Augmenting Atropine Treatment for Amblyopia in Children 3 to < 8 Years Old: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Augmenting Atropine Treatment for Amblyopia in Children 3 to < 8 Years Old (NCT00944710), a randomized phase 3 study. The primary outcome is Distribution of 10-week Amblyopic-Eye Visual Acuity.

2. Clinical Question

The question is specifically about adding a plano lens after an initial course of weekend atropine had reached a point of no further improvement, rather than comparing initial atropine treatment with no treatment. The run-in therefore defines the clinical context for the randomized comparison: participants had received initial treatment, had stabilized, and remained eligible for randomization.

The registry record describes the primary outcome as a distribution of visual-acuity scores, not as one threshold or a single average. That distinction matters statistically. A distribution can show how observations are spread across outcome categories, while a single summary could conceal changes in different parts of that distribution. The record does not report a numerical primary treatment contrast, confidence interval, or p-value, so the magnitude and precision of any difference between groups are not reported in the registry record.

3. Trial Design

This was a Phase 3, randomized, parallel-group trial. The registry record lists enrollment as 73. Children entered a run-in phase with weekend atropine, and eligible participants were then randomized to weekend atropine with a plano lens over the sound eye or weekend atropine alone. The stated trial objective was to evaluate whether adding the plano lens improved visual acuity when amblyopia remained after visual acuity had stabilized with the initial treatment.

The registry describes masking as none. Separately, the primary-outcome description says that masked 10-week amblyopic-eye visual-acuity scores were tabulated. The record does not explain the masking procedures or how those two descriptions relate, so the details of masking are not reported in the registry record. Randomization can support a fair comparison of assigned groups, but it does not by itself establish that participants, clinicians, or outcome assessors were unaware of assignment.

The primary outcome used visual-acuity examinations completed 8 to 15 weeks after randomization, inclusive, as the registry’s 10-week assessment window. No imputation was used for missing primary-outcome data. The primary analysis followed the intent-to-treat principle: randomized participants were included regardless of whether they received the assigned treatment or deviated from protocol. Participants later found ineligible after review of enrollment data were also included in that analysis.

The registry record lists secondary outcomes involving visual-acuity thresholds and improvement, spectacle and atropine compliance, and interocular difference. It lists 26 outcome measures and 5 analyses. The record does not report the detailed randomization procedure, allocation concealment, sample-size justification, or a full statistical analysis plan. These details should not be inferred from the randomized, parallel-group design alone.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: Prior to being considered for the randomized trial, participants who had not completed at least 12 weeks of atropine were enrolled into a run-in phase and treated with weekend atropine 1% ophthalmic solution and spectacles based upon a recent cycloplegic refraction, with follow up every 6 weeks until no improvement

10-week Primary Outcome

12-week Visit (Off-treatment)

Additional Post 10-week Primary Outcome

Analysis population for the primary outcome, as defined in the registry: The primary outcome analysis followed the intent-to-treat principle and included data from 10-week visual acuity exams completed between 8 and 15 weeks (inclusive) with no imputation for missing data.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Distribution of 10-week Amblyopic-Eye Visual Acuity, measured over 10 weeks after randomization.

The primary endpoint is the distribution of amblyopic-eye visual-acuity scores at 10 weeks after randomization. It concerns visual acuity in the amblyopic eye, rather than a compliance measure or an adverse-event count. The registry says scores from qualifying examinations completed between 8 and 15 weeks, inclusive, were tabulated for both treatment groups, with no imputation for missing values.

In general, a distributional endpoint retains information about how outcomes are spread across participants and categories. This can be useful when the outcome is recorded on an ordered scale: an analysis can describe the pattern across the scale rather than reducing it to one cutoff. The registry record does not provide the category counts or the planned inferential method for comparing the distributions, so the specific statistical interpretation of each category cannot be assessed from the record alone.

