The primary outcome measure was deterioration of the intermittent exotropia (IXT) within 6 months after randomization. Motor deterioration was defined as a constant exotropia of 10 D or more at distance and near by SPCT, confirmed by a retest, during any masked examination between 3 months and 3 years after randomization.

Stereoacuity scores (seconds of arc) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

A logarithm base 10 transformation was used to convert stereoacuity scores to the log scale to calculate descriptive statistics (reported as log of seconds of arc, or log arcsec). The stereoacuity at near is reported at 3 years, as is the change in near stereoacuity from baseline to 3 years. Both were reported as log of seconds of arc, or log arcsec.

Outcome based on initial testing regardless of whether a retest was completed for suspected deterioration. Change is calculated as baseline level minus 6-month level. For change in stereo, positive change indicates improvement in stereo.

Stereoacuity scores (seconds of arc) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

A logarithm base 10 transformation was used to convert stereoacuity scores to the log scale to calculate descriptive statistics (reported as log of seconds of arc, or log arcsec). The stereoacuity at near is reported at 3 years, as is the change in near stereoacuity from baseline to 3 years. Both were reported as log of seconds of arc, or log arcsec. For change in stereo, positive change indicates improvement in stereo.

Change in control is calculated as baseline level minus 3-year level, so positive change = improvement. Scale Range: 0 to 5. Improvement in control was defined as an improvement of 3 points based on the 3-point threshold for real change.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

Change in control is calculated as baseline level minus 3-year level, so positive change = improvement. Scale Range: 0 to 5. Improvement in control was defined as an improvement of 3 points based on the 3-point threshold for real change.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

Change in control is calculated as baseline level minus 3-year level, so positive change = improvement. Scale Range: 0 to 5. Improvement in control was defined as an improvement of 3 points based on the 3-point threshold for real change.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

Change in control is calculated as baseline level minus 3-year level, so positive change = improvement. Scale Range: 0 to 5. Improvement in control was defined as an improvement of 3 points based on the 3-point threshold for real change.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation. For change in PACT, positive change indicates improvement (i.e. decrease in angle over time).

log arcsec = logarithm of seconds of arc; Δ = prism diopter

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation. For change in PACT, positive change indicates improvement (i.e. decrease in angle over time). Improvement in PACT at distance was defined as a decrease of ≥8∆ because this amount exceed the repeatability coefficient of 7.2∆ for PACT angles larger than 20∆ at distance.

log arcsec = logarithm of seconds of arc; Δ = prism diopter

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation. For change in PACT, positive change indicates improvement (i.e. decrease in angle over time).

log arcsec = logarithm of seconds of arc; Δ = prism diopter

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation. For change in PACT, positive change indicates improvement (i.e. decrease in angle over time).

Improvement in PACT at near was defined as a decrease of ≥13∆ because this amount exceed the repeatability coefficient of 12.8∆ for PACT angles larger than 20∆ at near.

log arcsec = logarithm of seconds of arc; Δ = prism diopter

Patients randomized to the observation group will receive no treatment (other than refractive correction).

Occlusion treatment: Patients randomized to the occlusion treatment group will receive occlusion (patching) for 3 hours per day for at least 3 months. Choice of which eye to occlude, or whether to alternate daily, is at investigator's discretion.

Total of all reporting groups

This measure was used exclusively with the older cohort, no data reported on this characteristic for the younger cohort.

This measure was used exclusively with the older cohort, no data reported on this characteristic for the younger cohort.

This measure was used exclusively with the older cohort, no data reported on this characteristic for the younger cohort.

This measure was used exclusively with the older cohort, no data reported on this characteristic for the younger cohort.

Stereoacuity scores (seconds of arc) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

This measure was used exclusively with the older cohort, no data reported on this characteristic for the younger cohort.

Stereoacuity scores (seconds of arc, or arcsec) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

A logarithm base 10 transformation was used to convert stereoacuity scores to the log scale to calculate descriptive statistics (reported as log of seconds of arc, or log arcsec).

This measure was used exclusively with the older cohort, no data reported on this characteristic for the younger cohort.

Stereoacuity scores (seconds of arc, or arcsec) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

This measure was used exclusively with the older cohort, no data reported on this characteristic for the younger cohort.

