The Effect of Sedation on Eye Movements: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Effect of Sedation on Eye Movements (NCT00646646), a randomized na study. The primary outcome is Dynamic Eye Movement Measures.

2. Clinical Question

3. Trial Design

The registry describes a randomized, single-masked, parallel study. Randomized allocation means that assignment to study groups is intended to use a chance-based process. A parallel design means participants are assigned to groups that receive separate study conditions rather than each participant necessarily receiving every condition. The registry does not report the allocation procedure, the identity of the masked party, or further details about masking. The study is listed as phase NA, and its status is completed.

The listed interventions are dexmedetomidine, midazolam, propofol, and saline placebo. The registry describes the first three as sedative or active-drug interventions and identifies placebo as the control. It does not report the doses, routes, timing of administration, or other treatment details in the record. The sponsor is the University of Alabama at Birmingham. The recorded study start is 2007-04, and primary completion is 2008-10.

There were 65 participants enrolled. For the primary outcome, the posted group counts are 15 for dexmedetomidine, 15 for midazolam, 15 for propofol, and 20 for placebo. The registry does not explain whether these counts reflect analysis exclusions, missing outcome data, or another feature of the outcome reporting. The safety record lists different group counts for placebo and propofol than the primary outcome record, so those safety denominators should be interpreted separately rather than assumed to match the primary outcome population.

The registry posts one outcome measure, with results for the change in dynamic eye movement measures from baseline to the sedation state, approximately 1 hr. It does not post a statistical analysis for a two-arm comparison. Details of the planned analysis, sample-size rationale, and analysis populations are not reported in the registry record.

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: A physical examination of each participant was used to assess their success in the study. Participants were excluded if they did not meat the BMI weight requirement and/or wanted to be excluded from the study.

Overall Study

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 Dynamic Eye Movement Measures, measured over baseline to Sedation State (approx. 1 hr).

The primary endpoint is the change in dynamic eye movement parameters from baseline to the sedation state, approximately 1 hr after baseline. The measure is continuous, reported as a mean, and expressed in degrees/second. A continuous outcome retains information about the magnitude and direction of changes rather than reducing the result to a simple count of participants above or below a threshold.

Saccadic eye movements are rapid movements of the eyes between points of focus. The endpoint captures changes in measured eye movement behavior over the stated study period. In general, measuring change from baseline can describe how a participant's outcome differs from their own starting measurement, which may help account for initial variation between participants. The registry does not provide further detail about which particular movement parameters were combined or how the reported change was derived.

The posted results give an arm-level mean and a 95% confidence interval for each group. The mean describes the central estimate of change in that group; the interval conveys uncertainty around that estimate under the statistical method used. These are within-group summaries. They do not directly quantify the difference between a sedative group and placebo, and the registry does not post the inferential comparisons needed to interpret such differences. The endpoint is therefore useful for describing the recorded eye movement changes, but the posted summaries alone do not establish a comparative effect.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The posted endpoint is continuous and summarized by a mean with a 95% confidence interval. A mean is a measure of the central location of a set of values. Here it represents the average recorded change in dynamic eye movement measures for each study group. The confidence interval describes the precision of that estimated mean under the analysis method used. It is not a statement that 95% of participants had changes inside the interval, nor does it describe the range of individual responses.

What does the confidence interval convey?

In general, a confidence interval combines an estimate with information about its sampling uncertainty. A narrower interval indicates greater precision under the model and calculation used; a wider interval indicates less precision. The placebo mean has a broad interval, from -77.0 to 57.0 degrees/second, while the intervals for the sedative groups are narrower. This difference in interval width is visible in the posted results, but the registry does not report the underlying variability estimates or the calculation details that would explain it. An interval containing zero is compatible with a range of possible mean changes that includes no change, as well as changes in either direction. It is not, by itself, a test comparing two assigned groups.

Why is a direct group comparison important?

The study question concerns whether sedation affects eye movements, which calls for a comparison of outcomes across assigned groups. Separate group means describe each group independently. A direct comparison estimates how far apart two groups are and quantifies uncertainty for that difference. The uncertainty for a difference cannot be read off by comparing whether two separate confidence intervals overlap. The registry reports that two-arm comparison values are missing or not estimable for this continuous endpoint. Therefore, no posted between-group estimate or inferential test is available for interpretation.

What does randomization contribute?

