 eso

A

AC/A ratio to minus:

(20-4)/2 = 8:1

OPTM5103/5104 (4 decks)

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