Stereoacuity scores (seconds of arc, or arcsec) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

A logarithm base 10 transformation was used to convert stereoacuity scores to the log scale to calculate descriptive statistics (reported as log of seconds of arc, or log arcsec).

This measure was used exclusively with the older cohort, no data reported on this characteristic for the younger cohort.

AC/A= accommodative convergence to accommodation ratio

The Simultaneous Prism and Cover Test (SPCT) is performed by covering the fixating eye at the same time the prism is placed in front of the deviating eye. Prism diopters are the measure.

One participant was missing SPCT at near

The Simultaneous Prism and Cover Test (SPCT) is performed by covering the fixating eye at the same time the prism is placed in front of the deviating eye. Prism diopters are the measure.

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation.

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

The primary outcome measure for this study was whether the participant's condition had deteriorated within 3 years after randomization. Deterioration was defined as meeting one or both of the following criteria during any masked examination between 3 months and 3 years after randomization: 1) a constant exotropia (throughout the exam) of 10∆ or greater at distance and near by SPCT, confirmed by a retest, or 2) loss of near stereoacuity of 2 octaves (0.6 log arcsec) or more from the better of a test and retest of Preschool Randot stereoacuity at baseline, confirmed by a retest. In addition, participants were classified as deteriorated for the primary analysis if they started using non-randomized treatment (i.e., any treatment in the observation group; any treatment other than patching in the patching group) without first meeting one of the two protocol-specified deterioration criteria.

The clinical trial ended after 6 months, after which the purpose of the study was to observe the natural history of patients in the Observation arm. Because only half the occlusion group underwent further occlusion between 6 months and 3 years, the long-term occlusion group data was not felt to be of value, and there are no plans for its analysis.

The primary outcome measure was deterioration of the intermittent exotropia (IXT) within 6 months after randomization. Motor deterioration was defined as a constant exotropia of 10 D or more at distance and near by SPCT, confirmed by a retest, at either the 3- or 6-month visit.

Previously untreated children aged 12 to 35 months. Motor deterioration was measured by simultaneous prism and cover test.

The primary outcome measure was deterioration of the intermittent exotropia (IXT) within 6 months after randomization. Motor deterioration was defined as a constant exotropia of 10 D or more at distance and near by SPCT, confirmed by a retest, during any masked examination between 3 months and 3 years after randomization.

The younger cohort occlusion therapy group was not reported on. The clinical trial ended after 6 months, after which the purpose of the study was to observe the natural history of patients in the Observation arm. No data were collected from participants from 6 months to 3 years, and there are no plans for analysis.

Stereoacuity scores (seconds of arc) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

A logarithm base 10 transformation was used to convert stereoacuity scores to the log scale to calculate descriptive statistics (reported as log of seconds of arc, or log arcsec). The stereoacuity at distance is reported at 3 years, as is the change in distance stereoacuity from baseline to 3 years. Both were reported as log of seconds of arc, or log arcsec. For change in stereo, positive change indicates improvement in stereo.

Since only half the occlusion group underwent further occlusion between 6 months and 3 years, the long-term occlusion group data was not felt to be of value, and there are no plans for its analysis. For the observation group, the number reported is those who completed the 3-Year visit and had not been prescribed treatment anytime during the study.

Stereoacuity scores (seconds of arc) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

A logarithm base 10 transformation was used to convert stereoacuity scores to the log scale to calculate descriptive statistics (reported as log of seconds of arc, or log arcsec). The stereoacuity at near is reported at 3 years, as is the change in near stereoacuity from baseline to 3 years. Both were reported as log of seconds of arc, or log arcsec.

Outcome based on initial testing regardless of whether a retest was completed for suspected deterioration. Change is calculated as baseline level minus 6-month level. For change in stereo, positive change indicates improvement in stereo.

Stereoacuity data is missing for 2 observation group participants because it was not tested at the visit at which treatment was started in the absence of meeting deterioration criteria. The 6-month primary outcome visit was completed by 165 participants (90%) in the observation group, and by 159 participants (91%) in the patching group.

