3 - binocular vision

When do the eyes work together?

1. alignment

2. fusion

3. accommodation

What are the risk factors for strabismus?

1. premature birth

2. smoking during pregnancy

3. down syndrome

4. cerebral palsy

What are the two most common binocular vision disorders in kids?

1. convergence insufficiency

2. convergence excess

When do you test BV if patient has low entrance VAs?

test BV after refraction (if not cyclo'd) → otherwise (or in addition) have them back one month after adapting to specs

What should you directly observed to clue you into BV problems?

1. head turn

2. head tilt

3. chin tip

what is angle kappa?

distance between the center of the pupil and the light reflex

avg = ±5°

What can cause an esotropia appearance (pseudoesotropia)?

1. epicanthal folds

2. narrow IPD

3. deep set eyes

4. negative angle kappa → reflex appears temporally

What can cause an exotropia appearance (pseudoexotropia)?

1. wide IPD

2. positive angle kappa → reflex appears nasally

What is conducted first, angle kappa or Hirschberg?

Hirschberg

How is Hirschberg performed?

pt binocularly fixate pen light → look at position of light reflex

how to evaluate if eye is strabismic with Hischberg?

if position of light reflex is equal when binocular and monocular → normal

if binocular reflexes appear different than monocular → eye with monocular difference is strabismic

how to calculate the amount of strabismus with Hischberg and angle Kappa?

difference in light reflex position binocularly (Hirschberg) and monocularly (angle Kappa)

How is the krimsky test performed?

1. put prism in front of fixating eye

2. add prism until corneal reflex of deviating eye is same as angle kappa → this is the amount of tropia

What does the Bruckner test screen for?

presence of strabismus

How is a Bruckner test performed?

child fixates at direct ophthalmoscope (@1m) in dark room with both eyes → the brighter eye is strabismic

What causes false positives in the Bruckner test?

1. media opacities

2. posterior pole abnormalities

3. anisocoria (pupil size)

4. anisometropia

At what age can you start doing the Bruckner test?

starting around 9-12 months, when fixation starts to develop

Why do you not do the Bruckner test on a patient younger than 9 months?

1. 25% of children have fundus reflex differences up to 8 months of age

2. <2 months do not show fundus reflex dimming when fixating

What age do you we usually start attempting CT?

>1.5 years old

Who do we do cover test on?

any child that can fixate for a short period of time

what must you make sure to do when performing cover test if have an anomalous posture?

straighten kids head

What does the unilateral cover test check for?

presence of strabismus → moves on cover

What does the alternate cover test check for?

measures magnitude of phoria or strabismus

what tests sensory fusion?

stereopsis

what tests motor fusion?

fusional vergence

Stereopsis in an indirect indicator of _____________?

strabismus

what is global stereoacuity?

random dot steropsis

Which stereo acuity requires bifoveal fixation?

global stereo

what is local stereoacuity?

contour stereopsis

Which steroacuity can still be performed with small angle strabismus?

local stereo

What are examples of different kinds of global stereo tests?

1. stereo smile

2. PASS test

3. Random dot E

4. preschool randot

5. Frisby

6. Lang

What stereo test is a preferential looking test?

stereo smile → looking where pt looks

Which stereo tests are 2AFC (alternative fixed choice) tests?

1. PASS test

2. Random dot E test

If a test is 2AFC what score must they receive to move on?

3/4 or 4/4 correct

If a test is preferential looking, what score must the receive to move on?

only need to get it correct once

what is the Frisby stereotest?

pt identifies hidden circle

different thickness of glass causes differences in disparity → harder as plates get thinner

What are the levels of the Frisby stereotest?

340"

170"

55"

what is the Lang stereotest?

have cylindrical prisms over top of images so images dissociated → 3 images in triangle pattern

how to eliminate disparity in Lang stereotest?

turn 90°

What is the difference between the Lang I and Lang II stereo tests?

Lang 1 has no monocular target

Lan 2 has the star as a monocular target → everyone can see so can tell if malingering

what is a benefit for the Lang and Frisby stereotest?

no glasses necessary

What is the 10 pd BO test (reflex fusion)?

1. looking at near target

2. 10 BO over preferred eye

3. non-preferred eye abducts, then adducts

4. if both phases occur → then fusion, if abduct only → then no fusion

What does the 10 pd BO test (reflex fusion) test?

fusional vergence

What kids are prism bar vergences used for?

kids with steady fixation

How is NPC performed in a child?

same as an adult → just watch for convergence and break

how much accommodation should children have when testing amplitude of accommodation?

A LOT

How do we alter the push-up accommodative amplitude test for children?

1. use single target

2. may "pull away" (start super close and pull away until they can see what the target is)

How do we test for accommodative accuracy on children?

MEM retinoscopy

What is the test distance for MEM retinoscopy?

at the patients Harmen distance (elbows to knuckles, aka forearm length)

what is normal lag for MEM retinoscopy?

+0.50 to +0.75 → higher plus is more lag

how to test accommodative flexibility?

accommodative facility with Word Rock card and flippers