In general, random allocation aims to make groups comparable with respect to measured and unmeasured characteristics at the point of assignment. It can support causal interpretation when the trial is conducted and analyzed appropriately. Randomization does not guarantee that every group will have identical characteristics, particularly in a finite study, and it does not remove the need to report the analysis method and comparison estimates. The registry identifies the study as randomized but does not report the randomization procedure, concealment details, or a complete statistical plan.

Why do analysis details matter?

For a continuous endpoint, results can depend on how change is calculated, how missing measurements are handled, whether the analysis adjusts for baseline, and which participants are included. In general, adjustment for baseline can affect both the estimate and its precision. The registry identifies the outcome as a change from baseline, but does not report additional details about its derivation or model. It also does not report whether the primary analysis followed intention-to-treat principles, included only participants with observed measurements, or used another analysis population.

Over-dispersion is a general concern mainly for count outcomes when observed variability exceeds what a simple count model assumes. It is not a reported feature of this continuous mean endpoint, and no count-model results are posted for the primary outcome. More broadly, selecting a statistical model that reflects the outcome type and study design is essential; the registry record does not state which model, if any, was used for a comparative analysis.

The record lists a planning illustration based on an observed effect and stated assumptions, but no values from that illustration are needed to interpret the posted arm-level outcome summaries. Such planning calculations are not observed power and do not replace the trial's own design rationale. The sample-size justification and the trial's planned statistical analysis are not reported in the registry record. Without those details and without a posted direct comparison, the arm means and intervals support descriptive interpretation only.

10. Multiplicity, Missing Data and Analysis Populations

The registry posts one outcome measure and no secondary outcome results. It does not report whether other outcomes were collected, whether multiple measures or time points were considered during analysis, or whether any adjustment for multiple testing was planned. Multiplicity concerns arise when several statistical tests are conducted: the chance of at least one false-positive finding can increase as the number of tests grows. This is a general statistical issue, not evidence that a particular adjustment was or was not used in this study.

The stated primary outcome concerns change from baseline to the sedation state, approximately 1 hr. The registry does not report whether this was the only planned endpoint or whether there were additional planned analyses. It also does not report interim analyses, and no interim-analysis plan should be inferred from the completed status or the posted result.

Missing-data handling and analysis populations are not reported in the registry record. The primary outcome counts are 15 for dexmedetomidine, 15 for midazolam, 15 for propofol, and 20 for placebo. These counts total the enrolled number, but the registry does not explain how the analysis counts were determined or whether all randomized participants contributed a measurement. The safety record gives different placebo and propofol denominators, which further cautions against assuming a single analysis population across outcome types.

The registry does not state whether the analysis was intention-to-treat, per-protocol, or based on participants with available measurements. It also does not describe imputation or sensitivity analyses for missing observations. These omissions limit assessment of how missingness may affect the estimates and whether the analysis followed the original assignment groups.

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 0% reporting threshold.

The safety record lists serious adverse events for dexmedetomidine, midazolam, placebo, and propofol. It reports 0 affected participants in each listed group. The corresponding numbers at risk are 15 for dexmedetomidine, 15 for midazolam, 15 for placebo, and 20 for propofol. The record also reports 0 participants affected by other adverse events in each group, with the same listed group denominators.

These figures describe the adverse event counts posted in the registry. A report of 0 affected participants means that no events in that category were recorded for the listed group in this result; it does not establish that the risk is absent. The record does not list any serious adverse event terms. Death counts are not reported in the registry record.

The safety denominators differ from the primary outcome counts for placebo and propofol. The registry does not explain the difference, so the safety counts should not be substituted for the primary outcome counts or treated as evidence about the reason for the discrepancy. These summaries also do not establish comparative safety: the record does not post a statistical comparison, and the listed counts alone do not quantify uncertainty around between-group differences.

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

The registry record documents a randomized study of sedation and saccadic eye movements, with a continuous primary outcome measured as change in dynamic eye movement parameters from baseline to the sedation state, approximately 1 hr. It posts mean changes and 95% confidence intervals for three sedative groups and a placebo group. The sedative-group means are negative, and the placebo mean is positive, but the placebo estimate is imprecise relative to the estimates for the sedative groups.

Those summaries can describe what was recorded in each group, but they do not answer the comparative question on their own. The registry does not post a direct two-arm comparison, its confidence interval, or a p-value. The record states that values for a two-arm comparison are missing or not estimable. Accordingly, no comparative treatment effect can be read from the posted analyses, and the separation between arm means should not be treated as a formal test.