Stereoacuity scores (seconds of arc) were calculated based on the Randot Preschool stereoacuity test (scores: 800, 400, 200, 100, 60 and 40). Seconds of arc refers to the visual angle that is being measured in order to determine depth perception. Lower scores indicate better stereoacuity.

A logarithm base 10 transformation was used to convert stereoacuity scores to the log scale to calculate descriptive statistics (reported as log of seconds of arc, or log arcsec). The stereoacuity at near is reported at 3 years, as is the change in near stereoacuity from baseline to 3 years. Both were reported as log of seconds of arc, or log arcsec. For change in stereo, positive change indicates improvement in stereo.

The older cohort occlusion therapy group was not reported on. The clinical trial ended after 6 months, after which the purpose of the study was to observe the natural history of patients in the Observation arm. No data were collected from participants from 6 months to 3 years, and there are no plans for analysis.

Change in control is calculated as baseline level minus 3-year level, so positive change = improvement. Scale Range: 0 to 5. Improvement in control was defined as an improvement of 3 points based on the 3-point threshold for real change.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

For the Older Cohort, the 6-month primary outcome visit was completed by 165 participants (90%) in the observation group, and by 159 participants (91%) in the patching group.

Change in control is calculated as baseline level minus 3-year level, so positive change = improvement. Scale Range: 0 to 5. Improvement in control was defined as an improvement of 3 points based on the 3-point threshold for real change.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

Since only half the occlusion group underwent further occlusion between 6 months and 3 years, the long-term occlusion group data was not felt to be of value, and there are no plans for its analysis. For the observation groups, the number reported is those who completed the 3-Year visit and had not been prescribed treatment anytime during the study.

Change in control is calculated as baseline level minus 3-year level, so positive change = improvement. Scale Range: 0 to 5. Improvement in control was defined as an improvement of 3 points based on the 3-point threshold for real change.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

For the Older Cohort, the 6-month primary outcome visit was completed by 165 participants (90%) in the observation group, and by 159 participants (91%) in the patching group.

Change in control is calculated as baseline level minus 3-year level, so positive change = improvement. Scale Range: 0 to 5. Improvement in control was defined as an improvement of 3 points based on the 3-point threshold for real change.

Numeric values for exotropia control were assigned so that the following categories were created:

Not applicable (no exodeviation) 0: No exotropia unless dissociated, recovers <1 secs (phoria)

1. No exotropia unless dissociated, recovers 1-5 secs
2. No exotropia unless dissociated, recovers >5 secs
3. Exotropia <50% of 30-second observation
4. Exotropia >50% of 30-second observation
5. Constant exotropia

Lower scores indicate better control.

Since only half the occlusion group underwent further occlusion between 6 months and 3 years, the long-term occlusion group data was not felt to be of value, and there are no plans for its analysis. For the observation groups, the number reported is those who completed the 3-Year visit and had not been prescribed treatment anytime during the study.

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation. For change in PACT, positive change indicates improvement (i.e. decrease in angle over time).

log arcsec = logarithm of seconds of arc; Δ = prism diopter

For the Older Cohort, the 6-month primary outcome visit was completed by 165 participants (90%) in the observation group, and by 159 participants (91%) in the patching group.

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation. For change in PACT, positive change indicates improvement (i.e. decrease in angle over time). Improvement in PACT at distance was defined as a decrease of ≥8∆ because this amount exceed the repeatability coefficient of 7.2∆ for PACT angles larger than 20∆ at distance.

log arcsec = logarithm of seconds of arc; Δ = prism diopter

Since only half the occlusion group underwent further occlusion between 6 months and 3 years, the long-term occlusion group data was not felt to be of value, and there are no plans for its analysis. For the observation groups, the number reported is those who completed the 3-Year visit and had not been prescribed treatment anytime during the study.

The prism and alternate cover test (PACT) is used to measure the angle of strabismus, or deviation, in prism diopters. This is measured separately at distance and at near. Smaller numbers are better because they indicate a smaller angle of deviation. For change in PACT, positive change indicates improvement (i.e. decrease in angle over time).

log arcsec = logarithm of seconds of arc; Δ = prism diopter

For the Older Cohort, the 6-month primary outcome visit was completed by 165 participants (90%) in the observation group, and by 159 participants (91%) in the patching group.