1. Commercial relationships: None Intraday Variability of Control in Intermittent Exotropia Sarah R. Hatt, Brian G. Mohney, David A. Leske, Jonathan M. Holmes Mayo Clinic, Rochester, MN, USA

2. Intermittent Exotropia - Control 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

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 Control Score Control Score Description 5Constant exotropia during a 30-second observation period (before dissociation) 4Exotropia >50% of the time during a 30-second observation period (before dissociation) 3Exotropia <50% of the time during a 30-second observation period (before dissociation) 2No exotropia unless dissociated (10 seconds): recovery in > 5 seconds 1No exotropia unless dissociated (10 seconds): recovery in 1-5 seconds 0Pure phoria: < 1 second recovery after 10-second dissociation Mohney BG, Holmes JM. An office-based scale for assessing control in intermittent exotropia. Strabismus 2006;14:147-50.

5. Control scale reliability near control k=0.95 distance control k=0.94 Investigator 2 Investigator 1 0 1 2 3 4 5 012345 Investigator 2 Investigator 1 0 1 2 3 4 5 012345 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 10:31-13:008:00 -10:3013:01-15:3015:31-18:00

8. Results – Intraday variability of control Median angle - near 30^26^Median angle - distance 11Median control - near 20^25^ 1*2.75Median control - distance 7.2 years7.3 yearsMean age Stable control 7/13 (54%) Variable control 6/13 (46%) N=13 * p=0.04

9. Patient 1 Patient 10 Patient 13 Results – Variable distance control Assessment time Control scale rating 0 1 2 3 4 5 8:00 -10:3010:31-13:0013:01-15:3015:31-18:00 Tropic Phoric

10. 0 1 2 3 4 5 8:00 -10:3010:31-13:0013:01-15:3015:31-18:00 Patient 3 Patient 5 Patient 11 Patient 13 Results – Variable near control Assessment time Control scale rating Phoric Tropic

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. Change in distance control 0 1 2 3 4 5 JanuaryApril August Assessment time Control scale rating Tropic Phoric 10:3012:4514:49

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