Base-in Prism Spectacles for Intermittent Exotropia

The primary analysis will be an intent-to-treat comparison of mean 8-week control of the distance exodeviation (average of 3 measurements) between treatment groups using an analysis of covariance (ANCOVA) model, which adjusts for baseline distance control. Distance control scores range from 0 to 5 with higher scores indicating a worse outcome.

The secondary analysis will calculate the percentage of participants with a "treatment response," defined as ≥1 point improvement in control of their distance exodeviation (average of 3 measurements) between baseline and the 8-week outcome exam.

The proportion of participants with no spontaneous tropia at 8 weeks will be compared between treatment groups using a two-sided Barnard's test with alpha of 0.05, with calculation of a two-sided 95% confidence interval on the difference in proportions.

No spontaneous tropia at the 8-week primary outcome exam is defined as a score of ≤2 (0, 1, or 2) on all three assessments of control at distance and at near.

Control of the exodeviation was measured at distance using the IXT Office Control Score, (Mohney, 2006) which ranges from 0 (phoria) to 5 (constant exotropia). Control levels 3-5 were assigned based on the duration of manifest exotropia during a 30-second period before any dissociation. If no exotropia was observed, control levels 0-2 were assigned based on the longest time to reestablishing fusion after 3 consecutive 10-second periods of dissociation. Control was measured at the beginning, middle, and end (3 tests) of a 20- to 40-minute office examination, and the mean was used. The change in distance control from baseline to 8 weeks will be calculated. A negative value indicates improvement.

Near control will be evaluated similarly to the primary outcome and outcome measures 2-4. Near control scores range from 0 to 5 with higher scores indicating a worse outcome.

The measure of ocular alignment at distance by PACT will be summarized at 8 weeks for each treatment group. A higher deviation is worse.

The measure of ocular alignment at near by PACT will be summarized at 8 weeks for each treatment group. A higher deviation is worse.

Randot® Preschool Stereoacuity test (Stereo Optical Co., Inc., Chicago, IL). For analysis, stereoacuity was converted from seconds of arc scores to log arcsec values (in parentheses) as follows: 40 (1.60), 60 (1.78), 100 (2.00), 200 (2.30), 400 (2.60), 800 (2.90); participants with no detectable (nil) stereoacuity were assigned the value of 1600 (3.20). The measure of Randot Preschool Stereoacuity at near will be summarized at 8 weeks for each treatment group. A lower score is better.

Parents will be asked to complete a compliance calendar by recording the percentage of time their child has worn the study-prescribed spectacle correction each day. Proportion of time worn each day will be described as excellent (76% to 100%), good (51% to 75%), fair (26% to 50%), poor (1 to 25%), or none (0%). Based on review of the calendars and discussion with parents at the 8-week outcome exam, the investigator will record the total proportion of time worn as excellent (76% to 100%), good (51% to 75%), fair (26% to 50%), poor (1 to 25%), or none (0%: did not fill prescription or never picked up spectacles).

The distribution of compliance will be assessed for each treatment group at the outcome exam.

Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia will be summarized at the 8-week outcome exam using a symptom survey that is administered to the child. Response options are based on frequency of observations: never, sometimes, and always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent.

Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent.

Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent.

Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent.

Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent.

Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent.

Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Adverse symptoms of intermittent exotropia and spectacle wear will be summarized at the 8-week outcome exam using a symptom survey that is administered to the parent.

Response options are based on frequency of observations: never, almost never, sometimes, often, and almost always. The distribution of scores on each survey item will be tabulated by treatment group after 8-weeks.

Distance visual acuity will be assessed at the 8-week outcome exam. Any optotype method can be used for testing. The distribution of distance visual acuity Snellen Equivalents will be tabulated for each treatment group. A lower Snellen Equivalent is best.

As an exploratory analysis, the distribution of fusional convergence amplitude (break point, blur point, and recovery) at 8 weeks will be summarized for each treatment group. Fusional amplitudes are a measure of how well a participant can converge their eyes using fusional vergence. It is measured by increasing base-out prism to the point that the participant is no longer able to control the deviation. The total amount of fusion is the magnitude of the base-out prism the participant was able to overcome plus the magnitude of the deviation. A higher number of prism diopters for break point is better than a lower number. A lower number for recovery point is better than a higher number.

The suppression assessment is a standardized method of assessing the depth of suppression experienced while the participant is tropic (NOT aligned). Scoring is reported on an ordinal scale from 0 (no suppression) to 3 (dense suppression). "Missing" refers to cases in which participants were unable to understand the test and/or gave unreliable responses. As an exploratory analysis, the distribution of suppression level (none, mild, moderate, severe, missing) will be tabulated after 8 weeks by treatment group.

As an exploratory analysis, the distribution of fusional convergence amplitude (break point, blur point, and recovery) at 8 weeks will be summarized for each treatment group. Fusional amplitudes are a measure of how well a participant can converge their eyes using fusional vergence. It is measured by increasing base-out prism to the point that the participant is no longer able to control the deviation. The total amount of fusion is the magnitude of the base-out prism the participant was able to overcome plus the magnitude of the deviation. A higher number of prism diopters for break point is better than a lower number. A lower number for recovery is better than a higher number.