Effect of Travoprost 0.004% on Retinal Oximetry in Primary Open Angle Glaucoma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effect of Travoprost 0.004% on Retinal Oximetry in Primary Open Angle Glaucoma (NCT01711177), a non-randomized na study. The primary outcome is Blood Oxygenation.

2. Clinical Question

The registry frames the question around whether retinal or ocular venous oxygenation differs among normal controls, glaucoma suspects and people newly diagnosed with glaucoma, with travoprost administered to the newly diagnosed group. The primary outcome is described as blood oxygenation measured during a one-hour appointment. The summary explains that a spectrophotometer linked to a camera is used to assess oxygen in the veins from characteristics of the blood.

This design combines a group comparison with treatment in one group, but the record does not describe randomized allocation. The groups differ in glaucoma status and treatment, so a difference in oxygenation could reflect group characteristics, treatment, or other factors. The registry does not report results that would allow those possibilities to be assessed. It also does not report a treatment effect estimate, a confidence interval, or a statistical test for the primary outcome.

3. Trial Design

The registry describes a completed, nonrandomized, parallel-group study of primary open-angle glaucoma. Its listed allocation is nonrandomized, and masking is listed as none. The study began in 2012-10 and reached primary completion in 2013-03. The listed enrollment is 14. The registry summary describes a recruitment plan of 10 people in each of three groups, for a planned total of 30; the recorded enrollment is therefore different from the plan in the summary. The reason for that difference is not reported in the registry record.

The three groups are normal controls, glaucoma suspects, and people newly diagnosed with glaucoma. The normal control and glaucoma-suspect groups are described as receiving placebo, while the newly diagnosed group is described as receiving travoprost. The summary states that treatment is administered only to the suspected or diagnosed groups, while the arm descriptions specify placebo for the glaucoma-suspect group. The travoprost concentration is also inconsistent: the study title names Travoprost 0.004%, but the newly diagnosed arm description gives Travoprost (0.04%). The registry record does not resolve these inconsistencies.

A nonrandomized design does not ensure that groups are comparable at baseline. Here, group membership is defined by glaucoma status, and treatment is associated with group membership rather than described as randomly assigned. Consequently, a contrast between groups cannot by itself isolate a treatment effect. No protocol details describing adjustment for group differences are reported in the registry record.

The record identifies one primary outcome and lists no analyses. It does not report the full recruitment flow, the number included in each primary-outcome analysis, or the methods used to handle incomplete measurements. Although the study status is completed, the registry record does not provide numerical results for the primary endpoint. The sponsor is Université de Montréal.

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

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 Blood Oxygenation, measured over 1 hour.

The primary endpoint is titled Blood Oxygenation. It is a continuous measure expressed as a percentage of oxygenation, with the stated summary parameter being the mean and the stated dispersion being a 95% confidence interval. The measurement is described as being collected during a one-hour appointment for each subject. The registry summary says that a spectrophotometer linked to a camera measures oxygen in ocular veins using characteristics of the blood.

Oxygenation is relevant to the study question because the registry describes prior interest in a possible link between glaucoma and changes in oxygen in the veins of the eye. In general, a continuous measurement can retain more information about variation across people than a simple classification into categories. Reporting a mean describes the average measured level in a group; a confidence interval describes uncertainty around an estimated mean under the statistical assumptions used. These are general interpretations of the stated endpoint and summary method, not claims about the observed values in this study.

The outcome description does not provide measurement units beyond percentage of oxygenation, the specific venous location, the measurement protocol, or the handling of repeated readings. Those details are not reported in the registry record. Most importantly, the record gives no group means or confidence intervals. The endpoint definition therefore identifies what was intended to be measured, but does not establish what the measurements showed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The methods below explain general statistical concepts relevant to the design and outcome described in the registry record. They do not imply that any particular analysis was conducted. The record lists the primary endpoint as a continuous outcome, with the mean and a 95% confidence interval as the intended summary. It lists no analysis results, so the methods used for an actual estimate are not reported in the registry record.

