Strabismus

Describe first, second and third degree targets when evaluating level and range of fusion

First degree - superimpose dissimilar targets Second degree - fusion common borders Third degree - stereopsis Want to test distance and near level and range

Hess Lancaster shows greatest separation looking up and left, as well as to the right. Lagging image in right eye. What are the paretic muscle(s)

Inferior oblique right eye And Right lateral rectus Primary angle is left eye fixating

What is suppression

Lack of perception of normally visible objects in all or *part of the field* of vision of one eye Occurs simultaneous stimulation of both eyes, attributed to cortical inhibition Latency is a thing! Benefit with flashing or blinking a lot to get through latency period

Recent onset diplopia after head trauma. With best optical correction alternative cover test, you measure 20 pd BI on OD fixating, 35 pd BI with OS fixating. What eye is affected with paretic muscle, and what muscle

Left eye (needs more correction) Left medial rectus (need BI prism for exo) Would expect greatest deviation in dextroversion

Maddox rod over left eye. Greatest separation up and left. Leading image is left eye What is the paretic muscle

Left superior rectus Red lens leads. Right eye is fixating here, but largest deviation for left eye

Is it easier for a patient to suppress with similar or dissimilar targets

Similar targets, harder to focus, more confusion - suppress

What should you note if a patient has anomalous correspondence

Type Amount Stability Frequency - what tests Depth

If a patient has nasal eccentric fixation, is their eso deviation usually over or under estimated

Underestimated deviation compared to true amount

Right esotropic patient views fixation point with right eye at 50 cm. After image is reported 1 cm to the left of fixation dot. What is eccentric fixation if normal correspondence

1 cm/.50 m = 2 pd eccentric fixation Right eye is fixating nasally if image tagging fovea is left

What do the circles represent on your direct's Visuoscopy target

1 prism diopter each Circle center counts as one diopter!

Patient notes MITT box has brush rotating 3 cm to the left of fixation dot. Patient is fixating with right eye. Test distance 1 metre What type of eccentric fixation is this, and what is her likely deviation

3 cm / 1 m = 3 pd eccentric fixation Right eye's target on left - nasal EF Likely esotrope

Patient has 3 pd of eccentric fixation. What is their expected VA's

3+1=4 4=MAR=1/snellen=x/20 Expect 20/80

Intermittent exotropia scale of control

5 constant XT 4 XT more than 50% of exam before dissociated 3 XT less than 50% of exam before dissociated 2 XT only after dissociation, recover more than 5 seconds later 1 XT only after dissociated, recover 1-5 seconds 0 XT only with dissociated, recover less than one second...phoria Have to observe for 30 seconds before dissociated to determine if need to dissociate or not (above or below grade 3)

Your 15 pd ET has 10 pd of divergence and 15 pd of convergence. What is their range of fusion

5 pd to 30 pd BO Starting at 15 BO d/t trope Divergence goes from 15 to 5 BO Convergence from 15 to 30 BO Not starting at zero!

Define paradoxical anomalous correspondance

After EOM surgery in patients who had already developed anomalous correspondence PAC 1: Angle of anomaly is greater than objective Subjective is opposite direction of objective, "negative" PAC 2: subjective is greater than objective, angle of anomaly is opposite direction of objective

How to measure objective angle of deviation on troposcope/synoptophore

Alternating flash technique with *first degree* slides Magnitude of manifest deviation, cosmetic difference from alternating cover test with full deviation

What to record when a patient has eccentric fixation

Amount Direction Steadiness Always monocular testing Foveal off center 0-1 deg Parafoveal 1-3 deg Paramacular 3-5 deg Peripheral >5 deg

What type of accommodation measurements should you make in constant strabismics

Amplitude monocularly only Facility monocularly only MEM Monocularly only applies also to intermittent strabs with high frequency of troping

What is really being measured on Hirschberg

Angle lamda pupil axis and line of sight (called angle kappa) Measured monocularly, 40 cm fixating on penlight Distance from *center of pupil* to Perkinje reflex in mm Nasal positive, temporal negative 1 mm is *12.5 degrees*, 22 pd

How does a strabismic patient achieve single simultaneous binocular vision despite the fact there is a deviation

Anomalous correspondance

Define anomalous correspondence

Anomalous correspondence - subjective and objective not equal

How do you record results of red lens test

As if looking at patient Like H test Right lateral rectus problem in image

How to assess control in a strabismic

BEFORE ANY DISSOCIATIONS (or ten minutes after cover test) Evaluate distance and near control 30 sec observation as patient fixates on *accommodative* targets If no strabismus observed, determine time to recover fusion after 10 sec dissociated - use *worst of three trials* covering each eye

