Week 6 Flashcards
What are the 4 types of vergence found in maddox’s hierarchy?
- Tonic
- Proximal
- Accommodative
- Fusional
What type of vergence is not apart of maddox’s hierarchy?
Voluntary vergence
One’s anatomical eye position is found in what state?
Found in death, anesthesia, deprived environments
Explain what tonic vergence does.
Brings eyes from divergent anatomical position or rest to convergent physiological position of rest
Physiological position is found in what type of individuals?
Alert individuals in the absence of stimulus
Balance of innervation to the EOMs puts the eyes in a neutral state. WIT?
Tonic vergence
How do we determine tonic vergence?
Estimated by distance phoria on cover test
Tonic vergence can be revealed when stimulation is under what conditions?
- Reduced illumination
- Eccentric stimulation
- Physiological stress: Intoxication
What is the most important componenet of vergence? What is it induced by?
Fusional Vergence
- induced by binocular disparity
Fixation disparity is termed __? How is it measured?
An inaccuracy in vergence
Measured in minutes of arc (1’ = .029PD)
What is the most common type of fixation disparity?
exo FD
When the demand on vergence is large, the size of FD _____.
increases
BI prism increases what type of FD?
Eso FD
FD is used by what type of vergence system to improved vergence accuracy?
Closed-loop vergence system
FD reveals vergence inaccuracy during ____ ____ while the eyes look at the same target
binocular fixation
Binocular fixation of the same target is comprised of what vergence types for near?
- Tonic
- Proximal
- Accommodative
What are the methods to measure phoria?
- CT
- von Graffe
- Maddox rod
What is associated phoria?
the amount of prism it takes to neutralize one’s fixation disparity
What is dissociated phoria?
The amount of prism it takes to neutralize one’s phoria (in CT)
What is the average FD in a normal patient?
~ less than 5mins of arc (0.145pd)
With increasing prism load, the magnitude of FD ___
increases
BO prisms cause what type of FD?
cause Exo FD(eyes converge)
Describe a Type 1 curve?
Equally susceptible to BI and BO prism loads
Describe Type II curve?
Manage BO prism better than BI
Describe Type III curve.
Manage BI prism better than BO
Describe Type IV curve.
Can’t manage any prism
Prism adaptation acts to what?
reduce the stress in the vergence system
Lenses can be used to affect FD by inducing what?
Accommodative vergence
Prisms are used to affect FD by inducing what?
Disparity (fusional) vergence
Minus lenses induce accommodation + increases accommodative vergence to result in what type of FD?
Eso-FD
- causes eyes to diverge
Plus lenses relax accommodation + decreases accommodative vergence resulting in what type of FD?
Exo - FD
Symptomatic patients with an eso-FD can benefit from what type of lenses?
Plus lenses
VT works better with eso or exo?
Exo
- easier to train convergence than divergence