What does the mean describe?

For a continuous outcome, the mean is the arithmetic average of the values included in a group summary. It gives a measure of the group's central level, but does not show how widely individual measurements vary. Two groups could have similar means while differing in the spread or shape of their measurements. For that reason, interpretation of a mean can also depend on the distribution of observations and the amount of missing data. These are general statistical considerations; the registry record does not report group-level distributions for blood oxygenation.

What does a 95% confidence interval convey?

A confidence interval gives a range of values compatible with the data under a specified statistical procedure and its assumptions. In general, a 95% confidence interval is built by a method that, over repeated use in comparable circumstances, would contain the underlying parameter at the stated rate. It is not a guarantee that a particular interval contains the true value, and it does not describe the range containing most individual participants' measurements. An interval around a mean concerns uncertainty in the estimated mean, not individual variability. Since no intervals are posted for this endpoint, the precision of the group means cannot be evaluated.

Why does allocation matter?

Random allocation, when used, can help balance measured and unmeasured baseline characteristics across treatment groups in expectation. This record lists nonrandomized allocation and describes groups formed by glaucoma status. As a result, differences in oxygenation between groups could be associated with their underlying clinical differences, treatment, or other factors. Statistical adjustment can sometimes address measured differences, but it cannot automatically remove bias from unmeasured or poorly measured factors. No adjustment method is reported in the registry record, and there are no posted data with which to assess baseline balance.

The parallel-group model means the record describes separate groups rather than a crossover in which each participant is described as receiving each condition in sequence. The absence of masking means that masking is listed as none. In general, lack of masking can affect measurement or other study processes, depending on how outcomes are collected. The record does not describe whether the oxygenation measurement was interpreted without knowledge of group membership, so that detail is not reported in the registry record.

What can be inferred from group contrasts?

A difference between group means is a descriptive contrast. For a causal treatment interpretation, the groups must be sufficiently comparable, and the analysis must address the design and relevant sources of bias. In this study, treatment and glaucoma status are linked in the arm descriptions: the newly diagnosed group is described as treated with travoprost, while the control and suspect groups are described as receiving placebo. Thus, a group contrast would not cleanly separate a treatment association from differences related to group status. The registry record does not post a contrast estimate, an uncertainty interval for a contrast, or a model intended to address this issue.

Confidence intervals and significance tests answer related but distinct questions. An interval communicates a range of uncertainty for an estimate, while a test evaluates compatibility with a specified null hypothesis under its assumptions. Neither, by itself, establishes that a difference is clinically meaningful or causal. In this case, there are no posted estimates, intervals or test results to interpret.

Why might over-dispersion matter?

Over-dispersion is a general concern for some outcomes when observed variability is greater than a chosen statistical model expects. It is especially discussed for count data, where a simple model may underestimate uncertainty if observations vary more than the model allows. Blood oxygenation is recorded as a continuous percentage, not as a count outcome. The record does not report a model or variance diagnostics, so there is no basis to state that over-dispersion was assessed or present. More generally, an analysis should use uncertainty estimates that fit the outcome distribution and study structure.

How should planning calculations be read?

A sample-size calculation is a planning tool that relates a target effect, variability assumptions, significance level, allocation and desired power to a required sample size. The stated planning illustration is based on the observed effect, assumes a two-sided significance level of 0.05, equal allocation between two arms and a normal approximation, and considers an effect specified as a fraction of the observed effect. It is an illustration rather than evidence that the original study was planned using those assumptions. The registry record does not report a prospective sample-size justification, the assumptions used for the original recruitment plan, or numerical planning outputs. Planning sample sizes should not be called observed power, and they do not establish the probability that the study's findings are correct.

The record's recruitment summary describes 10 people per group and 30 in total, whereas recorded enrollment is 14. This difference makes clear why an intended enrollment and an actual enrollment should be distinguished. The reason for the difference is not reported in the registry record. Nor does the record state how many participants had usable measurements for the primary endpoint. Without analysis denominators and the distribution of the observations, readers cannot reconstruct an estimate or assess how much information the primary endpoint analysis contained.

