List the components of strabismus exaM

What ocular motility testing should be done?

What other tests should be done in addition to CT?

What sensory evaluations should be done?

-HX, VA, CT (distance and near w/ prism, in other suspect positions with incomitant strab, Krimsky test with poor VA and poor fixation)

-comitant vs. incomitant, versions vs. ductions, 3 step-test, Hess- Lancaster, foced ductions, double-maddox rod (cyclotorsion)

-stereopsis, synoptophore, Worth 4 Dot, BSL, AI

-cycloplegic retinoscopy

-dilated fundoscopy

What is the objective motor testing we use?

What are the things this test does?

Requires what?

-CT

-quantifies the deviation

-detects ocular motility disturbances

-requires minimal patient cooperation

What is the purpose of subjective oculumotility testing?

What kinds of questions are asked?

-determines what adaptations, if any, the patient has made to adjust to the strabismus

-in regard to the way the patient integrates the information and how this information is subjectively determined

-establishes functional prognosis

-assists with treatment decisions

-determines the possible time of onset and duration of teh strabismus

-may be more accurate than subjective findings in some cases

-complex- too many tests and diff tests may give diff results

-not valid and/or reliable with younger patients

-requires an alert and communicative patient

-can obtain the same info with objective testing in some cases

-presence of absence of visual confusion and/or diplopia

-presence and/or absence of suppression

-presence and/or absence of amblyopia

-type of inter ocular relationship (retinal correspondence)

-response to disparate stimuli (stereopsis)

What are the 2 types of physiological supperssion?

What are these a property of?

-retinal rivalry and physiological diplopia

-NBV

How is retinal rivalry described?

What happens in physiological diplopia between the eyes?

-if 2 very different images are presented to the 2 foveas, the brain suppresses one or the other

-images outside of Panum's area are suppressed

What is visual confusion?

Is this a clinical concern?

In which eye does suppression occur?

Why might visual confusion also not be a clinical concern?

-dissimilarly contoured images fall on the foveas and are seen in the same visual direction 

-not usually thanks to retinal rivalry (ignores a fovea)

-at the fovea of the deviating eye regardless of age, supposedly*

-the clinician fails to ask the appropriate questions regarding clinical confusion

How is diplopia described?

What kind of diplopia does ET cause, crossed or uncrossed? How about XT?

Which image is not as clear? Why? What must be absent in order to have diplopia?

In XT, will the diplopia be more problematic with targets at distance or near?

-similar images fall on non-corresponding areas and are seen in different visual directions

-ET= uncrossed (homonymous) ; XT= crossed (heteronymous)

-the target seen by the deviating eye because it is extrafoveal; suppression must be absent

-targets at near

Why does suppression develop in strabismus?

Is the entire retina of the deviating eye suppressed?

Can supprression exist in isolation, i.e. without an apparent cause?

-to eliminate diplopia

-no, there is a region or zone of suppression that develops (point zero to fovea)

-no, there is always a cause*

-regional

-facultative and contingent on manifestation of the strabismus

-requires similar contours

-has a latent period

-age dependent (like amblyopia)

What does regional suppression mean?

What shape is this generally?

Is one eye ever totally excluded from vision?

What determines the size of the suppression zone?

What would happen if over-correcting prism was placed on the strabismic eye that placed the image outside of the suppression zone? Why is measurement this useful?

How does this concept relate to EOM surgery? What migh happen if the patient is young when this occurs?

-usually confined to a specific retinal location (suppression zone)

-hemi-retinal area

-no

-the magnitude of the strabismus

-pt would experience diplopia

-can determine how large the suppression zone is

-if surgery over-corrects the deviation, pt will experience diplopia after sx; could develop another suppression zone due to the new deviation and diplopia

What is meant by the statement "suppression is facultative"?

What is meant by the statement that "suppression is contingent on presence of strabismums"?

Why does suppression usually take place when there are similar contours? How is a red lens used here?

-exists only during binocular veiwing

-there is only suppression when the strabismus is manifest

-because with dis-similar contours it is harder and less likely that suppression will occur

-a red lens makes the images different and harder to suppress because a red filter dissociates

What is meant by the statemnt that suppression requires a short latent period?

