BV Flashcards
What 4 things must you have for normal binocular vision?
equal ocular images
bifoveal fixation
motor fusion
sensory fusion
BI prism causes __vergence which is associated with NFV/PFV?
divergence
NFV
BO prism causes __vergence which is associated with NFV/PFV?
convergence
PFV
Non strabismus (phoria) is a type of ocular deviation which is only present if ______ ______ is disrupted; _______ ________ is present under normal seeing conditions
sensory fusion
bifoveal fixation
What are the 5 characteristics of the cover tests? (things to consider/record)
Direction Magnitude Speed of recovery from dissociation Comitancy Zone of functional binocular vision
What 5 things need to be assessed and managed with an ocular devation?
frequency magnitude direction laterality comitancy
If eso increases at near then the AC/A ratio is considered?
above average
if exo increases at near by ~3 prism dioptres then the AC/A is considered?
normal
If exo increases at near by»_space;>3 prism dioptres then the AC/A is considered
below average
The unilateral cover test is the only way to determine whether a deviation is?
manifest
Alternating cover test reveals what sort of devations and allows measurement of what??
latent deviations
magnitude
Measuring a deviation with each eye fixating independently (ie measuring primary and secondary deviation) helps identify what kind of strabismus?
paretic strabismus
primary deviation = non-strabismic eye fixating
There are two subtypes of calculated AC/A which are?
calculated stimulus AC/A
calculated response AC/A
Calculated stimulus AC/A assumes what?
accurate accommodative response to target ie no lag or lead
For calculated response AC/A, what do you need to do?
measure accommodative response as significant lead or lag will alter AC/A ratio
Do a calculated AC/A for someone with distance phoria 5 exoP, near phoria 5 esoP with 60mm PD.
Stimulus to accommodation at distance = 0
Stimulus to accommodation at near = 2.5 (40cm)
Stimulus to convergence at distance = 0 prism D
Stimulus to convergence at near = 15 prism D (60/40 x 10) = 15 prism D
Amount of vergence response:
The demand is 15 prism D but have to overcome 5 exoP in distance and also overconverges 5 prism D at near so = 25 prism D
Therefore AC/A = 25/2.5 = 10/1
Gradient AC/A equation =
(deviation with lens - original deviation) / power of lens
Strabismus definition
a type of ocular deviation in which bifoveal fixation is not present under normal seeing conditions
The magnitude of a strabismus which is 4 degrees is equivalent to how many prism dioptres?
7
What are the three main causes incomitancies?
paresis of EOM (trauma, surgery)
cranial nerve palsy (III, IV, VI)
syndrome (Brown’s Tendon Sheath, Duane’s Retraction)
Thorington technique, Lancaster screen and Hess-Lancaster screen are used to evaluate what?
incomitancies due to EOM paresis by assessing eye position in different gaze directions
The primary action of the medial rectus is
adduction
The tertiary action of inferior and superior rectus are?
adduction
The superior obliques primary action is?
incycloduction