3. Most common form of XT
Onset: typically first few years of life
Most common symptoms
• Cosmesis
• Blur
• Astenopia
• Diplopia
• Monocular eye closure in bright sunlight
• None (suppression/ARC)
4. IXT: Clinical Characteristics
Intermittent fusion
Amblyopia is rare
Good stereoacuity at near, generally
When tropic, 1 of following:
• Diplopia
• Suppression
• Anomalous correspondence
5. 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
6. 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 findings
Problems with both
7. Control Score DescriptionControl 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
8. 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”
12. Intraday Variability
Examined 4 times over 1 day
8:00-10:30 / 10:31-13:00 / 13:01-15:30 / 15:31-18:00
Control assessed using control score scale
Variable
stable
13. Summary: Intraday Study of IXT Control
Control varied over
1 day in many
patients
Worst control not
always at the end of
clinical day
14.
15. 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
16. IXT: Other Diagnostic Evaluation
Consideration
Cycloplegic refraction
Cover test at remote distance
Sensorimotor evaluation
Distance Randot stereo test
Worth 4 –dot when tropia is manifest
Hering-Bielschowsky Afterimage Test when
tropia manifest?
19. IXT > 25-30 pd ???.... High recurrence rate
post-surgical ET and loss of stereopsis
Poor agreement on type of surgery
20. 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