How might this be demonstrated clinically?

What do you expect with longer expsoure to a stimulus in the suppression zone?

-if an image falls on a suppression zone and the exposure is short, the suppression may not become manifest (pt will have diplopia)

-slowly covereing and uncovering the eye of a strabismic patient may cause transient diplopia

-likley to suppress the image

How is suppression "age dependent"?

What do you suspect if you have an adult patient with a constant ET, yet they do not experience diplopia?

-develops supposedly* only in young and visually immature patients

-that is developed in childhood

In terms of suppression, what might happen to the suppression zones in an alternating strabismus?

Is this always the case?

-suppression zone may transfer from OD to OS in an alternating strab?

-no

What are 6 tests that can be used to test for suppression?

Which is the only objective test?

What might this be more useful for when compared to CT?

When might the 4 BO test also be +?

-4 BO prism test

-Worth 4 Dot

-Synoptophore

-Bagolini striated lenses

-stereopsis

-bangolini filter bar

-Worth 4= objective

-picking up a microtropia

-organic lesion or anisometropia

For the 4 BO test, which eye should you watch?

What do you expect to see if there is no suppression?

What do you expect to see if the prism in place in front of the eye that is suppressed?

What do you expect to see if the prism is placed in front of a normal eye, if the other eye has suppression?

-the one w/p prism

-both eyes will move in the direction of the apex of the prism and then the eye w/o the prism will move toward the nose

-the eyes will not move at all

-both eyes will shift toward prism apex, and suppressed eye (eye w/o prism) will not move back toward the nose

What angle does the distance W4D test subtend on the retina?

What angle does the near W4D test subtend?

Which distance tests bifoveal fusion (central suppression) and which distance tests peripheral fusion?

Do you expect a patient who suppresses at distance to also suppress at near? ***This is why it is said that fusion is not all-or-none!!!

-an angle of ~1.25 degrees

-an angle of ~ 6 degrees

-distnace= central/bifoveal and near= peripheral

-not always, will not suppress if they have maintained peripheral fusion

How should the W4D test be performed in terms of distance? Where should you start?

At what distance is suppression usually found?

-start at near and then slowly move to distance

-2-5 ft from the spectacle plane

With Bagolini striated lenses, what might you expect your patient response to be for the following situations?

-no suppresion?

-central/partial supperssion? Example- patient has central suppression in the left eye?

-total suppression?

-diplopia? In what cases is this result most likely to happen?

-an X that crosses in the middle

-an X that has missing parts to some of the lines- the line seen by the left eye will have part of it missing where it should cross in the middle, but still have part of the line farther out toward the periphery

-only one line seen by one eye

-two crossed lines that cross above or below where the center of the X should be; most likley to occur in recently acquired strabismus

How does local or contour stereopsis work?

What is a distadvantage to this testing?

How does global or random dot stereo testing work?

If patients have ___ stereopsis they will also have ___ stereopsis; however a patient with ___ stereo may not have ___ stereo

This means that ___ stereo is the most sensitive

-localized features of objects are extracted from a visual scene and are assigned relative depth values allowing fusion of a single dot or line segment

-have some monocular depth cues

-target consists of computer generated random arrangement of dots w/o information about form or depth- fusion of a set of binocular dots or lines

-global, contour; contour, global

-global 

What are the 2 indications of change in stereopsis over time?

In which condition has deterioration in stereoauity after treatment actually been shown as a sign of improvement?

-either a sign of improvement or deterioration 

-XT

What are the 8 different types of stereo tests we learned about in class?

Which 2 tests do not need glasses? Why?

Which 2 tests are screeners?

Which 3 are global only?

Which one requires red/green glasses?

-Randot stereo test, Random dot E stereo test, TNO stereotest, Frisby stereotest, lang stereotest, preschool Randot stereotest, distance stereotest- BVAT, and distance stereotest (distance Randot stereotest)

-Lang stereotest; dissociates the eyes with small cylinders like Maddox rod; Frisby test- stereo created by thickness of the plates

-Random dot E, Lang

-TNO, Lang, Preschool Randot (PEDIG)

-TNO

Fun Fact- What does TNO stand for?

What is a disadvantage to the Frisby? This test is also partially what type of stereo?

