A comparison of mean control of the distance exodeviation (average of 3 measurements over the exam) between the 2.50 diopters (D) overminus group and the non-overminus group (spectacles without overminus or no spectacles) at 12 months. The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

A comparison of mean control of the distance exodeviation (average of 3 measurements over the exam) between the 2.50D overminus group and the non-overminus group (spectacles without overminus or no spectacles) at 18 months (after treatment discontinuation). The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

The number of subjects with no spontaneous tropia at 12 months and at 18 months will be compared between treatment groups.

The proportion of subjects with no spontaneous tropia at 12 months and at 18 months will be compared between treatment groups.

The proportion of subjects with ≥1 point improvement in distance control between baseline and 12 months will be compared between treatment groups. The proportion of subjects with ≥2 points improvement in distance control will be similarly compared between treatment groups. The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

The proportion of subjects with ≥1 point improvement in distance control between baseline and 18 months will be compared between treatment groups. The proportion of subjects with ≥2 points improvement in distance control will be similarly compared between treatment groups. The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

The cumulative proportion of subjects who meet deterioration criteria by the time point will be estimated for each treatment group.

Participants who meet either of the following at any visit by a specific timepoint (e.g., 12 months, 18 months) will be considered to have met deterioration criteria by that timepoint.

• Motor deterioration: Control of the exodeviation measures 5 (constant exotropia) on all three assessments at distance and near. The exodeviation does not need to be constant throughout the entire exam provided that it is constant during all three assessments of control.
• Stereoacuity deterioration: Drop in near stereoacuity of at least 2 octaves from enrollment stereoacuity, or to nil, confirmed by a retest by a Masked Examiner on a subsequent day.

Note: participants with nil stereoacuity at enrollment will not be able to deteriorate with respect to a drop in near stereoacuity.

The cumulative proportion of subjects who meet deterioration criteria by the time point will be estimated for each treatment group.

Participants who meet either of the following at any visit by a specific timepoint (e.g., 12 months, 18 months) will be considered to have met deterioration criteria by that timepoint.

• Motor deterioration: Control of the exodeviation measures 5 (constant exotropia) on all three assessments at distance and near. The exodeviation does not need to be constant throughout the entire exam provided that it is constant during all three assessments of control.
• Stereoacuity deterioration: Drop in near stereoacuity of at least 2 octaves from enrollment stereoacuity, or to nil, confirmed by a retest by a Masked Examiner on a subsequent day.

Note: participants with nil stereoacuity at enrollment will not be able to deteriorate with respect to a drop in near stereoacuity.

Mean control of the near exodeviation (average of 3 measurements over the exam). The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

Mean control of the near exodeviation (average of 3 measurements over the exam). The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

For each timepoint, the change in near control since baseline will be reported. The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

For each timepoint, the change in near control since baseline will be reported. The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

The magnitude of the deviation by Prism Alternate Cover Test (PACT) will be compared between treatment groups.

The magnitude of the deviation by Prism Alternate Cover Test (PACT) will be compared between treatment groups.

A comparison of near stereoacuity will be assessed using the Randot Preschool stereotest at near (performed at 40 cm) between treatment groups.

A comparison of near stereoacuity will be assessed using the Randot Preschool stereotest at near (performed at 40 cm) between treatment groups.

Compliance with spectacle wear will be assessed at the 12-month and 18-month outcome exam. Parents will give an estimate of the proportion of the time their children wore their spectacles. Proportion of time worn will be described as excellent (76% to 100%), good (51% to 75%), fair (26% to 50%), or poor (≤ 25%). The distribution of compliance will be assessed for each treatment group at the outcome exam.

Compliance with spectacle wear will be assessed at the 12-month and 18-month outcome exam. Parents will give an estimate of the proportion of the time their children wore their spectacles. Proportion of time worn will be described as excellent (76% to 100%), good (51% to 75%), fair (26% to 50%), or poor (≤ 25%). The distribution of compliance will be assessed for each treatment group at the outcome exam.

A brief survey of symptoms that may be associated with overminus such as headaches, eye strain, and problems with spectacle wear will be administered to the parents of the subjects. Parents are asked to respond to the survey questions based on their observations of their child in the past 2 weeks. Response options are based on frequency of observations; never, rarely, sometimes, often, always, and not applicable.

When number analyzed differs from full population size, it indicates that those children were not wearing spectacles, and therefore could not answer the spectacle related questions.

A brief survey of symptoms that may be associated with overminus such as headaches, eye strain, and problems with spectacle wear will be administered to the parents of the subjects. Parents are asked to respond to the survey questions based on their observations of their child in the past 2 weeks. Response options are based on frequency of observations; never, rarely, sometimes, often, always, and not applicable.

When number analyzed differs from full population size, it indicates that those children were not wearing spectacles, and therefore could not answer the spectacle related questions.

NIH-required analysis. Primary outcome measure (stratified by sex):

A comparison of mean control of the distance exodeviation (average of 3 measurements over the exam) between the 2.50 diopters (D) overminus group and the non-overminus group (spectacles without overminus or no spectacles) at 12 months. The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

Data were stratified by sex

NIH-required analysis. Primary outcome measure (stratified by race):

A comparison of mean control of the distance exodeviation (average of 3 measurements over the exam) between the 2.50 diopters (D) overminus group and the non-overminus group (spectacles without overminus or no spectacles) at 12 months. The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

Data were stratified by race

NIH-required analysis. Primary outcome measure (stratified by ethnicity):

A comparison of mean control of the distance exodeviation (average of 3 measurements over the exam) between the 2.50 diopters (D) overminus group and the non-overminus group (spectacles without overminus or no spectacles) at 12 months. The Office Control Score provides a rating of exodeviation control on a 0 to 5 scale, in subjects with intermittent exotropia. Scores 3 to 5 reflect the proportion of time a spontaneous manifest exotropia is present during 30 seconds of observation (<50% score 3; >50% score 4; 100% score 5). If no spontaneous manifest exotropia is observed, scores 0 to 2 reflect the longest time to regain fusion after three, 10-second dissociations (>5 seconds score 2; 1-5 seconds score 1; <1 second score 0).

Data were stratified by ethnicity