BV 4 - deviation variables

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  1. What are the 9 deviation variables?
    • 1. Direction
    • 2. Frequency
    • 3. Magnitude
    • 4. Laterality
    • 5. Dominance
    • 6. ACA
    • 7. Cosmesis
    • 8. Variability
    • 9. Comitance
  2. Frequency?
    • constant
    • intermittent % at dx and near
    • observe before disassociation
  3. Magnitude?
    • angle of deviation at primary angle
    • far and near
    • control accom- full rx, use accom target
  4. Laterality?
  5. Dominance?
    maybe one eye used for dx and one for near?
  6. ACA
    • determines if strab has accom component
    • accomm may decrease deviation
    • may determine what rx to give
  7. Factors favourable for ST and unfavourable for XT?
    • +ve Lambda angle
    • narrow nose bridge
    • absence of epicanthus
    • large PD
    • narrow face
  8. Factors favourable for XT and unfavourable for ST?
    • -ve angle lamba
    • wide nose bridge
    • wide face
    • presence of epicanthus
    • small PD
  9. Factors that suggest non-comitance
    • abnormal head position - usually towards affect muscle
    • version underaction - test duction
    • alternating CT in diff DAF
  10. How to differentiate if there is a mechanical obstruction or not?
    • version testing - issue
    • duction testing:
    • a) no issue - not mechanical
    • b) issue - mechanical
  11. When do you use a Park's 3 step test and what is a disadv?
    • When a vert deviation is noted
    • only works if one muscle is affected
  12. L hyper in primary gaze, hyper worse in R gaze, hyper worse with L head tilt. What muscle is affected?
  13. What is an alternating CT in 9 DAF and what to watch out for?
    • test for incomitance and magnitude
    • watch out for prismatic effect of specs
  14. What is a Hess Lancaster chart?
    • confirms diagnosis of paretic muscle
    • can confirm if more than one muscle affected
    • quantifies deviation
  15. What tests are available determine if there is a deviation?
    • listening to parents
    • direct observation
    • hirschberg
    • krimsky
    • bruckner
    • 4BO prism test
    • uni and alt CT
  16. What is angle lambda?
    angle between the pupillary axis and line of sight
  17. What is a positive angle lambda?
    nasal corneal reflection
  18. Hirschberg test?
    • comparing corneal reflection when shining a torch infront of px 33-100cm away
    • symmetrical and equal = no/small deviation
    • 1mm displacement = 22PD
  19. Hirschberg: OD +0.5mm OS -1mm
    • 0.5mm nasal deviation in OS
    • 11PD LST
  20. What is the Krimsky test?
    similar to hirschbirg but placing prism infront of the nondeviating eye to reposition corneal reflex of deviating eye to same relative position as nondeviating eye
  21. Adv of krimsky?
    can perform on blind or deep amb
  22. What are the disad of CT?
    • cant use on blind/deep amb- suppression
    • contaminated by EF
    • will not usually reveal a microtropia
  23. Why can you not use unilateral to measure magnitude?
    • you will not measure full amount of deviation
    • they may be using fusional conv/diverg
  24. XT, diverg excess and CT?
    • do test in a hall way/6m room
    • usually problems in the far dx
  25. What is a primary angle?
    • the amount of deviation when the non-paretic eye is fixating
    • the prism will be placed over the paretic eye
  26. What is the secondary angle?
    the amount of deviation when the paretic eye is fixating
  27. When might there be a difference between the primary and secondary angle?
    When incomitance is present, the secondary angle will be larger than the primary angle. This occurs when the good eye is occluded and the deviating eye is forced to pick up fixation - alot more innervation is required and hence the yoked muscle in the good eyes is deviated much more.
  28. What is the minimum difference between the primary and secondary angle to consider the prescence of incomitance?
    >9PD or 5deg
  29. What is the phi test?
    • subjective alternating CT
    • keep adding prism until px responds that image doesnt move
  30. How and why and when is a 4BO test used?
    • to detect microtropias
    • use if decreased VA in one eye and no movement on CT
  31. What would you see in 4BO test in a normal BV px?
    • 1. prism over OD: OU both version away from base
    • 2. OS vergence movement towards base
    • 3. Same if prism over OS
  32. What would you see with a microtropia (ST) in 4BO test (say OD is normal)?
    • 1. Prism over OD: OU version away from base
    • 2. No vergence of OS

    1. Prism over OS: No movement
  33. Bruckner test?
    • useful for microstrab
    • fundus reflex
    • brighter eye = deviating eye
Card Set:
BV 4 - deviation variables
2014-12-02 06:57:14

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