Clinical: Smooth Vergences Flashcards
Bifoveal fixation is
retinal images aligned and on the fovea of both eyes
when a patient does not have corresponding retinal points they may experience
double vision
What stimulates motor fusion for vergences
retinal disparity
Motor fusion allows binocular vision and sensory fusion which creates
stereopsis
Abnormal retinal disparity can occur due to:
- New onset eye turn
- prism induced in front of one eye
Diplopia stimulates
vergence eye movements
Vergence eye movements help re-establish _____, _____, and _____
fusion, binocularity, and stereopsis
Versions are
conjugate eye movements
examples of versions
saccades and pursuits
Versions use ____ muscles
yoked
vergences are
disconjugate eye movements
What are three types of disconjugate eye movements
convergence, divergence, and vertical
Four types of vergences:
Tonic convergence
fusional vergence
accommodative vergence
proximal convergence
tonic convergence is
the difference between anatomic and physiologic positions of rest
The anatomical position of rest for the eyes is described as
where the eyes would sit if there were no innervation for the EOMs and is based on anatomy of EOMs origins and shapes of orbit
In anatomical position, the eyes would sit
in divergent position
The physiological position of rest for the eyes is described as
constant, baseline innervational tine to the EOMs when awake/alert
In physiological position, the eyes would sit
more convergent than anatomical position
Tonic convergence determines the amount of _____ ____
distance phoria
excess tonic convergence =
esophoria
deficiency in tonic convergence =
exophoria
Fusion vergence maintains
single, binocular vision
fusion vergence compensates for
excess or deficient tonic convergence (a phoria)
Fusion vergence prevents a phoria from becoming a
tropia
fusion vergence is autonomic but can be
voluntary
example: you can cross your eye
Positive fusional vergence(PFV) is
Eyes converge
Which patients use PFVs to maintain single vision? (eso or exo)
exophoria patients
Negative fusional vergence (NFV) is
eyes diverge
Which patients use NFVs to maintain single vision?
esophoria patients
Vertical Fusional vergence (VFV) is
eyes moving up or down
What do hypophoria pts use to maintain single vision?
supra vergence
what do hyperphoria pts use to maintain single vision?
infra vergence
Supravergnce moves eyes
UP
Infravergence moves eyes
DOWN
Accommodative vergence is
a change in convergence that occurs with a change in accommodation
excess plus lenses relax accommodation and cause the eyes to
diverge
excess minus lenses stimulate accommodation causing the eyes to
converge
Increasing the testing distance relaxes accommodation causing the eyes to
diverge
Decreasing testing distance stimulates accommodation causing the eyes to
converge
Negative Relative Accommodation(NRA) tests
relaxation of accommodation
NRA indirectly tests
PFVs
During the NRA test, you increase plus lenses so the the pt has to use
PFVs to keep the target single and clear
Positive Relative Accommodation(PRA) tests
relaxation of accommodation
PRA indirectly tests the
NFVs
During PRA, you increase minus lenses causing the pt to use
NFVs to keep the target clear and single
What vergence is used to calculate AC/A ratios
accommodative convergence
What is proximal convergence?
convergence due to awareness of a near target
What are the two methods of testing vergences:
1.smooth vergences
2.step vergences
During smooth vergences the pt will look at a single letter as the examiner increases the amount of prism forcing the eyes to
move the target to maintain single vision
During smooth vergences the target will move toward the
apex of the prism
During smooth vergences, as the target moves toward the apex of the prism it stimulates
retinal disparity so the eye must make vergence movment to keep binocularity
An object on the left visual field stimulates the temporal or nasal retina for OD and OS
OD: temporal retina
OS: nasal retina
During vergence testing, the prisms moves the image towards
its apex in the pts visual field
The image from the prism will project
to the retina of opposite visual field
The eye will turn in the direction fo the image in the visual field to
align fovea with retinal image and maintain binocular fusion
A BI prism over the left eye moves the image
out of the left visual field
A BI prism over the left eye will move the target to project
to the left nasal retina
A BI prism over the left eye causes the eye to move ____ to maintain foveal fixation
out
Two types of lateral smooth vergence testing:
distance lateral vergences
near lateral vergences
What do you instruct the pt for distance or near lateral vergences?
inform me when the target becomes blurred and/or when the target becomes double
For distance and near lateral vergences you always test BI or BO first. Which one and why?
