Heterophoria Flashcards
Normal Binocular Vision:
both eyes simultaneously cooperating with their bifoveal fixation to give a single perception of the object
Sensory fusion
integation of similar images at the cortex
This is what the brain does with the information
Motor fusion:
Motor alignment to sustain binocular vision
suppression –> scotoma
Motor fusion tries to ____ of the 2 images
eliminate disparities
It tries to make images from each eye _____ to make one image
FUSE as best as possible
Motor fusion _____ to produce 1 image
needs vergences
Convergence tries to maintain binocular vision by ensuring images are on ___________ so there is no disparity between the images
corresponding retinal areas of each eye
I.E. NPC is the closest distance where the eyes can converge and maintain binocular vision
Cover-Uncover Test (Unilateral Cover Test) helps to differentiate:
- presence of a deviation
- laterality/which eye (unilateral or alternating)
- frequency of the deviation (constant or intermittent)
Alternating Cover Test is used to determine
- direction of phoria or tropia
- magnitude (size) of the deviation
Which Cover Test is performed first?
Cover-Uncover Test (Unilateral Cover Test)
Do you perform cover test at near, distance or both?
Both
A phoria is seen on _____ because fusion is broken
alternate cover test
An alternating tropia means
either eye can fixate on the target
_____ is a tendency of the eyes to deviate when fusion is blocked.
Heterophoria (phoria)
When there is binocular vision and fusion on a target, both eyes will be
aligned on the target
Binocular Single Vision is when
the visual axes of both eyes intersect and fixate on the target (as long as there is fusion)
Visual axes is from
the fovea to the point of fixation
Even though a phoria only occurs when fusion is broken, there could be ______ in the binocular vision with a heterophoria
abnormalities
True/False: A patient may appear aligned, but there could be underlining abnormalities in the ability to keep fusion.
True
Symptons associated with a heterophoria may occur when/if
fusional amplitudes are not enough
Give examples of Heterophoric abnormalities:
- Convergence Insufficiency
- Convergence excess
- Divergence insufficiency
- Divergence excess
How can a phoria be identified?
Phorias can be identified and measured during a cover test or with a maddox rod
What is a maddox rod used to measure?
Horizontal and Vertical phorias at distance and near
What does the maddox rod do?
dissociates the eyes
Maddox rods can also be ___
white
