Levodopa for the Treatment of Residual Amblyopia: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Levodopa for the Treatment of Residual Amblyopia (NCT01190813), a randomized phase 3 study. The primary outcome is Distribution of Amblyopic Eye Visual Acuity Change From Baseline.

2. Clinical Question

This framing separates the treatment contrast from the way the outcome was measured. Random assignment supports a group comparison, while the reported baseline-adjusted analysis was intended to account for starting visual acuity. The available record does not specify the randomization procedure, concealment method, or any further eligibility criteria beyond those in the study summary. Details such as the patching regimen, adherence, and how treatment adherence was handled analytically are not reported in the registry record.

3. Trial Design

The study is identified as a Phase 3 randomized trial with a parallel-group design and quadruple masking. The registry lists an enrollment of 139 and a completed status. The recorded study start is 2010-09 and the primary completion is 2014-01. The sponsor is Jaeb Center for Health Research.

The active group received levodopa/carbidopa with patching; the comparator group received oral placebo with patching. The listed doses were levodopa 0.76 mg/kg with carbidopa 0.17 mg/kg tid and oral placebo tid. The record does not define which roles were included in quadruple masking or explain how masking was maintained. It also does not report the randomization sequence method, allocation concealment, or whether allocation was stratified.

The planned primary assessment was at 18 weeks after enrollment. The registry says study medicine began a rapid taper at week 16 before that visit. It describes measurement using the Electronic Early Treatment of Diabetic Retinopathy Study visual-acuity protocol, with a study-certified tester and the right eye measured first. Five letters is equivalent to one logMAR line.

Secondary outcomes listed in the record include visual-acuity comparisons at several follow-up times, the distribution and mean of acuity at 18 weeks, and amblyopia resolution at 4 weeks. The record lists 43 outcome measures and 9 analyses. It does not provide a full account of how these measures and analyses were organized, prioritized, or handled statistically. In particular, the registry record does not report a sample-size justification or the trial's complete statistical analysis plan.

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.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The ITT principle was followed. For subjects with no visit in the +/- 1 wk window for the 18-wk visit, data from a visit 14-27 wks after randomization were used, if available. Multiple imputation by the Monte Carlo Markov Chain method was used for missing 18-wk VA outcomes based on tx group, baseline VA, \& VA scores from completed follow-up visits.

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 Amblyopic Eye Visual Acuity Change From Baseline, measured over 18 weeks after enrollment.

The primary endpoint is described as the distribution of change from baseline in amblyopic-eye visual acuity, assessed at the 18-week primary outcome visit. The detailed description also states that the primary analytic approach was a comparison of mean amblyopic-eye visual acuity between treatment groups, adjusted for baseline acuity. These descriptions indicate an outcome centered on visual acuity while presenting both a distribution-oriented title and a mean-based analysis description. The registry record does not reconcile that wording or provide the numerical group comparison.

Visual acuity was measured with the Electronic Early Treatment of Diabetic Retinopathy Study protocol by a study-certified tester. The record states that five letters is equivalent to one logMAR line. A letter score gives a measured scale on which changes in visual acuity can be compared between groups, while baseline adjustment accounts statistically for starting acuity when estimating the follow-up group contrast.

An endpoint measured at a specified follow-up time makes the comparison interpretable in relation to the study schedule. In this trial, the 18-week visit occurred after the recorded rapid taper began at week 16. That timing is part of the endpoint definition; it does not by itself establish the effect of treatment or explain how long any effect might persist. The numerical estimate, its confidence interval, and the primary hypothesis test are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does randomization contribute? Randomization assigns participants to treatment groups using a chance-based process. In general, this helps make groups comparable at the start with respect to measured and unmeasured characteristics, though chance imbalances can remain. This trial is recorded as randomized, but the sequence-generation and allocation-concealment methods are not reported in the registry record. The label alone does not describe how assignment was carried out.

What does masking mean? The registry describes the trial as quadruple-masked. In general, masking is intended to reduce the influence of knowledge about assigned treatment on participant experience, clinical care, outcome assessment, or analysis. The record does not identify the roles included in the masking label, or explain how masking was maintained or assessed. The classification therefore describes the recorded design without giving enough detail to evaluate its implementation.

Why adjust for baseline acuity? The primary analysis is described as comparing mean amblyopic-eye acuity at follow-up while adjusting for baseline acuity. In general, adjustment uses the starting measurement when estimating a follow-up group contrast. This can account for differences in baseline values and may improve precision when baseline and follow-up measurements are related. The registry record does not name the specific statistical model, state which additional variables were included, or provide the adjusted estimate and its uncertainty.