A visual-acuity endpoint is relevant to the stated trial objective because the intervention was intended to be evaluated in relation to amblyopic-eye visual acuity. However, the endpoint definition does not itself establish a treatment benefit. To judge the comparison, readers would need the group-specific outcome distribution and an estimate of the contrast, with its uncertainty. Those primary comparison results are not reported in the registry record as a single estimate, and no numerical primary effect or confidence interval is reported in the registry record for this analysis.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does randomization contribute?

In general, randomization assigns participants to treatment groups by chance. Its purpose is to reduce systematic differences between groups at the time of assignment, including differences that might otherwise influence the outcome. It does not guarantee that the groups are identical in every characteristic, and it does not remove uncertainty from the observed comparison. In this trial, the randomized groups were weekend atropine with a plano lens and weekend atropine alone. The record does not report the sequence-generation or allocation-concealment methods, so those operational details are not reported in the registry record.

What is a parallel-group comparison?

In a parallel-group design, participants are assigned to one study regimen and the groups are compared over the relevant follow-up. Here, the assigned regimens differed by the addition of a plano lens to weekend atropine 1%. The randomized comparison followed a run-in phase: children first received weekend atropine until visual acuity no longer improved, then eligible participants were randomized if amblyopia remained. The estimate from such a comparison would address the added lens in that treatment context; it would not directly answer what happens when the two regimens are used as initial treatment.

What does the intent-to-treat principle mean?

In general, an intent-to-treat analysis keeps participants in the groups to which they were randomized, regardless of whether they received the assigned treatment or followed the protocol. This preserves the comparison created by randomization and estimates the effect of assignment under the trial’s conditions. The registry explicitly says that randomized participants were included even if assigned treatment was not received or treatment deviated from protocol. It also says that participants later judged ineligible after enrollment-data review remained in the primary analysis. The record does not explain how any such deviations or later eligibility findings were handled in analyses other than the primary analysis.

What does the outcome window mean?

The primary outcome is described as a 10-week assessment, using visual-acuity exams completed from 8 to 15 weeks after randomization, inclusive. In general, a window allows observations made within a prespecified range to contribute to a visit-based endpoint when assessments do not all occur on exactly the same day. Here, the registry identifies the window but does not report the distribution of actual examination times or explain why this specific window was selected. It also states that missing primary visual-acuity data were not imputed. Thus, the record describes use of available qualifying examinations rather than an imputed value for a missing examination.

How should a distributional endpoint be read?

A distributional outcome describes how observations fall across the outcome scale or categories. In general, this can preserve more detail than a single average or a binary threshold, especially when the outcome has ordered levels. A comparison may consider whether the overall patterns differ, but the specific method and assumptions matter. The registry names the primary endpoint as the distribution of 10-week amblyopic-eye visual acuity and states that scores were tabulated for both groups. It does not report category frequencies, a test statistic, an effect estimate, or the statistical procedure used to compare the distributions. Consequently, the exact inferential method cannot be reconstructed from the record.

Why does uncertainty matter?

In general, a confidence interval communicates uncertainty around an estimated treatment contrast. It is not a guarantee that the true effect lies within the interval, and it should be considered alongside the estimate and the outcome’s meaning. A p-value addresses compatibility of the observed data with a specified null model and assumptions; it does not state the probability that a treatment works. The registry record does not report a primary confidence interval or p-value in the registry record for this analysis. The result therefore cannot be characterized in terms of statistical precision or a conventional significance test.

What do the planning assumptions say?

The sample-size planning illustration is described as based on the observed effect rather than the trial’s own design. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. In general, such illustrations show how a planning calculation can vary with the effect size one chooses to target. They are not observed power, and they do not establish the trial’s original design rationale. The record does not report the trial’s own sample-size justification. No numerical planning result is reported in the registry record for this analysis, so none can be interpreted.

What remains unknown about the analysis?

