The Effect of Glaucoma Drops on of the Duration of a Pure Intraocular Gas Bubble: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Effect of Glaucoma Drops on of the Duration of a Pure Intraocular Gas Bubble (NCT01843920), a randomized na study. The primary outcome is Complete Resolution of Intraocular Gas Bubble.

2. Clinical Question

This was a randomized comparison, but the registry does not report how randomization was generated or concealed. The study was unmasked, so the record does not indicate that participants or study personnel were unaware of the assigned drops. That matters for an outcome reported by participants: knowing which drops were used could potentially affect how disappearance was perceived or reported. This is a general concern about subjective measurement, not evidence that reporting was biased in this study.

The registry lists scleral buckling as the condition, while the official title refers to scleral buckling and pneumatic retinopexy. The record does not report how many participants had each procedure, nor the distribution of gas types. It therefore does not support a more specific description of the population or separate comparisons by procedure or gas. The clinical question is best read as a comparison of the recorded groups, rather than as an answer for every surgery or gas-bubble setting.

3. Trial Design

The registry describes a completed, randomized, parallel-group study with no masking. Enrollment is recorded as 21. The comparison was between standard postoperative topical drops alone and standard postoperative drops plus timolol-dorzolamide. The registry describes the latter as glaucoma drops and gives the concentrations as timolol 0.5%-dorzolamide 2%.

The primary outcome was complete resolution of the intraocular gas bubble. The outcome description specifies duration in days and says that participants reported when they saw or felt the bubble disappear. The stated observation period was following surgery until the bubble was gone, up to 2 months. The registry does not describe a separate assessment schedule, a method for confirming disappearance, or how a report was recorded and checked.

The results list 12 participants in the group without glaucoma drops and 9 in the group with glaucoma drops. The registry's arm descriptions state that gas use involved SF6 or C3F8 in each group, but the numbers receiving each gas are not reported in the registry record. The record also does not show whether procedure type or gas type was considered in the analysis.

Although allocation is described as randomized, details of sequence generation, concealment, and any stratification are not reported in the registry record. The record does not explain whether the assigned treatment was followed as intended, whether participants changed or stopped drops, or whether deviations were handled in the analysis. These details would help readers assess how the randomized comparison was conducted, but their absence does not by itself establish that a particular problem occurred.

The study is marked completed, with start recorded as 2011-06 and primary completion as 2013-04. The registry lists no analyses. It does not report a statistical analysis plan, sample-size justification, interim analyses, or a prespecified method for handling incomplete outcome reports. Consequently, the posted group summaries can be described, but the record does not provide enough information to reconstruct the trial's intended inferential analysis.

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 Complete Resolution of Intraocular Gas Bubble, measured over Following surgery, until gas bubble is gone. Up to 2 months..

The primary endpoint is the time from surgery until complete resolution of the intraocular gas bubble, expressed in days. The registry says that participants reported the time when they saw or felt the bubble disappear, and gives a follow-up period extending until disappearance, up to 2 months. The posted summaries report a mean duration and a full range for each treatment group.

Duration is useful for describing how long the gas bubble remained after surgery. Recording time rather than only whether resolution occurred can retain information about variation in timing across participants. In general, a duration endpoint can be clinically interpretable when the event and its timing are defined consistently. Here, the event is participant-reported disappearance; the registry does not describe independent confirmation or more detailed measurement procedures.

The outcome is not presented as a time-to-event analysis in the registry record. No event-time methods, censoring rules, or treatment of participants whose bubble had not resolved by the end of observation are reported. The record also does not state whether duration was measured from the date of surgery in every case or how uncertain reports were handled. Those details affect interpretation of duration data and should not be inferred from the endpoint label alone.

The primary endpoint reflects reported bubble duration, not a direct measure of another clinical outcome. The record includes a secondary outcome concerning participants with return of intraocular pressure to normal levels, but the endpoint information available for that outcome does not establish a broader benefit or harm. The statistical interpretation should therefore stay tied to the specific recorded outcome and its measurement method.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

General statistical explanation: a group mean is the arithmetic average of the recorded outcome values. It provides a compact description of the center of a distribution, but it does not describe every participant's outcome or how widely values vary. In this study, the registry reports mean duration in days for each treatment group, along with a full range. The mean and range answer different descriptive questions: the mean summarizes the center, while the range identifies the endpoints of the observed values.

What does the full range tell a reader?

