Intraday Variability of Control in Intermittent Exotropia

1. 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. Poor control: > 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 Intermittent Exotropia - Control

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

4. Methods – Control Assessment Mohney BG, Holmes JM. An office-based scale for assessing control in intermittent exotropia. Strabismus 2006;14:147-50.

5. 5 4 3 Investigator 2 2 1 0 0 1 2 3 4 5 Investigator 1 Control scale reliability near control k=0.95 distance control k=0.94 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.

6. 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

7. 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 8:00 -10:30 10:31-13:00 13:01-15:30 15:31-18:00

8. Results – Intraday variability of control N=13 Variable control 6/13 (46%) Stable control 7/13 (54%) Mean age 7.3 years 7.2 years Median control - distance 2.75 1* Median control - near 1 1 Median angle - distance 26^ 30^ Median angle - near 25^ 20^ * p=0.04

9. Patient 1 Patient 10 5 Patient 13 Tropic 4 3 2 Phoric 1 0 8:00 -10:30 10:31-13:00 13:01-15:30 15:31-18:00 Results – Variable distance control Control scale rating Assessment time

10. Patient 3 5 Patient 5 Patient 11 4 Patient 13 3 2 1 0 8:00 -10:30 10:31-13:00 13:01-15:30 15:31-18:00 Results – Variable near control Tropic Control scale rating Phoric Assessment time

11. 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.

12. 10:30 12:45 14:49 Change in distance control 5 Tropic 4 3 Control scale rating 2 Phoric 1 0 January April August Assessment time

13. 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.

14. EY015799 (JMH) Thank You Supported by: Research to Prevent Blindness, Inc.