How should the endpoint scale be understood? Visual acuity was measured using the Electronic Early Treatment of Diabetic Retinopathy Study protocol. The record states that five letters is equivalent to one logMAR line. This is a measurement interpretation, not a treatment-effect estimate. A group mean can describe the average score, while a distribution can show how scores vary across participants. The registry's primary-outcome title refers to a distribution of change, but its description refers to an adjusted comparison of mean acuity. The relationship between these summaries is not reported in the registry record.

What does a confidence interval tell a reader? In general, a confidence interval gives a range of values compatible with the data and the statistical procedure used, subject to the model's assumptions. Its width communicates precision: a wider interval indicates more uncertainty about the estimate. Statistical compatibility is not the same as clinical importance, and an interval does not remove uncertainty about bias or measurement quality. The primary estimate and confidence interval are not reported in the registry record, so neither the magnitude nor precision of the primary contrast can be evaluated.

Why can outcome distributions matter? A mean can conceal variation in responses or differences in the shape of the outcome distribution. Examining distributions can help show whether results are concentrated or dispersed and whether a small number of unusual observations influence an average. In general, the appropriate summary depends on the outcome scale and the scientific question. The registry record does not provide the primary category-level results, a distributional analysis method, or a clear account of how the distribution wording relates to the mean-based primary analytic description.

What is over-dispersion? In general, over-dispersion occurs when observed variability is greater than a statistical model expects. If ignored in a setting where it applies, estimated uncertainty can be too small and inference too confident. Whether over-dispersion is relevant depends on the outcome and analysis model. The registry record does not identify a model for counts or report an over-dispersion assessment; it would not be appropriate to assume one was needed or used for the visual-acuity endpoint.

What can safety counts establish? The registry lists affected-participant counts for serious and other adverse events by group. Counts describe how many participants were recorded in each category, but they do not on their own describe timing, recurrence, severity, or the statistical uncertainty of a between-group comparison. A safety interpretation also depends on the event definitions and the way events were collected and analyzed. Those details and a comparative safety analysis are not reported in the registry record.

These general statistical principles clarify what the design and endpoint descriptions mean, but they cannot replace missing trial-specific estimates. The record does not report the primary comparison, its uncertainty, the detailed model specification, or the complete statistical analysis plan.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 43 outcome measures and 9 analyses, alongside secondary outcomes covering visual-acuity measures at multiple follow-up times and amblyopia resolution. When many outcomes, time points, or analyses are considered, the chance of at least one apparently notable finding can increase. In general, multiplicity procedures may adjust interpretation or testing to account for a set of comparisons. The registry record does not report whether multiplicity was addressed, which outcomes were included in any adjustment, or how the primary outcome was distinguished statistically from secondary analyses. The number of listed outcomes alone does not establish which comparisons were prespecified or tested.

The record says the ITT principle was followed. For participants without a visit in the +/- 1 wk window for the 18-week visit, data from a visit 14-27 wks after randomization were used if available. It also says multiple imputation by the Monte Carlo Markov Chain method was used for missing 18-week visual-acuity outcomes. The description of the variables used in imputation is truncated after referring to treatment group and baseline information, so the full imputation model is not reported in the registry record.

In general, multiple imputation represents missing outcomes using a model and combines analyses across imputed datasets to reflect uncertainty from missingness. Its validity depends on assumptions about the missing-data process and on the model being appropriate. The record does not report the number of missing primary outcomes, the assumptions underlying imputation, diagnostics, or sensitivity analyses for departures from those assumptions. The ITT statement describes the analysis population principle, but does not by itself resolve uncertainty due to missing data or supply the primary result.

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 two treatment groups as participant counts. The levodopa/carbidopa group lists 0 affected participants among 90 at risk, and the placebo group lists 0 affected participants among 49 at risk. These figures describe the recorded serious-event counts; they do not show that the possibility of serious harm is absent or quantify a comparative safety effect. The registry's serious-event terms list is empty, so event-level details are not reported in the registry record.

For other adverse events, the record lists 37 affected participants among 90 at risk in the levodopa/carbidopa group and 17 among 49 at risk in the placebo group. These are counts, not rates calculated for comparison. No rate, risk difference, confidence interval, or statistical test is reported in the registry record, and none should be inferred from the counts alone.

The record does not describe the definitions, severity, duration, recurrence, or timing of these other adverse events. Death values are null and therefore are not reported in the registry record; they should not be read as zero deaths. The safety figures are best understood as limited registry summaries, not as a complete assessment of comparative safety.

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

The design addresses a specific treatment question: whether oral levodopa/carbidopa added to patching differs from oral placebo with patching in children described as having residual amblyopia. The primary endpoint was amblyopic-eye visual acuity at the 18-week visit, with the stated analysis comparing mean acuity adjusted for baseline. The record also gives a measurement protocol and explains the relation between letter scores and logMAR lines.