The lang test if purely ___ stereo?

-The Netherlands Optical Society

-may also have monocular cues; global

What test can be used for distance stereopsis?

This tests what kind of stereo, contour or global?

Results of the Rutstein Corliss study showed that which type of stereo is most sensitive?

At what distance should the distance stereotest be held from the patient? How is this test different from the B-VAT?

-the binocular visual acuity tester (B-VAT)

-both global and contour

-distance global

-3 m

-purely global and easier

What does the bangolini filter bar allow you to determine about the suppression?

What do you conclude if the patient's suppression resolves with a minimum density filter?

-the depth of the suppression

-that the suppression must not be very deep

In variables of suppression, when the fixating eye alternate from OD to OS, what happens to the suppression usually?

What is the exception?

Why does this happen?

What is this known as?

-the suppression zone transfers from eye to eye in most cases to prevent diplopia

-seen occasionally in adults with childhood onset strabismus (when fixate with the eye that was originally deviated, they get suppression; when they fixate with the eye that was not originally deviated there is no supperssion)

-they cannot alternately suppress

-fixation switch diplopia

What are the 3 causes of fixation switch diplopia? 

How should you Rx for adult patients with childhood onset strabismus? 

How long may it take before they notice onset of diplopia in these cases?

-RE change, cataract in the dominant eye, iatrogenic (monovision CLs, refractive surgery, IOLs)

-judiciously

-up to 3 years

Does the absence of diplopia in an adult patient with strab always indicated suppression?

Why does this happen? When is it most likely to happen?

How can these patients be made diplopic clinically (3 ways)?

Ignoring is a ___ process; the patient learns to ignore or disreagrd the image- not suppress it!

What do you suspect to happen if you do alternating occlusion on this type of patient?

-no, does not always show that it was developed in childhood

-patient learn to disregard/ignore the diplopic image; more common if dev image is out in periphery

-using under-correcting prism, rapid alternate occlusion, minimal density filter

-physiological process

-they will become diplopic

How does a red lens affect suppression when placed over the deviating eye?

When using the red lens OD on a 20 PD ET OD patient what are the 4 possibile responses?

What does presence of a pink light indicate?

What does presence of only one light indicate?

-it disrupts the suppression zone- harder to suppress casuing diplopia

-sees 2 lights, red to the right, sep by 20 PD

-sees 2 lights, red to the right, sep by 10 PD

-patient sees 1 "pink" light 

-patient sees either one red or one white light

-fusion

-suppression

If during the red lens test the patient responds that they see 2 lights, red to the right, measured at 20 PD what do you suspect about their foveal interaction?

If patient reports that they see 2 lights, red to the right, and they are 10 PD away, what do you suspect? 

-foveas correspond to each other- NRC

-fovea of the left eye corresponds to an area outside of the fovea of the right eye- ARC (harmonious)

When does ARC happen?

What happens to the relationship between the 2 foveas in this condition?

This relationship causes what to happen?

What does this imply?

-during visual immaturity 

-it is loosened and there is a shift in the visual direction of the non-fixating eye

-the fovea of the fixating eye acquires and ARC with a non-foveal point on the retina of the deviated eye

-the 2 foveas no longer have a common visual direction

What are the 2 definitions od ARC?

In the case os a small strabismus, what does this represent?

ARC= what?

-the 2 foveas have 2 different visual directions

-the fovea of the fixating eye has acquired an anomalous common visual direction with a peripheral area of the deviating eye

-an effort to restore some BV status

-BV in the presence of manifest strabismus

What are the 3 angles measured in ARC and what are their definitions?

At what valur does angle A become clinically significant?

-Angle H- ojective angle of the deviation found on CT (zF)

-Angle S- subjective angle, or angular separation between diplopic images of a single target (za)

-angle A- angle of anomaly- the difference between H and S (aF*)

-> 4 PD

What do the points z, F, and a stand for?

In NRC angle H is >/</= to angle S, and angle A equlas ____?

In unharmonious ARC (UHARC), angle H is >/</= angle S, and angle A is >/</= to ____?

In harmonious retinal correspondence, what happends?

What are the anlge relationships in this condition? What size deviations is this best and allows what?

