Heterophoria Flashcards
normal binocular vision
- both eyes simultaneously cooperating
- single perception of object
- fusing of images from the 2 eyes
sensory fusion
integration of similar images at the cortex
motor fusion
- motor alignement to sustain binocular vision
- tries to eliminate disparities of 2 images
- tries to FUSE as best as possible to make one image
- NEEDS vergence to produce one image
convergence
tries to maintain binocular vision by ensuring images are on corresponding retinal areas of the eye so there is no disparity
NPC
closest distance where the eyes can converge and maintain binocular vision
cover-uncover
- presence of deviation ( ONLY DETECTS TROPIA)
- lateralitly
- frequency (constant/intermittent)
intermittent tropia
shows when dilated or tired
if there is ANY movement in cover/uncover…
tropia only
alternating cover test
- direction
- magnitude
- distance and near
Why is phoria only present on alternating cover test>
because fusion is broken
heterophoria
tendency of the eyes to deviate when fusion is blocked
-when there is something to focus on, there is no tendency to deviate
visual axes
from the fovea to the point of fixation
symptoms associated with heterophoria if fusional amplitudes are not enough
- convergence insufficiency
- convergence excess
- divergence insufficiency
- divergence excess
measurement of phorias and tropias
at distance and near
maddox rod
used to measure horizontal and vertical phoria
rod dissociates the eye
maddox rod phoria test (in space)
need: penlight, madox rod, prisms
- done cc
- hold penlight 40cm for near
- have pt look at muscle light for distance
- hold maddox rod over OD
horizontal phoria
the grooves on the maddox rod are oriented horiztonally. The pt will see a vertical streak
vertical phoria
the grooves are oriented vertically, giving a horizontal streak
red line through the white light
ortho
red line to the right of the light
eso, uncrossed diplopia
red line to the left of the light
exo, crossed diplopia
red line below the light
right hyper
red line above the light
left hyper
suppression
active deactivation of a retinal image in one eye by the visual cortex
-brain prefers to suppress and provide vision as close to binocular vision as possible
alterante suppression in W4D
can see 3 then 4 dots
include when recording
prims for R hyper
BU over OS
prism for L hyper
use BD over OS
Can maddox rod differentiate phoria from tropia?
no
example of recorded maddox rod
DLP with red cc 4 XP, DVP ortho
NLP with red sc 5 XP, NVP 4 R hyperphoria
expected findings in maddox rod
1 prism D to +/- 2 prism D at D
3 prism D +/- 3 prism D at N
modified thorington phoria
uses thorington cards
- D at 10ft
- 40cm at near
instructions for thorington phoria
- same as maddox rod
- cc
- hold maddox rod over OD
- ask where line is relative to the light
- DLP by modified thorington: 4 prism D, DVP ortho
normal findings with thorington phoria
D: 1 pD XP +/- 2 pD
N: 3pD XP +/- 3 pD
3 possible reflexes in Hirschberg
- center of pupil
- nasal to the pupil (ex, positive lambda)
- temporal to pupil (neg lambda, eso)
what is normal corneal reflex in Hirschberg?
about 0.5mm nasal to the center of pupil