Finally, the registry lists one primary outcome and no analysis results. It does not report the statistical model, any covariates, the handling of repeated measurements, or the procedure for constructing the confidence interval. Those methods should not be inferred from the fact that the outcome is continuous or that a mean and confidence interval were specified. The outcome definition and design permit a general description of what investigators intended to compare, but not a reconstruction of the analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies one primary outcome, Blood Oxygenation. It does not report a multiplicity adjustment, a prespecified hierarchy of tests, or details of any secondary outcomes. The number of outcomes listed in the registry is one, but the statistical procedures for controlling the risk of false-positive findings across possible comparisons are not reported in the registry record. Since no analysis results are listed, the effect of any multiplicity procedure cannot be assessed.

Missing-data handling is also not described. The record does not state whether every enrolled participant completed the oxygenation measurement, how incomplete appointments or unusable readings were handled, or whether any imputation method was used. It does not report the number analyzed for the primary endpoint. The safety group counts should not be assumed to be primary-outcome analysis denominators.

The registry does not define an analysis population, such as all enrolled participants or a subset with measurements available. It therefore does not report which participants contributed to a primary analysis or how any departures from the intended measurement process were treated. In general, missing data can affect estimates if the chance of missingness is related to participant characteristics or outcome values. The nature and extent of missingness in this study are not reported in the registry record, so its potential influence cannot be evaluated.

The listed analysis count is zero. This means that analysis results are not listed in the record; it does not establish that investigators performed no analyses. No statistical analysis plan, interim analysis process, or prespecified approach to missing values is reported in the registry record.

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 zero serious adverse events for each of the three groups. It lists zero other adverse events for each group as well. The numbers shown as at risk are 10 for the normal control group and 3 for each of the glaucoma-suspect and newly diagnosed glaucoma groups. These are the safety figures as recorded, and should not be treated as primary-outcome denominators.

The safety record lists deaths as null for each group. A null entry is not the same as an explicit count of zero; deaths are not reported in the registry record. The record also does not provide serious-event terms or event descriptions.

These figures describe what is entered in the registry, not proof that no adverse events occurred. The safety counts are small and unequal across groups, and the listed at-risk counts do not match the planned recruitment description. The registry record does not explain these differences or define the period covered by the safety counts. The nonrandomized design also means that these group figures cannot establish a comparative safety effect. They should be read as registry entries, not as evidence that treatment is safe or unsafe.

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

The record establishes that investigators planned to compare mean ocular blood oxygenation across normal controls, glaucoma suspects and people newly diagnosed with primary open-angle glaucoma. It also describes travoprost treatment for the newly diagnosed group and placebo for the other groups. The primary measure was to be recorded as a percentage of oxygenation, with the mean and a 95% confidence interval specified. These details describe the question and intended outcome; they are not outcome findings.

No numerical results for blood oxygenation are reported in the registry record. Consequently, the posted record does not show whether the groups had different mean oxygenation, how large any difference may have been, or how precisely it was estimated. It also does not support a claim that travoprost changed oxygenation, because no treatment estimate or comparison is reported and treatment is tied to group membership in a nonrandomized design.

The planned recruitment described in the summary is 10 people per group and 30 overall, while recorded enrollment is 14. The record does not explain why enrollment differed from the plan or state how many people contributed to endpoint analyses. The drug concentration is inconsistently described as Travoprost 0.004% in the title and Travoprost (0.04%) in the arm description. These uncertainties limit the detail with which the intervention and analysis can be characterized.

In general, an observed group difference would not automatically establish that treatment caused it. Group differences can reflect clinical status and other characteristics, particularly when allocation is not randomized. An uncertainty interval, if reported, would help describe precision but would not remove bias from a nonrandomized comparison. In this case, neither estimates nor intervals are available in the registry record.