How can you measure positive and negative fusional ranges on the synoptophore

BO patient pushes away, positive fusional vergence BI patient pulls in, negative fusional vergence

What tests can anomalous correspondence be measured in

Bagolini (most likely to find AC here bc binocular) Troposcope HBAIT

How to measure depth of suppression

Bagolini filter bar - in front of fixating eye, viewing light at distance, darker is more deep suppression Worth 4 dot, polarized 4 dot - suppressing in the dark is deep Troposcope - amount of illumination needed to stop suppression

History of a strabismic patient

Birth history - full term, complications, birth weight, APGAR Family history Onset of strabismus Frequency of their eye turn, progression Previous treatment Symptoms - depth, double vision, HA, blurry, asthenopia Cosmetic concerns, attitude of it (be nice)

Describe Bruckner test

Brightness of pupils from photo at 1 meter (pt older than 8 mo) Brighter eye is strabismus Equally bright eyes is normal alignment Anomalous results with *anisometropia*

A patient says the targets are floating on top of each other, but not superimposed. They just got hit in the head. What's happening

Central fusion disruption

What is anomalous correspondance

Cortical phenomenon of *binocular* vision in which stimulation of two foveas does not give rise to same subjective visual direction Fovea of fixating eye corresponds to area of anomaly in deviating eye Neural adaptation to misaligned eye where non corresponding retinal points linked in visual cortex for binocular fusion

How to perform Hess Lancaster screen

Dim or dark room Patient must not turn head Test distance 1 meter Record results for all 9 gazes, record fixating eye (if examiner has red laser, red filter is fixating) Locate direction of gaze with *greatest* separation - paretic muscle action field Lagging eye is the problem paretic eye

Important tips for objective angle measurement in strabismics

Distance and near in *all 9 cardinal positions of gaze* Cover test with *accommodative* target Ask questions of details

Important reminders for retinoscopy for strabismic

Dry and wet ret - use cyclopentolate or atropine Stay on axis!

If there is an interocular difference in angle kappa, what is this indicating

Eccentric fixation, if reduced acuities EF only happens monocularly!!! But easy to miss on Hirschberg bc minimum noticeable is 0.5 mm or 11 pd

Exo deviation is crossed or uncrossed on Hess Lancaster test

Exo is uncrossed bc this is a direct projection test, how the eyes actually are Red filter eye sees red *laser* target

Exo deviations would have crossed or uncrossed diplopia in red lens test

Exo sees *crossed* diplopia here bc leading image has paretic muscle in that eye Red lens leads, Lancaster lags (Eso is uncrossed diplopia)

Which eye is the fixating eye on cover test

Eye not behind prism If acute onset strabismus or suspected palsy, measure cover test with *each eye as fixating* Wouldn't expect same fixation amount if recent paresis

How to record suppression in a patient

Facultative - binocular/monouclar, uni, alternating, intermittent Size - foveal <1 deg, central 1-5 deg, peripheral >5 deg Deep mild or shallow (prism probably okay for mild but not deep)

Compare muscle action and field of action

Field of action is diagnostically where the muscle is the primary mover, H test results Muscle action is primary, secondary and tertiary actions; effect of muscle's contraction on rotation of the eye in *primary gaze*

How do first, second and third degree targets in synoptophore evalulate binocular vision tasks

First degree - angle of deviation and retinal correspondance Second degree - motor and sensory fusion, *suppresion* Third - stereo only d

What are the theories of anomalous correspondence

Innate origin, problem caused from early onset strabismus Sensory adaptation from strabismus, evolves from normal correspondance Motor adaptation of registered eye movements, communicating with peceptual area of brain for visual direction (version probs like strab) but normal correspondance with accommodative esotropes/non registered eye movements

How to perform 4 pd BO test

Looking for version then vergence Both eyes look one direction, then see convergence Atypical results for normal and abnormal BV patients though, don't rely on this alone more of a tie breaker

How to perform Haidinger brushes

MITT box has rotating propeller Instruct patient to look *monocularly* at direct center of cross, but point out where propeller brush is rotating Direction of brush rotating is where fovea is located Test at 50 cm or 1 meter for easy math of pd eccentric fixation

What does the simultaneous prism cover test measure

Manifest strabismus amount Actual strabismus they live with binocularly (alternating cover test measures larger, full strab) Neutralize/reversal movement by using prism and covering other eye at same time

If no spontaneous tropia is observed at distance, what is the next step when determining control of an exotropia

No trope at distance in observation, move to *near observation* 30 sec Then can occlude at distance - want to observe before any dissociations!!!