BI because BO affects accommodation and convergence that it may alter the BI results
Purpose of distance lateral vergence test
test the patient’s ability to use horizontal vergence to maintain binocular vision
target for distance lateral vergence test
single letter, 2 lines larger than BCVA in the worse seeing eye
“0” for DLV is placed at
12 o’clock for both eyes
should you stop and write down each number the patient says blur or double at as you go through the test?
no just remember it and say it out loud idiot
To record DLV, you add
the prism from both eyes together as their total prism
for blur, break, recovery
The recovery prism should always be ___ than break
less
For base out vergences, when the image blurs, you’ve reached the pts ____ ___.
PFV limit OR accommodative limit?
For base out vergences, as you reach blur and keep going the pt is now using their
accommodative convergence- sacrificing clarity to avoid double vision
For base out vergences, when the image breaks the pt has reached their limit for ____ ___ AND ___ ____
fusional vergence and accommodative convergence
For base out vergences, when the image recovers it is back within the limit of the pts ___.
PFV
For base out vergences, If there is no blur reported then
the break is the limit of the pt’s PFV
For base in vergences, when the image blurs, you’ve reached the pts ____ ___.
NFV limit OR accommodative limit?
For base in vergences, as you reach blur and keep going the pt is now
relaxing their accommodative convergence to diverge their eyes
For base in vergences, when the image breaks the pt has reached their limit for ____ ___ AND ___ ____
fusional vergence and accommodative convergence
For base in vergences, when the image recovers it is back within the limit of the pts…
NFV to allow fusion
For base in vergences, If there is no blur reported then
the break is the limit of the pt’s NFV
When testing BI vergences at a distance there should be no ____ ___. Why?
blur point because your pt shouldn’t be using accommodation at distance so there is nothing to relax
Near lateral vergences illumination
full overhead with stand lamp
Near lateral vergences has the near card at
40cm
target for near lateral vergences
a vertical line of letters
Two types of smooth vertical vergences testing
distance vertical vergences and near vertical vergences
You use vertical vergences when the pt has
hyperopia
should you have a blur point for vertical vergences
No, because accommodation is not used in vertical alignment
BU measures
infravergence
BD measures
supravergence
Purpose of distance vertical vergence test
test the patient’s ability to use vertical vergence to maintain binocular vision
Target for distance vertical vergence test
single letter, 2 lines larger than BVCA in the worse-seeing eye
For DVV test, you place the “0” at
horizontal for both eyes
For vertical vergence test, you only move
the prism over ONE eyes, not both
For recording vertical vergences make sure to include
distance or near
which eye was tested
If you go past zero for recovery, you record it as
a negative number
vertical phorias are defined by the
hyper eye
For DVV, when the image breaks, you have reached the pt’s limit for
supra/infra vergence
For DVV, when the image recovers you are back within the
patients’ vertical vergence and they are able to regain fusion
illumination for near vertical vergence
full overhead with stand lamp
target for NVV
horizontal line of letters, near card at 40cm
Vergence testing with BI/BO measures
reserves or magnitude of fusional vergences
pts with large, long-standing phorias may have
large compensating vergences
Pts with large compensating vergences have binocular systems that have
adapted which keeps them asymptomatic
if a patient with a longstanding 15 exophoria has a large amount of PFV, their
BO blur value will be high
If there is not enough compensating vergence, it will not be sufficient to compensate for a phoria and it will lead to
a patient being symptomatic