The appropriate interpretation is therefore limited: the registry describes a completed study with a specified continuous endpoint and a nonrandomized, parallel-group design, but it does not provide results that answer the stated comparison. Absence of posted results is not evidence of no difference, just as the study aim is not evidence of a difference. No clinical conclusion about treatment should be drawn from this record alone.

13. Why This Trial Matters Statistically

This study is statistically notable because its clinical question spans groups that differ by glaucoma status, while treatment is described for only one of those groups. The distinction between a descriptive comparison and a causal treatment comparison is central. A difference in oxygenation across the groups, if one had been reported, could not be attributed to travoprost alone without addressing the nonrandomized allocation and the differences that define the groups.

The record also illustrates why planned recruitment and recorded enrollment should be kept distinct. The summary describes 10 people in each group and a planned total of 30, while the registry lists enrollment of 14. The record does not explain that difference, and it does not give primary-outcome analysis counts. Readers therefore cannot assume that the planned group sizes were achieved or that every enrolled person contributed to the endpoint.

Clear outcome reporting is equally important. A mean and 95% confidence interval are named as the intended summary, but no values are posted. Without them, neither the size of a possible difference nor its precision can be evaluated. A completed status and a detailed outcome definition do not substitute for outcome estimates.

Finally, the intervention concentration differs between the title and the arm description. This is a basic reporting inconsistency that affects how precisely the treatment can be identified. Together, the design, enrollment and reporting details demonstrate how statistical interpretation depends not only on the chosen endpoint but also on group formation, analysis denominators, and complete, internally consistent results.

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 does not report outcome values, group means, confidence intervals, contrast estimates, or test results. This is the most direct limitation for interpreting the study: the stated primary question cannot be answered from the posted results. The record lists zero analyses, but does not explain whether analyses were conducted elsewhere or whether results were unavailable for another reason.

The design is nonrandomized and unmasked. Group membership is linked to glaucoma status, and the newly diagnosed group is described as receiving travoprost while the normal-control and glaucoma-suspect groups are described as receiving placebo. These features limit causal interpretation of any group differences. Baseline characteristics, adjustment methods and procedures to reduce measurement bias are not reported in the registry record.

Enrollment is recorded as 14, while the summary describes planned recruitment of 10 people per group and 30 in total. The reason for this discrepancy is not reported. The record does not give group-specific enrollment for the primary outcome, numbers with usable measurements, or the handling of missing observations. The safety counts do not establish those analysis numbers.

The study title specifies Travoprost 0.004%, whereas the newly diagnosed group description specifies Travoprost (0.04%). This discrepancy is not resolved in the registry record. The record also does not describe the measurement protocol in enough detail to assess repeatability, the exact venous measurement site, or how multiple readings were summarized. The appointment duration is described as one hour, but details of measurement timing within that appointment are not reported.

Lastly, no statistical analysis plan, sample-size justification, multiplicity strategy or missing-data method is reported in the registry record. The available information is sufficient to describe the intended endpoint and broad design, but not to evaluate the analysis or determine the study's empirical findings.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Effect of Travoprost 0.004% on Retinal Oximetry in Primary Open Angle Glaucoma — NCT01711177.
• Registry record last updated 2016-07-28; status last verified 2016-06.
• Results first posted 2016-07-28.
• 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, nonrandomized, parallel-group study of primary open-angle glaucoma, with no masking listed. It reports enrollment of 14 and identifies normal controls, glaucoma suspects and people newly diagnosed with glaucoma. The summary describes a recruitment plan of 10 people in each group, for a planned total of 30.

The primary endpoint is mean blood oxygenation, expressed as a percentage of oxygenation and summarized using a 95% confidence interval. Measurements are described as taking place during a one-hour appointment. The normal control and glaucoma-suspect groups are described as receiving placebo, while the newly diagnosed group is described as receiving travoprost. The treatment concentration is inconsistent within the record.

The registry lists no analysis results and provides no numerical primary-outcome estimates. It records zero serious and other adverse events in the listed groups, while deaths are not reported. The sponsor is Université de Montréal. The study began in 2012-10 and reached primary completion in 2013-03.