Heterophoria Flashcards
Normal Binocular vision:
Both eyes simultaneously cooperating with their bifoveal fixation to give a single perception of the object
Sensory fusion of binocular vision
Integration of similar images at the cortex
Motor fusion of binocular vision
Motor alignment to sustain binocular vision
Motor fusion tries to ________ ___________ of the two images and _____ ___________ to produce one image.
Eliminate disparities, needs vergences
NPC is:
The closest distance where the eyes can converge and maintain binocular vision
Two types of cover tests
Cover-uncover test
Alternating cover test
Cover-Uncover test
Presence of a deviation (Phoria or tropia)
Lateral its/which eye (unilateral or alternating)
Frequency of the deviation (constant or intermittent)
Alternating cover test
Direction of the Phoria and tropia
Magnitude (size) of the deviation
Which cover test is done first?
Cover-uncover
Are cover test done at distance or near?
Both
On cover-uncover, will you see phoria or tropia?
Tropia
On alternating cover test, will you see phoria or tropia?
Phoria
Because fusion is broken
What does alternating tropia mean?
Either eye can fixate on the target.
What is heterophoria?
Aka Phoria
A tendency of the eyes to deviate when fusion is blocked.
When there is binocular vision and fusion on a target, both eyes are aligned on the target.
..When there is something to focus on, there is no tendency to deviate..
The visual axes of both eyes intersecting and fixating on a target created what?
Fusion, binocular single vision
Visual axes extend from..
The fovea to the point of fixation
Even though Phoria occurs when fusion is broken, there can still be ____________
Abnormalities in the binocular vision
Symptoms associated with a heterophoria could occur if _________________________
Fusion all amplitudes are not enough
Heterophoric abnormalities
Convergence insufficiency
Convergence excess
Divergence insufficiency
Divergence excess
Phorias and tropias must be measured at:
Distance and near
How can phorias be measured and identified?
During cover test or with a Maddox rod
Maddox rods are used to measure what?
Horizontal and vertical Phoria at distance and near
What does the Maddox rod do?
Dissociates the eyes
What items are needed to test Maddox Rod Phoria?
Penlight
Handheld Maddox rod
Prisms
At what distance must near testing for Maddox rod Phoria be done?
40 cm
For horizontal Phoria, the Maddox rods’ grooves are oriented:
Horizontally
To give a vertical streak
For vertical Phoria, the Maddox rods’ grooves are oriented:
Vertically
To give a horizontal streak
During Maddox rod Phoria, patient must look at:
The white light and be aware of the red streak
If the red line is thought the white light,
Ortho
If the red line is to the right of the light,
Uncrossed diplopia, eso
If the red line is to the left of the light,
Crossed diplopia, exo
If the red line appears below the light,
Right hyper
If the red line is above the light,
Left hyper
The pt must hold the Maddox rod over what eye?
Right eye
Uncrossed diplopia is ___ deviation because:
Eso, because the eye is deviated in, the light hits the nasal retina and projects temporally
Crossed diplopia is ____ deviation, because:
Exo, because the eye is deviated out.
Light hits the temporal retina and projects nasally, across and beyond the visual axis of the fixating eye.
What is suppression?
The active deactivation of a retinal image in one eye by the visual cortex
The brain prefers to suppress (shut off imaging in an eye) to do what:
Provide vision as close to binocular vision as possible instead of: Any image disparity Blurred vision Diplopia Confusion
What is alternate suppression?
Alternating which eye is being suppressed,
For ex,
See 2 dots then 3 dots during W4Dot
How do you measure the size of the Phoria?
With a prism bar
If exo,
Use BI
If eso,
Use BO
For R hyper,
Use BU over OS 9since Maddox Rod is over OD)
For L hyper,
Use base down over OS
What is modified thorington Phoria?
Same as Maddox Rod Phoria, but thorington cards are used for distance and near.
Penlight is held through the middle of the card, and pt describes where the red line is
What is angle lambda?
The angle between the corneal reflex and the center of the pupil
Hirschberg
3 possible corneal reflex positions (Hirschberg)
Center of the pupil
Nasal to the pupil (positive angle lambda)
temporal to the pupil (negative angle lambda)
1 mm of estimated deviation from the relative point =
Approximately a deviation of 22 prism diopters
