PC - Binocular Vision 2 Vergence - Week 2 Flashcards
(31 cards)
What is the vergence of an eye when it has no EOM innervation?
17 beyond parallel
What is the tonic vergence of an eye?
Parallel or slightly esophoric
What is the vergence of an eye in the absence of stimuli (no light)?
physiological position of rest.
Name 5 tests to measure vergence.
Prentice card Maddox rod Von graefe Cover test Maddox wing
True or false
Von graefe is the ideal test for children
False
Define vergence facility, and how its measured.
Speed and accuracy of the vergence system to uptake a convergence or divergence response on demand.
Measured using prism flippers, similar to accommodative facility
Name 3 anatomical factors that influence the vergence system.
Size
Shape of the globe
Position of EOM insertion
Name 3 neurological factors that influence the vergence system.
Any lesions affecting innervation of cranial nerve III, IV, and VI.
Name 5 general factors that influence the vergence system.
Fatigue Alcohol Tobacco Medications Prisms in glasses
Name the 6 types of vergence responses.
Fusional Proximal awareness Accommodative Tonic Voluntary (convergence) Vergence adaptation
Describe tonic vergence.
Eyes are 17^ beyond parallel when all innervation to EOMs are cut.
Tonic vergence brings EOMs back to parallel or slightly esophoric.
What can be said of tonic vergence?
It is the physiological position of rest (in the dark as well).
Define vergence posture, and describe 5 means of measuring it.
Vergence posture is heterophoria, measured by: Prentice card Von Graefe Maddox rod Cover test Maddox wing (antiquated)
Name the test to measure vergence range/amplitude.
Positive and negative relative convergence
Name the test to measure vergence facility.
BI and BO flipper challenge
Define vergence posture.
How accurately the eyes point relative to the visual stimulus location
What is the preferred means of measuring vergence posture (heterophoria) in school-age children?
Prentice card
Which is more repeatable, maddox rod or Von Graefe?
Maddox rod
True or false
Von Grafe is the preferred method of measuring phoria in children.
False
What is one advantage of maddox wing above all other tests?
It can detect cyclophoria, and is sometimes used when it is suspected.
What is the main disadvantage of the maddox wing?
Inability to control accommodation.
Define vergence amplitude/range.
The capacity of the vergence system, and how much it can converge/diverge on demand.
Describe how PRC and NRC are carried out (2).
Use the prentice card and the diamond for fixation. Use the prism bars, and add more ^D, measuring blur, break, and recovery.
Can also be done using the phoropter head, set to converging, and more prisms added using the risley prism.
Are the PRC/NRC tests objective or subjective?
Subjective, requiring patient input.
