Intermittent Exotropia: The Nuts and Bolts

Enayatollah Osroosh, student of Msc, Mashhad University

ACKNOWLEDGEMENT

Susan A, Cotter, OD, MS for use of data

slides.

Most common form of XTOnset: typically first few years of lifeMost common symptoms• Cosmesis• Blur• Astenopia• Diplopia• Monocular eye closure in bright sunlight• None (suppression/ARC)

Intermittent Exotropia

IXT: Clinical Characteristics

Intermittent fusionAmblyopia is rareGood stereoacuity at near,

generallyWhen tropic, 1 of following:• Diplopia• Suppression• Anomalous correspondence

Divergence excess• Far > near angle: high AC/A• True vs. psuedo (simulated)

Basic• Near = far angle; normal AC/A

Convergence insufficiency• Near > far angle; low AC/A

IXT Classification

Follow/Treat How can we tell if a patient is getting worse or better?

Determine magnitude under dissociated conditions?

Or frequency ?• Ask parents• In-office cover test findingsProblems with both

IXT

Control Score Description Control Score

Observed during 2 30-sec periods, first distance ,then near

Constant XT during a 30-sec observation period (before dissociation)

5

XT > 50% of the time during a 30-sec observation period(before dissociation)

4

XT < 50% of the time during a 30-sec observation period(before dissociation)

3

Worst of 3 consecutive trials of covering 1 eye for 10 sec at both distance and near

No XT unless dissociated(10 sec):recovery in >5 sec

2

No XT unless dissociated(10 sec):recovery in 1-5 sec

1

Pure phoria: < 1 sec recovery after 10-sec dissociation

0

Mohney/Holmes Control Score

Prior to dissociation, observe for 30 seconds:• Constant XT= Grade 5• XT > 50% =Grade 4• XT < 50% = Grade 3

Score distance and near fixation separately

If Not spontaneously Tropic….Move to standard dissociation phase of testing to

time “ recovery”

IXT Control Score

Example of Measuring Control of IXT

1..2..3..4..5..6..7..8..9..10..11..12..13..14..15..16..17..18..19..20..

21..22..23..24..25..26..27..28..29..30..

XT For 10 of 30Sec (33% of 30 Sec) <50% control score=3

1..2..3..4..5..6..7..8..9..10..11..12..13..14..15..16..17..18..19..20.. 21..22..23..24..25..26..27..28..29..30..

Step2:repeat 30 second observation before dissociation at near

1-2-3-4-5-6-7-8-9-10

...1-2-3

4 Second

1-2-3-4-5-6-7-8-9-10

1-2-3-4-5…

6Second

score1 score2

Intraday VariabilityExamined 4 times over 1 day8:00-10:30 / 10:31-13:00 / 13:01-15:30 /

15:31-18:00Control assessed using control score scaleVariablestable

Summary: Intraday Study of IXT Control

Control varied over 1 day in many patients

Worst control not always at the end of clinical day

How about Distance Stereoacuity?

Summary- How to Measure IXT?

Alternate cover test-dose not assess “control”

Control-problem of “sampling”-one assessment is not enough

Distance stereoacuity –need multiple measures

Near stereoacuity – often “good” anyways

IXT: Other Diagnostic Evaluation ConsiderationCycloplegic refraction Cover test at remote distanceSensorimotor evaluationDistance Randot stereo testWorth 4 –dot when tropia is

manifestHering-Bielschowsky Afterimage

Test when tropia manifest?

Management of IXT

Monitor Refractive correction Occlusion Over-minus lens Prism Vision Therapy Surgery

uncorrected ametropia?

equally accommodative accuracy

Discourage suppression

Promote sensory fusion

Moderate/high hyperopia consideration?

IXT: Refractive Correction

IXT > 25-30 pd ???.... High recurrence rate

post-surgical ET and loss of stereopsis

Poor agreement on type of surgery

EOM Surgery for IXT

Uses feedback techniques/procedures to improve fusional vergence & sensory fusion

Goal is not to decrease magnitude, but to decrease frequency and increase “control”

Active Vision Therapy

XT: Sequential VT Plan Phase 1: optical correction

Phase 2: monocular function Phase 3: improve Sensory fusion

Gross convergence

Fusional vergence

Anti-suppression therapy, including diplopia awareness when XT

Phase 3: Establish & improve normal Sensory fusion at orthoposition

Convergence surprise

Pencil push up

Brock string

3.dot card

Goal: Voluntary Convergence

Gross Convergence

Fusional Vergence Training

accommodation control

Smooth fusional vergence

Increase Fusional VergenceStep fusional

vergence

Increase Vergence Facility

Move From Near-Intermediate-Far

3 to 2 to 1

Monitor Suppression During active therapy

with suppression check

Can use filters for

passive TV watching

Anti-suppression Therapy Pathological diplopia

Use Red & Green filter in a dark room

Flash light, Penlight, Candle

Prism insertion/removal

Thank You