FD

when should we not prescribe prism w associated phorias

CHECK for prism adaptation apply prism for 15 mins then reassess if FD returns or if AP is larger, pt has adapted - don't rx

necessary components of fd testing

a portion only seen by OD and a portion only seen by OS a binocularly seen fusion lock

why can fixation disparity be useful to rx vertical prism

bc there is no accommodation involved - vergence adaptation is much slower and easier to measure

crossed FD stimulates uncrossed FD stimulates

convergence divergence - uncrossed

borish card how to read FD

each line is 10' add together both sides to find total

why can FD be too large

either FV is weak and needs more stimulation or FV is overloaded by other vergence innervation failures (weak accommodative vergence) more common

type 2 FD curve

eso resistant to VT

type 3 FD curve

exo somewhat resistant to VT

explain for associated phorias - percieved deviation is opposite of turn of eye

if top line moved left, the right eye viewing that line turned right - exo

without prism adaptation, the FD curve would look

linear

associated phorias tend to be ________ for exos and _______ for esos

lower for exos higher for esos

dissociated phorias tests

measurement when eyes are disociated CT, VG, maddox rod

type 1 FD curve

most pts normal very trainable higher slope - more symptoms

associated phorias are used mostly for

prescribing vertical prism

which prism to neutralize associated phorias

same as CT exo - BI eso BO opposite or minus exo plus eso

what you NEEd for fixation disparity testing

single binocular vision..... bitch no strab no amblyopia

how to rx based off fixation disparity curves

smallest amt of prism in the flat area if no flat area, rx the x intercept aka associated phoria

t/f FD can either be too large or too inappropriate

t

associated phorias which tests

the minimum amt of prism needed to eliminate FD while eyes are fused ex: wesson card, saladin card, mallet unit

t/f associated phoria is the amt of prism (pd) to correct fixation disparity (min of arc)

truw

type 4 FD curve

unstable binocularity usually after strab surgery poor fusional vergence

y intercept x intercept slope at y axis

y = habitual FD x = associate phoria slope = u want this to be flat, no symptoms