The registry record does not report the detailed statistical model, covariate adjustment, handling of multiplicity, or a prespecified hierarchy among outcomes. These details should not be inferred from the fact that the record lists multiple analyses and outcome measures. In general, methods should be judged in relation to the endpoint, the design, and the analysis plan established before examining outcomes. Without the plan and the numerical primary results, the robustness of the reported analysis cannot be assessed from the registry record alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 26 outcome measures and 5 analyses, including a primary distributional visual-acuity endpoint and secondary outcomes involving visual-acuity thresholds, improvement, compliance, and interocular difference. When several outcomes or comparisons are examined, the chance of at least one apparently notable result can increase if each is assessed without accounting for the multiplicity. In general, multiplicity approaches can define a primary outcome, adjust inference across a family of tests, or use a prespecified hierarchy. The registry record does not report a multiplicity procedure or explain how the listed analyses relate to one another.

The primary analysis followed the intent-to-treat principle. It included randomized participants regardless of treatment receipt or protocol deviation, and it included participants subsequently judged ineligible after enrollment data review. The primary outcome used qualifying visual-acuity exams completed 8 to 15 weeks after randomization, inclusive. No imputation was used for missing primary outcome values.

In general, not imputing missing values means that missing outcomes are not replaced by estimates under an imputation model. The resulting analysis may depend on which participants have an observed qualifying exam; interpretation therefore benefits from knowing the amount and pattern of missingness and whether missingness differs between groups. Those details are not reported in the registry record. The record also does not describe sensitivity analyses for missing data or provide enough information to assess the consequences of missing observations.

The stated analysis population and missing-data rule are useful, but do not settle questions about the statistical plan. The registry record does not report a detailed analysis plan, the handling of multiplicity, or an explanation of how non-primary analyses were selected or interpreted.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse events for the control and intensified-treatment groups. In control, 0 serious events were reported among 40 participants at risk; in intensified treatment, 0 were reported among 33 participants at risk. The registry also reports 5 other adverse events among 40 at risk in control and 9 among 33 at risk in intensified treatment. These are group-specific counts and denominators as recorded, not a formal comparison of risk.

In general, a count of zero observed events does not establish that an event is impossible or that the risk is absent. Safety interpretation depends on the event definitions, follow-up, ascertainment, and the amount of information available. The record does not report the serious-event terms, and it does not provide event descriptions for the other adverse events in the registry record for this analysis. Death counts are not reported in the registry record.

The numbers should therefore be read descriptively. They do not provide a comparative estimate with a confidence interval, and they do not address the primary visual-acuity endpoint. No conclusion about relative safety should be drawn from these counts alone.

12. What the Result Does, and Does Not, Mean

The trial addresses a specific treatment question: whether adding a plano lens over the sound eye to weekend atropine 1% changes the distribution of amblyopic-eye visual acuity at the 10-week assessment, among eligible children whose acuity had stabilized with initial weekend atropine but who still had amblyopia. Its randomized parallel-group design and intent-to-treat primary analysis identify how the comparison was intended to be made.

The registry record does not report the primary group-specific distribution or a numerical treatment contrast in the registry record for this analysis. It is therefore not possible to state whether the outcome distribution favored either group, how large any difference was, or how precisely it was estimated. The trial objective is not a result, and the descriptive adverse-event figures do not answer the primary question.

In general, evidence from a trial applies most directly to the population, intervention, comparator, and follow-up actually studied. This trial’s stated population was children ages 3 to <8 years who entered a run-in and were eligible for randomization after stabilization while amblyopia remained. The comparison was not an unrestricted evaluation of initial treatment, nor does the record establish effects outside the described context.

The record also does not report enough information to judge the magnitude or uncertainty of secondary outcomes, missing-data sensitivity, multiplicity handling, or detailed analysis choices. The practical meaning of any treatment contrast would depend on the observed outcome distribution and its uncertainty, neither of which is available. Accordingly, the registry description supports an account of the question and design, but not a claim that either regimen produced a particular visual-acuity result.