General statistical explanation: a range gives the smallest and largest observed values in a group. It can show the span of recorded outcomes, but it does not reveal how observations are distributed within that span. A range is sensitive to extreme observations and usually becomes wider as more observations are recorded. It is not an estimate of uncertainty about the mean, and it should not be read as a confidence interval. Here, the registry reports the full range, not a standard deviation or another measure of spread that would describe variation around the mean in more detail.

What would a confidence interval add?

General statistical explanation: a confidence interval is an interval estimate that conveys the uncertainty associated with an estimated quantity, such as a group mean or a contrast between groups. Its interpretation depends on the design, analysis method, and assumptions. The registry record does not report a confidence interval for either group mean or for the comparison. The posted ranges cannot substitute for one. The record also does not provide a standard error or standard deviation from which a reader could assess precision using the posted summaries.

Why is a direct comparison important?

General statistical explanation: when the question concerns whether two randomized groups differ, an analysis should estimate a between-group contrast and its uncertainty. Separate summaries for each group are useful but do not, by themselves, quantify uncertainty in that contrast. The registry records no analyses and does not report a test statistic, p-value, confidence interval, or adjusted comparison for the primary outcome. A reader should therefore avoid treating the difference in the posted means as a tested or established treatment effect.

The comparison is randomized and parallel according to the registry. In general, randomization is intended to make assigned groups comparable in expectation, reducing the risk that known or unknown baseline factors systematically determine assignment. The design's value depends on how allocation was conducted and preserved. The registry does not report the randomization method, concealment, or stratification, so those features cannot be assessed. Nor does the record report baseline characteristics that would help describe the groups at entry.

How does unmasked, participant-reported measurement matter?

General statistical explanation: masking can reduce the opportunity for expectations about assignment to influence care, assessment, or reporting. The study is recorded as having no masking. The endpoint was reported by participants based on seeing or feeling the bubble disappear, so the result relies on subjective reporting rather than a measurement procedure described as independent. This creates a potential source of measurement variation. It does not show that any participant report was inaccurate or that bias occurred; the record simply does not provide information to rule out such influences.

The registry does not describe the timing of outcome checks, instructions given to participants, or any confirmation process. Those methods could affect how consistently the event time was captured. The description says follow-up continued until the bubble was gone, up to 2 months, but does not state how an observation that had not resolved by that limit was analyzed. General methods for duration outcomes may need to account for incomplete observation, sometimes called censoring, but the registry does not report whether or how such methods were used.

What do the planning assumptions mean?

General statistical explanation: sample-size planning estimates how many participants may be needed to detect a specified effect under stated assumptions. The registry describes its sample-size assumptions as a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It also states that the effect to detect is expressed as a fraction of the observed effect. These assumptions describe an illustrative planning calculation, not the trial's original design rationale and not an observed-power result. Numeric planning values are not reported in the registry record in the registry record for this analysis. The registry does not report the trial's own sample-size justification.

More generally, over-dispersion means that observed variability is greater than a statistical model assumes. When that occurs, methods that fail to account for the extra variability can understate uncertainty. The registry does not report an analysis model for the primary endpoint, so there is no basis to say whether over-dispersion was assessed or relevant to the sponsor's analysis. The duration endpoint's distribution and model fit are not described.

The posted summaries can be read as descriptive statistics for the recorded groups. They are not a replacement for a prespecified analysis, complete outcome accounting, or an uncertainty estimate. No adjusted analysis or covariate strategy is reported. The registry also does not report whether procedure type, gas type, or other baseline characteristics were included in any analysis. Any such approach would be speculation, so interpretation should remain limited to the group means and ranges recorded.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and identifies one secondary outcome: the number of participants with return of intraocular pressure to normal levels. It records no analyses. The record does not explain how the primary and secondary outcomes were prioritized for statistical testing, whether multiple comparisons were planned, or whether any adjustment for multiplicity was used. Multiplicity is a general concern when several outcomes or comparisons are tested: the more opportunities there are to declare a finding, the more important it is to interpret each result in the context of the analysis plan. No specific multiplicity procedure can be attributed to this study from the registry record.

Missing-data handling is also not reported. The primary outcome description specifies participant reporting until the bubble is gone, up to 2 months, but does not state whether all participants posted an outcome, whether any reports were incomplete, or how unresolved bubbles were treated at the end of observation. There are no reported methods for imputation, sensitivity analysis, or handling of incomplete follow-up. The absence of these details does not establish that outcome data were missing; it means the registry record does not describe their completeness or treatment.