Define normal correspondance

Normal correspondence - subjective and objective angles are equal, angle of anomaly = 0

Describe covariation of angle of anomaly

Objective and angle of anomaly change when troping Subjective angle always zero, even if troping Typical with *intermittent exotropes* So they can fuse with normal correspondence, but when they trope they show harmonious correspondence

What are the three angles of correspondence

Objective angle - line of sight of deviating eye fails to intersect target (amt strabismus) Subjective angle - angle/amount of prism where patient perceives fusion; *changes with eccentric fixation* Angle of anomaly - difference between objective and subjective angles <A = <H - <S (Also angle zero, where object of regard is)

Eccentric fixation affects what angle in correspondence

Objective angle, your measurement is off because they're using a different point from fovea

Is there a greater deviation with tilt to the same side as original deviation for obliques or rectus palsies

Oblique palsies more deviation in tilt same side

Describe Krimsky test

Observing Hirschberg reflexes, use prism over *normal fixating eye* to align Perkinjes Make sure you're aligned centrally for patient If patient has a *range of fusion*, fusion may occur earlier than measured deviation

How do you perform Visuoscopy

Occlude one eye Ask patient to look at center star on direct target Where is fixation relative to fovea, note stability and how far off Try to avoid if patient is dilated, don't use red free

What tests allow suppression evaluation

Orthoscope Worth dot Polarized 4 dot 4 BO test Synoptophore Make sure to test central and peripheral!!

How to measure size of suppression

Orthoscope pie slices Troposcope size of 2nd deg targets Prisms - 4 directions until diplopia reported, no dissociating factors Hess lancaster screen, binocular perimetry, which direction Worth 4 dot or polarized 4 dot - distance to near

What should be noted on versions and ductions

Over action and under actions, grade 1 to 4 A/V patterns on up and down gaze Duane's retractions, palpebral fissure changes

How to perform red lens test

Patient cannot move head! Fixating eye is eye not using red lens Record results for all 9 positions of gaze, locate direction where *greatest separation* occurs - Action field of paretic muscle in acute deviation If fused, only see one red light If dissociated, see red and white light

When is after image transfer useful

Patient has normal correspondance with eccentric fixation Tagging the fovea, can't have anomalous correspondance for measurements!

When is Krimsky useful

Patient is blind in one eye or deeply amblyopic Measuring objective angle of deviation

Compare a positive and negative angle of anomaly

Positive <A is crossed separation of foveal tags, objective is larger Negative < A is uncrossed separation of foveal tags, subjective larger Both indicate anomalous correspondance with non-zero <A

What to record for level of fusion in strabismics

Presence of second degree fusion at objective angle, with some fusion range Presence of stereopsis with compensating prisms Differentiate between harmonious and normal correspondence with all fusion responses!!! (Unilateral cover test)

If your patient suppresses the right eye, how will they respond to the 4 BO test

Prism over right eye, no movement at all (within suppression zone) Prism over left eye, both eyes look right but no convergence noted in OD bc still suppression zone Testing central suppression

What is eccentric fixation

*MONOCULAR* fixation is not using central fovea for vision

How do you record cover test

As if you're looking at the patient, like red lens test

What tests measure subjective angle

Bagolini Troposcope Red lens test

What is the expected visual acuity if a patient is eccentrically fixating

EF + 1 = minimum angle of resolution MAR = 1/ snellen = x/20

When is the true deviation different from deviation measured

Errors in holding prism - not central, too far fromt he eye Eccentric fixation Stacked prisms same orientation Deviation is > 30 pd, patient is over 5 D of refractive error

How can you measure a patient's range of fusion

Troposcope Bar prisms

How can you calculate the true deviation if there is eccentric fixation

True deviation = measured deviation + eccentric fixation Just don't miss a strabismic patient who has eccentric fixation masking a manifest deviation!!! (Ortho)

Patient sees two lights on Bagolini. The lights are above the crossing of the lines. Right eye sees right light. What type of deviation do they have

Uncrossed diplopia is esotropia (eyes already crossed) Use BO prism to find subjective angle of correspondence

If patient has temporal eccentric fixation, is it usually an over or under estimate of their exo deviation

Under estimated deviation compared to true amount

Patient reports two lights on Bagolini underneath the crossing of the lines. Right eye sees right line. 15 prism diopters BI provides patient with one light, two lines. Unilateral cover test shows 5 pd exotropia. What type of correspondence is this

Unharmonious anomalous correspondence Subjective is not zero - anomalous Subjective smaller than objective - unharmonious (If no tropia, would be normal correspondence)

If a patient has an A pattern of exotropia, do they still have anomalous correspondence in up gaze compared to primary gaze

Yes! Anomalous correspondence still occurs anywhere in retina, any gaze Even after EOM surgery can still persist!!! controversial though

Can you have normal correspondence with strabismus

Yes! Objective and subjective must be equal Would have diplopia if no suppression

How do you determine objective and subjective angles on Bagolini

Add prism until one light with two lines bisecting This prism amount is subjective Then with prism in place, do unilateral cover test to determine if objective is equal or different from subjective

What points are commonly suppressed

Fovea and fixation spot straight ahead But wide range of suppression!