-zero measure point

-fovea

-point of anomaly

-equal to; zero

- does not equal; greater than 0

-there is the possibility of fusion?

-H does not equal S, and H=A

-small angle, allows rudimentary fusion

Does UHARC exist? What might it actually be?

What is UHARC caused by?

How might an ET respond to testing if there is a decrease in the subjective angle with ARC?

-?- could be artifact of synoptophore testing or an intermediate stage between NRC adn HARC

-an increase in the objective angle (angle H), or a decrease in objective angle 

-UHARC and they will now respond to testing like an XT with crossed diplopia

What might be seen in alphabet patterns in HARC?

What are horror fusions?

What condition is this associated with?

-covariation in alphabet patterns (HARC is maintained)

-inability to obtain binocular superimposition of haploscopically presented targets or the condition in strabismus where targets approachign each seem to jump or slide past each other other w/o apparent fusion or suppression

-intractable diplopia

What might be the cause of horror fusions? (4 causes)

Which is the most common cause?

In the case of cataracts when does this occur in terms of sx? why does this happen?

-over-zealous VT/orthoptics because suppression has been broken down

-strab sx (most common)

-idiopathic

-acquired unilateral cataract in adults with a childhood onset strabismus  (intractable diplopia occurs after cataract surgery); in long-standind cataract disrupts prior suppression

What might be a differential diagnosis for horror fusions?

How is this tested?

What are the txts for horror fusions?

What does this allow?

-cyclotorsion- with synoptophore

-aniseikonia

-bangerter filters or reverse prism- allows the patients to ignore the diplopic image by using a density filter or putting the image farther out in the periphery

What are the 4 tests for retinal correspondence?

Which is the preferred test?

What is the prefered test for stereopsis?

-red lens test (rarely used(

-synotophore (prefered test for RC)

-W4D

-bangolini striated lenses

-Randot

If in ARC the H and S differ by >/= ___ PD, stop testing. 

If patient has NRC, test ___, etc. 

What might interfere with W4D testing at distance?

If a patient has ARC, what might you expect them to report on the W4D test at near?

If there is movement on CT with compensating prism it is __RC, if there is no movement with compenstating prism on CT, then it is __RC.

-4

-fusion

-suppression

-4 dots

-ARC, NRC

With Bangolini striated lenses on a patient with a constant strab, what do you suspect from the following pt responses?

What test is also performed with this one?

-an X that crossed in the center- ARC

-an X with the line of one eye missing near center of the X- partial suppression

-only one line- large angle strab

-unilateral cover test

What tests measure the angle of anomaly direcly in ARC?

Which is the preferred test?

What anatomical retinal area are we targeting with these tests?

-Hering Bielschowsky  AI test

-Hadinger brush AI test

-Hering B test

-fovea

In the Hering B test, what will the patient report with an ET? An XT?

How common is it that the EF= the point of ARC?

How will a patient report this on hadinger brushes?

If the patient reports that the brushes are on top of the fixation point and the AI is to the left or right of these, what do you suspect?

What do you suspect if the patient reports that the brushes, AI, and fixation point are all together

Can you meausre the angle of anomaly using the Hadinger brushes in ARC?

-crossed lines (right eye image on left, and left eye image on right); opposite for XT

-very rare

-the AI will be through the fixation point and the brushes will be to the right or left of these 

-ARC, CF

- NRC, CF

-yes

Which test is best at picking up a superficial ARC?

Why?

Which tests pick up moderate ARC?

Which tests pick up deep ARC?

-Bangolini lenses- supposefly easier to reverse the ARC (less dissociative)

-Bangolini lenses and synoptophore

-bangolini lenses, snyoptophore, and AI- harder to reverse the ARC and more dissociative

What 3 conditions favor development of ARC?

In which strabs might you also find ARC, but this is not clinically significant?

-young age (>/= 4)

-small to moderate size strabismus

-stable strabismus

-intermittent and incomitant strabs

What are the 3 components of BV in ARC?

A fusional movements true or are they just covariation?

In which patients is stereopsis more likley?

Do you expect high stereo in these patients?

-fusional movements

-covariation

-stereopsis

-we don't know

-less than 5 PD strab with superficial ARC

-no