Assessing the Deviation Flashcards
3 categories of Ocular Deviation or misalignment?
- Heterophoria
- Heterotropia
- Fixation Disparity
Eye movement must be ___________ to be a phoria
latent
Is heterophoria measured under associated or dissociated conditions?
dissociated
Von Graefe, Prism and alternate cover test, Maddox rod and modified thorington card are all techniques to measure what type of misalignment?
Heterophoria
Is Heterotropia manifest or latent?
manifest
Is heterotropia measured under associated or disocciated conditions?
associated
What are the techniques used to measure heterotropia?
Unilateral cover test, simultaneous prism cover test, Hirschberg
What do we call a small misalignment that occurs even while fusion is present?
fixation disparity
Is fixation disparity measured under associated or disociated conditions?
associated
Unit: minutes of arc
Disparometer, Saladin or Wesson cards and the Bernell Box are used to measure which type of ocular misalignment?
Fixation disparity
prismatic effects of high Rx
Does high plus increase or decrease the devation?
decrease
BO induced for ET; BI induced for XT
High minus will increase the devation
What is the typical value for Angle Kappa?
Angle Kappa: anatomical; angle between pupillary and visual axis
+0.50 mm
(+)= nasal
Hirschberg is performed monocular/binocular while Kappa is performed monocular/binocular
binocular, monocular
We compare the measurements from both, if there is a difference, then strabismus is suggested
When do we use Hirschberg/Kappa to determine the presence of strabismus?
Very young patients or patients with very poor monocular VA
What are the corneal reflex locations for the following deviations?
1. Esotropes
2. Exotropes
3. Hypertrope
4. Hypotrope
- Temporal
- Nasal
- Inferior
- Superior
What type of deviations are the following atypical head positions associated with?
1. Tilt
2. Tip
3. Turn
- possible cyclo/ vertical
- possible A/V pattern
- Possible horizontal muscle/ nerve, null point
Do the following factors magnify ET or XT?
* negative angle kappa
* wide nose bridge
* prominent epicanthal folds
* small PD
* Wide Face
ET
XT is magnified by opposite factors: large PD; absence of epicanthal folds; narrow nose bridge and positive angle kappa
what important quality about a deviation is NOT identified by performing PACT?
laterality
can ONLY report amount and direction of prism used to neutralize
When is a vertical deviation considered primary?
When it is present with horizontal neutralization
Secondary: vertical no longer present after horizontal neutralization
During Simultaneous Prism Cover Test, which eye gets the prism and which gets the occluder placed in front of it?
deviated eye: prism; non-deviated eye: occluder
What type of deviation MUST be present to perform simultaneous prism cover test?
manifest- either constant or high frequency intermittent (90+%)
Why can’t we stack prisms in the same plane?
Resultant power is stronger than simple addition
CAN stack in opposite planes (ie BI with BD)
Which test determines small angle strabismus?
4 BO prism test
How is the magnitude of cyclo determined when performing double Maddox Rod?
rotate Maddox rod lenses until lines are parallel, then read straight off of trial frame (if rotated 5 degrees outward, then 5 degrees excyclo)