What should you note on cover test about a strabismus

Frequency - constant or intermittent Laterality - Right left or alternating Direction, amount

Define unharmonious anomalous correspondance

Fusion is perceived at an angle less than angle of deviation, but not straight ahead Subjective is not zero Objective is greater angle, bigger than subjective Caused from incomplete compensation, artifact or increase in deviation

How to perform Bagolini lenses

Glasses with notches pointing toward the nose Ask patient if they see two lines Ask patient how many lights they see Normal, no suppression - two lines cross at the light Only one line - suppression Two lights - subjective angle is not zero; add prism until bisecting lines

What tests measure angle of anomaly

Haidinger Brush After Image Test Bifoveal test of cuppers Hering Beilschowsky After Image Test (HBAIT)

Define harmonious correspondence

Harmonious anomalous correspondence - subjective is zero, despite having strabismus; objective = angle of anomaly They say they're fused, you find deviations on cover test

What should be included in an exam for strabismus

History Refractive error Objective angle *Comitancy* Level of fusion Suppression Correspondance Fixation Rule out pathology

A patient says the target gets closer then disappears. Wait it reappears on the other side of the target....kind of like magnets repelling each other, can't get them closer What's happening

Horror fusionalis Superimposition and second degree fusion is not possible j Note where target disappears and reappears

When would you only need to do one trial of dissociation

If patient is still dissociated after 5 seconds, hasn't recovered yet No need to do three trials bc this is the worst score they can get - since didn't trope in 30 sec observation Grade 2

How do you know if a patient has a comitant or incomitant deviation from red lens test

Incomitant if there is a field of gaze with largest separation, others vary

Does it matter if you use red or green filters over an eye for Worth dot test for suppression

Yes 20% of patients changed status based on which filter over the eye So be consistent and note in chart Also some filters let more light through than others

If you wanted to simulate near in the synoptophore, what changes would you make

Put in a -2.50 lens to accommodate for near amount 40 cm If pupillary distance was 60, zero point would be at *15 pd BO* with no other deviation

When is red lens test or Hess Lancaster appropriate for use

Recent onset strabismus, new palsy Not if anomalous correspondance or suppression But a chronic palsy can show less incomitancy, more contracture of muscles

When should you suspect eccentric fixation

Reduced VA's patient may have microtrope Constant strabismics

When is a patient's refractive error affecting the measurement of a deviation

Refractive error 5 diopters or more Deviation is 30 pd or more Plus lenses *decrease* measured deviation Minus lenses *increase* measured deviation (have to think of lenses as prism not magnification effect)

When is stacking prism worst

Same orientation Larger amounts of prism Angle is more accurate if prism in front of each eye

Describe anomalous fusional movements

Slower than true fusion Not as accurate Not slow enough to visibly see with naked eye

Who is more likely to get anomalous correspondence

Small intermediate angles < 10 pd Younger patients, newly strabismic

What indicates the primary angle in Hess lancaster

Smaller deviation field, paretic eye is matching/working - primary angle Will be *opposite* eye's *fixation* turn

What notes should you make about monocular fixation on cover test

Steady or unsteady fixation Wandering eyes Latent nystagmus

Patient reports two lines with one light in the center on Bagolini. You measure cover test as 10 exotropia. What is their correspondence

Subjective is zero Objective is -10 Angle of anomaly is -10+0= -10 Harmonious anomalous correspondence (<S=0)

How can you evaluate comitancy of strabismus

Subjectively: red lens test, Hess lancaster screen Objectively: cover test in 9 fields of gaze (changes 5 pd or more, each eye fixating), Park's 3 step test Rely on cover test, especially if anomalous correspondance

If visual acuity is reduced with strabimsus, how should you run the exam

Test VA's with pinhole Evaluate for eccentric fixation - calculate expected VA's from this Rule out pathology

How to perform after image transfer

Test distance 50 cm or 1 m Occlude deviating eye Flash normal eye, then cover it Using deviating eye, have patient fixate on a target Ask where the flash image is - indicates eccentric fixation bc image is tagged fovea

When is Park's three step of good use

Vertical deviation present, determine if it is comitant

What direction should you flash a patient in after image transfer if they have nasal eccentric fixation

Vertically flash - easier to line up If superior or inferior eccentric fixation, can flash horizontally