Intraday%20Variability%20of%20Control%20in%20Intermittent%20Exotropia

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Intraday Variability of Control in Intermittent
Exotropia

• Sarah R. Hatt, Brian G. Mohney, David A. Leske,
  Jonathan M. Holmes
• Mayo Clinic, Rochester, MN, USA

Commercial relationships None
2
Intermittent Exotropia - Control

• Poor control
• gt 50 of waking hours
• Deterioration consecutive visits
• indicator for surgery
• Type and degree of variability of control within
  1 day is not known
• Implications for
• defining severity
• interpreting change in control over time

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Purpose

• To assess the variability of control over one day
• in children with intermittent exotropia
• using control scale to quantify control

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Methods Control Assessment
Control Score Control Score Description
5 Constant exotropia during a 30-second observation period (before dissociation)
4 Exotropia gt50 of the time during a 30-second observation period (before dissociation)
3 Exotropia lt50 of the time during a 30-second observation period (before dissociation)
2 No exotropia unless dissociated (10 seconds) recovery in gt 5 seconds
1 No exotropia unless dissociated (10 seconds) recovery in 1-5 seconds
0 Pure phoria lt 1 second recovery after 10-second dissociation
Mohney BG, Holmes JM. An office-based scale for
assessing control in intermittent exotropia.
Strabismus 200614147-50.
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Control scale reliability

• near control k0.95 distance
  control k0.94

5
4
3
Investigator 2
2
1
0
0
1
2
3
4
5
Investigator 1
Scores differed by no more than one level on the
control scale Real change in control defined as
change of 2 or more levels on scale.
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Methods Intraday variability

• 13 children with intermittent exotropia
• (median age 8 years range 1 to 13)
• No convergence insufficiency type exotropia
• No co-existing ocular pathology
• No amblyopia

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Methods Intraday variability

• Examined 3 or 4 times over one day
• (minimum 2 hours apart)
• Control assessed using control scale
• Variable change in control 2 or more levels
  on control scale over day (distance or near)
• Stable no change in control over day

1031-1300
800 -1030
1301-1530
1531-1800
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Results Intraday variability of control
Stable control 7/13 (54)
Variable control 6/13 (46)
N13
7.2 years
7.3 years
Mean age
1
2.75
Median control - distance
1
1
Median control - near
30
26
Median angle - distance
Median angle - near
20
25
p0.04
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Results Variable distance control
Control scale rating
Assessment time
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Results Variable near control
Tropic
Control scale rating
Phoric
Assessment time
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Results Summary

• Control varies over one day in some patients with
  intermittent exotropia.
• Change occurs between spontaneous tropia and well
  controlled phoria.
• Worst control not always at the end of the
  clinical day.

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Change in distance control
5
4
Tropic
3
Control scale rating
2
Phoric
1
0
January
April
August
Assessment time
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Conclusions

• An isolated measure of control may be
  insufficient to represent
• baseline severity
• change over time.
• If control has a role in evaluating severity,
  multiple measures will be needed.
• Change in isolated measures of control should not
  be used for surgical decision making.

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Thank You
Supported by
Research to Prevent Blindness, Inc.