Heterophoria

Question 1

Normal binocular vision

Answer 1

-both eyes simultaneously cooperating with their bifoveal fixation to give a single perception of the pbject
-fusing images from the two eyes
Sensory fusion: Integration of similar images at the cortex
Motor Fusion: motor alignment to sustain binocular vision

Question 2

Motor Fusion

Answer 2

• tries to eliminate disparities of the two images
• tries to make images from each eye fuse as best as possible to make one image
• needs vergences to produce one image

Question 3

Convergence

Answer 3

-tries to maintain binocular vision by ensuring images are on corresponding retinal areas of each eye and there is no disparity between the images

Question 4

Heterophoria

Answer 4

• also known as phoria
• tendency of the eyes to deviate when fusion is blocked
• alternate cover test
• when there is binocular fusion, eyes are aligned on target
• with fusion, visual axes of both eyes intersect and fixate on target
• visual axes is from the fovea to the point of fixation

Question 5

Symptoms of Heterophoria

Answer 5

-can be abnormalities in binocular vision even though phoria is only there when fusion is broken
-symptoms occur when fusional amplitudes are not enough
Examples:
-convergence or divergence insufficiency or excess

Question 6

Maddox Rod Phoria

Answer 6

• Distance and Near
• with correction
• occlude right eye and only do right eye
• penlight at 40cm
• muscle light at distance
• TEST CANNOT DIFFERENTIATE A PHORIA AND A TROPIA

Question 7

Horizontal/ vertical phoria

Answer 7

• test both
• Horizontal phoria: ridges on maddox should be horizontal, light should be vertical
• Vertical phoria: ridges on maddox should be vertical, light should be horizontal

Question 8

What does the light mean??

Answer 8

• red line through light: Ortho
• Red line to the right of light: uncrossed diplopia(eso)
• Red line to the left of light: crossed diplopia(exo)
• Red line below light: right hyper
• Red line above: left hyper

Question 9

Uncrossed Diplopia

Answer 9

• eso deviation

- eye is deviated in, light hits NASAL retina and projects TEMPORALLY

Question 10

Crossed Diplopia

Answer 10

• exo deviation

- eye is deviated out, light hits TEMPORAL retina and projects NASALLY

Question 11

Supression

Answer 11

• active deactivation of a retinal image in one eye by the visual cortex
• brain will do this to decrease disparity

Question 12

Measure phoria with prism

Answer 12

• exo=BI
• eso=BO
• Right hyper=BU over left
• Left hyper=BD over left

Question 13

Expected findings

Answer 13

-Similar to cover test
1 prism diopter XP at D (+/- 2 diopters)
3 prism diopters XP at N(+/- 3 diopters)

Question 14

Modified Thorington Phoria

Answer 14

• use thorington cards at distance and near
• 10ft for distance, 40cm for N(scaling the card is different for D and N)
• hold penlight in holes of the card

Question 15

Hirschberg review

Answer 15

-angle lambda is angle between the corneal reflex and the center of the pupil
3 possible positions
1. center
2. Nasal to pupil(positive angle, exo posture)
3. Temporal to pupil (negative angle, eso posture)
-1 mm of deviation=22 prism diopters

Normal:
reflex at about 0.5mm nasal to the center of the pupil