The results also do not establish whether the observed changes matter clinically. The registry record does not define a threshold for a meaningful change, describe the clinical consequences of changes in the measured parameters, or report patient-centered outcomes. It reports one outcome measure and no posted secondary outcome results, so broader claims about effects outside the measured endpoint are not supported by these data.

Interpretation is further limited by missing information about participant characteristics, intervention details, outcome derivation, analysis populations, missing-data handling, and the statistical plan. The registry identifies randomization and masking but provides little operational detail about either. Safety summaries report no affected participants in the listed serious-event and other-event categories, while deaths are not reported. These counts are descriptive and should not be interpreted as proof that adverse events cannot occur.

In short, the posted record gives arm-level estimates of eye movement change and their uncertainty, but leaves the main between-group inference unresolved. The absence of a comparative analysis is not evidence that the groups are equivalent, nor is it evidence that a difference is statistically established.

13. Why This Trial Matters Statistically

This trial is statistically instructive because its central question is comparative, while the posted primary results are arm-level summaries. Mean changes and confidence intervals can provide useful descriptions, but they are not substitutes for an estimated difference between a sedative group and placebo. Recognizing that distinction prevents readers from treating visual separation between group estimates as proof of a treatment effect.

The precision of the estimates also varies across groups. The placebo interval is notably broader than the intervals for the sedative groups, which illustrates how uncertainty can differ between group means. In general, precision depends on the amount of information and the variability represented in the data; the registry does not report enough detail to identify why the intervals differ. The example highlights why uncertainty should be read alongside point estimates rather than focusing on the means alone.

The record also demonstrates the importance of complete reporting. Randomization and a parallel design are identified, but the allocation and masking procedures, analysis plan, comparison estimates, missing-data methods, and analysis populations are not reported. Without those details, readers cannot fully evaluate how the primary question was tested or how robust the results may be to analytic choices.

Finally, the different safety and primary-outcome group counts show why denominators need to be interpreted in context. Counts can refer to distinct outcome records or analysis populations, and discrepancies should not be silently reconciled. Clear reporting of denominators and analysis populations is essential for understanding what each result represents. Overall, the record offers a useful example of the difference between describing observed outcomes and making an inferential claim about group differences.

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.

Several trial-specific limitations follow from the registry record. The primary outcome results are reported as group means and confidence intervals, but comparative estimates for two-arm analyses are missing or not estimable. Consequently, the central between-group question cannot be assessed from a posted treatment-versus-placebo estimate or inferential test.

The registry provides limited information about the participants. Although 65 participants were enrolled, participant characteristics and eligibility details are not reported in the registry record. This limits assessment of whom the results describe and how broadly they might apply. Doses, routes, and administration details for the study drugs and placebo are also not reported in the record.

The outcome is described as change in dynamic eye movement parameters, but the registry does not report further detail about the component parameters or the method used to derive the reported change. The statistical plan, model, baseline adjustment, missing-data approach, and analysis populations are not reported. The registry also does not explain why the safety denominators differ from the primary outcome counts for placebo and propofol.

Only one outcome measure is posted, and no secondary outcome results are reported. Whether other outcomes were planned or collected, whether interim analyses occurred, and whether multiplicity was addressed are not reported in the registry record. Death counts are also not reported. These omissions do not establish that particular procedures or events were absent; they mean that the registry record does not document them.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Effect of Sedation on Eye Movements — NCT00646646.
• Registry record last updated 2017-05-19; status last verified 2017-04.
• Results first posted 2014-05-08.
• 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 completed study, titled “The Effect of Sedation on Eye Movements,” is listed as randomized, single-masked, and parallel, with 65 participants enrolled. The interventions are dexmedetomidine, midazolam, propofol, and saline placebo. The primary outcome is the mean change in dynamic eye movement measures, in degrees/second, from baseline to the sedation state, approximately 1 hr.

Posted mean changes are -25.0 for dexmedetomidine, -115.0 for midazolam, -90.0 for propofol, and 10.0 for placebo. The registry provides 95% confidence intervals for each group but no estimable two-arm comparison. It lists 0 serious adverse events and 0 other adverse events in each safety group; deaths are not reported. Details of the statistical plan, missing-data methods, and analysis populations are not reported in the registry record.