13. Why This Trial Matters Statistically

This trial is statistically notable for asking an add-on question after an initial treatment run-in. The randomized comparison is between weekend atropine 1% alone and the same regimen with a plano lens over the sound eye, among children who had stabilized but still had amblyopia. That structure makes the target contrast specific: it concerns the added lens in the setting described by the registry, rather than the effect of starting atropine or the effect of treatment in a different population.

The primary endpoint is a distribution of visual-acuity scores rather than a single threshold. In general, this approach can retain information across outcome levels and avoids making the entire primary question depend on one cutoff. It also requires clear reporting of categories, group patterns, and the method used to compare them. The registry record identifies the endpoint but does not report those numerical primary results or the detailed comparison method in the registry record for this analysis.

The record’s intent-to-treat description is also important. Keeping randomized participants in their assigned groups, including those who did not receive treatment as assigned or were later judged ineligible, preserves the assignment-based comparison as defined by the registry. At the same time, the missing-data rule—no imputation for missing primary values—means that the observed endpoint data and the extent of missingness are relevant to interpretation. The record does not report the missingness details.

Finally, the trial illustrates why a design description and a result must be distinguished. Randomization, a defined follow-up window, and a stated primary endpoint describe how a question was approached; they do not establish the direction, size, or precision of the answer. Those features make the registry record useful for understanding the intended comparison, while the absence of reported primary estimates limits statistical conclusions.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record leaves several trial-specific uncertainties. It describes the trial as unmasked, while the primary-outcome description calls the 10-week visual-acuity scores masked. It does not explain who was masked, how masking was implemented, or how the descriptions fit together. The consequences for outcome assessment therefore cannot be evaluated from the registry record.

The primary analysis used examinations in the 8-to-15-week window and did not impute missing data, but the record does not report the amount or pattern of missing visual-acuity data by group. Without that information, the influence of missing outcomes on the observed distribution cannot be assessed. The record also does not report a sensitivity analysis for missing data.

The primary endpoint is distributional, but the category counts and comparison method are not reported in the registry record for this analysis. No primary effect estimate, confidence interval, or p-value is available. As a result, the direction, magnitude, and precision of the treatment contrast cannot be assessed. The record lists multiple outcomes and analyses but does not report how multiplicity was handled or how the analysis plan prioritized them.

Other design details—including the randomization procedure, allocation concealment, and the trial’s own sample-size justification—are not reported in the registry record. The planning illustration is explicitly described as based on the observed effect rather than the trial’s original design. These omissions limit evaluation of design choices and analysis robustness; they do not establish that a particular method was or was not used.

Safety reporting is also limited in the registry entries: serious-event terms are absent, descriptions for other events are not given, and death counts are not reported in the registry record. These limitations call for restraint in interpreting the descriptive counts and do not resolve the primary visual-acuity question.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Augmenting Atropine Treatment for Amblyopia in Children 3 to < 8 Years Old — NCT00944710.
• Registry record last updated 2019-03-06; status last verified 2019-02.
• Results first posted 2014-10-24.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry record describes a completed Phase 3 randomized parallel-group trial with enrollment listed as 73. Children ages 3 to <8 years with amblyopia entered a weekend-atropine run-in; eligible children with stabilized visual acuity and remaining amblyopia were randomized to weekend atropine 1% with a plano lens over the sound eye or weekend atropine 1% alone.

The primary endpoint was the distribution of amblyopic-eye visual acuity 10 weeks after randomization, using exams completed 8 to 15 weeks after randomization, inclusive. The primary analysis followed intent-to-treat and used no imputation for missing primary outcome values. The registry lists secondary outcomes related to visual acuity, compliance, and interocular difference.

The primary treatment-group results and their statistical uncertainty are not reported in the registry record for this analysis. Serious adverse-event counts were 0 among 40 at risk in control and 0 among 33 at risk in intensified treatment; other-event counts were 5 and 9, respectively. Death counts are not reported in the registry record.