These design details do not establish the observed treatment effect. The primary numerical comparison, confidence interval, and hypothesis-test result are not reported in the registry record. Without them, the direction and size of the contrast, and how precisely it was estimated, cannot be described. The record's primary-outcome wording also refers to a distribution of change while the analysis description refers to mean acuity; the relationship between those descriptions is not given.

The listed safety counts provide a limited account of participants recorded with serious and other adverse events. They do not supply event rates or a formal comparison, and the missing death values cannot be interpreted as zero. No conclusion about comparative safety follows from these summaries alone.

The registry record also does not provide enough detail to evaluate every feature that affects interpretation, including the full statistical analysis plan, multiplicity handling, complete imputation model, and sensitivity analyses. A completed randomized trial can contribute useful evidence, but interpretation depends on its results and methods as well as its design. The information recorded supports description of the trial question and selected methods; it does not support a conclusion about whether levodopa changes visual acuity or about the balance of benefits and harms.

13. Why This Trial Matters Statistically

This trial is statistically notable as a randomized, quadruple-masked, parallel-group Phase 3 comparison that uses a specified visual-acuity protocol and a baseline-adjusted primary analysis. The endpoint is clinically interpretable as an amblyopic-eye letter score, and the record provides the measurement detail that five letters is equivalent to one logMAR line. These features help define what was intended to be compared and how the primary outcome was measured.

The planned assessment occurred at 18 weeks, with a rapid taper of study medicine beginning at week 16. This makes timing relevant when interpreting the endpoint: the recorded primary comparison concerns acuity at that scheduled visit, not an unspecified time or a longer-term outcome. The registry also identifies secondary visual-acuity measures at several other times, which makes clear why the distinction between a prespecified primary comparison and other analyses matters.

Missing-data handling is another important statistical feature. The record reports following the ITT principle and using Monte Carlo Markov Chain multiple imputation for missing 18-week visual-acuity outcomes, while the description of the imputation inputs is incomplete. Readers therefore have a partial account of the approach but not enough information to assess its assumptions or robustness.

Finally, the primary effect estimate and its precision are not reported in the registry record. This absence limits what can be learned from the trial entry, even though design and measurement details are available. Statistical interpretation requires both an estimate and its uncertainty, along with enough methodological detail to understand how they were obtained. The record describes parts of that framework but does not provide the primary result needed to judge the observed treatment contrast.

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 important trial-specific details unavailable. The primary efficacy estimate, confidence interval, and test result are not reported, so the treatment contrast cannot be quantified or evaluated for precision. The primary outcome title refers to a distribution of change from baseline, while its description identifies a baseline-adjusted comparison of mean acuity; the record does not explain how these descriptions fit together.

The available statistical description is incomplete. Although the record states that the ITT principle was followed and that multiple imputation was used, the imputation description ends after referring to treatment group and baseline information. The missing-outcome count, full imputation model, assumptions, diagnostics, and sensitivity analyses are not reported in the registry record. The handling of multiple outcomes and analyses is also not described.

Several aspects of trial conduct are not detailed: the randomization procedure, allocation concealment, the roles covered by quadruple masking, patching schedule, adherence assessment, and the full analysis plan. The registry lists adverse-event counts but does not report event definitions, timing, severity, recurrence, or a comparative analysis. Death values are not reported in the registry record.

These limitations concern the information available in the registry entry; they do not establish that the underlying trial lacked additional analyses or documentation. They do mean that the registry record alone is insufficient to assess the magnitude and precision of the primary result, the robustness of missing-data handling, or the comparative safety profile.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Levodopa for the Treatment of Residual Amblyopia — NCT01190813.
• Registry record last updated 2016-06-02; status last verified 2016-05.
• Results first posted 2015-02-13.
• 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

NCT01190813 is a completed Phase 3 randomized, quadruple-masked, parallel-group trial sponsored by Jaeb Center for Health Research. The record lists enrollment of 139, a start date of 2010-09, and primary completion in 2014-01. The trial compared levodopa/carbidopa plus patching with oral placebo plus patching in children described as 7 to <13 years old with residual amblyopia.

The primary endpoint was amblyopic-eye visual acuity at 18 weeks after enrollment. The record describes a baseline-adjusted comparison of mean acuity and specifies measurement with the Electronic Early Treatment of Diabetic Retinopathy Study protocol. It also reports use of the ITT principle and multiple imputation for missing 18-week visual-acuity outcomes.

The registry record does not report the primary numerical treatment comparison or its precision. It lists serious and other adverse-event counts, but does not provide a complete comparative safety analysis or detailed event descriptions. The record therefore supports an account of the study design and selected methods, but not a conclusion about the observed efficacy or comparative safety findings.