intermittent exotropia
Post on 07-May-2015
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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
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