The analysis population is not reported. The record does not say whether results include all randomized participants, only those who followed their assigned drops, or another defined group. It also does not report participant flow, treatment adherence, protocol deviations, or exclusions from the primary endpoint analysis. These details matter because excluding participants after randomization can affect the comparability that random assignment is intended to create. Without this information, the group values can be described, but the population represented by the summaries cannot be fully characterized.

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 serious adverse event fields report 0 affected participants among 12 at risk in the group without glaucoma drops and 0 affected participants among 9 at risk in the group with glaucoma drops. These are the serious-event figures recorded for the groups. The registry does not list serious adverse event terms.

A zero in these fields means that no serious adverse events are recorded as affecting participants in the specified groups in the posted safety results. It does not show that the true risk is zero, and it does not establish that the groups have equivalent safety. General statistical interpretation: when no events are observed, uncertainty about an underlying event rate can remain, especially when the number of participants observed is limited. The registry does not provide confidence intervals or a formal safety comparison.

The deaths field is null for both groups, so deaths are not reported in the registry record; null should not be interpreted as a reported count of zero. The registry also records 0 participants with other adverse events among 12 at risk in the group without glaucoma drops and 0 among 9 at risk in the group with glaucoma drops. These fields do not provide event details or establish the completeness of safety surveillance. The results should be read as the registry's recorded safety counts, not as evidence that no adverse events could occur.

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

The posted primary results describe mean gas-bubble durations of 40.4 days for participants receiving standard postoperative drops alone and 37.8 days for participants receiving timolol-dorzolamide in addition to standard postoperative drops. The reported full ranges are 27.0 to 51.0 days and 29.0 to 50.0 days, respectively. These values summarize the recorded groups; the mean is descriptively lower in the group assigned glaucoma drops.

Those summaries do not establish whether the groups differ beyond chance variation. No formal primary-outcome analysis, confidence interval, or p-value is recorded. They also do not establish that the drops caused any observed difference. Randomization is a useful design feature, but details needed to assess its conduct and the analysis population are not reported, and the trial was unmasked with a participant-reported endpoint.

The result does not show how findings vary by type of surgery or gas. The registry mentions SF6 or C3F8 in both arm descriptions and lists scleral buckling as a condition, while the official title also refers to pneumatic retinopexy. Counts and separate results for these categories are not reported in the registry record. It is therefore not possible to conclude from the posted summaries that the same pattern applies across procedures or gas types.

The record also does not explain missing outcome handling or what happened to any participant whose bubble had not resolved by the end of the stated observation period. There is no reported analysis population or participant-flow account. Such omissions limit understanding of who contributed to the summaries and how completely the endpoint was observed.

The safety fields record no serious adverse events in either group, while the deaths fields are not reported. Those entries are descriptive and do not prove absence of risk or establish a safety difference. Overall, the registry supports a narrow account of the reported group means, ranges, and adverse-event fields. It does not support a definitive claim about efficacy, causal effect, statistical significance, or safety.

13. Why This Trial Matters Statistically

This trial is statistically informative as an example of the distinction between randomized design and complete inferential reporting. Randomization is intended to support fair comparisons, but the registry record does not document how the allocation sequence was generated or concealed, which participants were included in the analysis, or how incomplete outcomes were handled. A study's design label alone cannot answer those questions.

The endpoint also highlights the importance of measurement methods. Duration until a gas bubble is reported to disappear is understandable as a participant-centered measure, but the registry describes no masking or independent confirmation. In general, subjective outcomes can be influenced by how participants recognize and report an event. Clear definitions and consistent assessment procedures help readers judge the reliability of such measurements; those details are not reported.

The posted means and ranges make a descriptive comparison possible, while the absence of a formal analysis means that precision is not. This is a useful statistical distinction: a numerical difference between group summaries is not itself evidence that the underlying groups differ. Confidence intervals or another uncertainty estimate would help quantify what the data can support, but no such estimate is recorded for the primary comparison.

The record's mention of more than one gas type and procedure context also illustrates why subgroup information matters. Overall summaries may combine participants with different clinical or procedural characteristics. Without counts or stratified results, readers cannot determine whether the group summaries conceal variation across those contexts. This is not a reason to infer that such variation exists; it is a boundary on the questions the posted results can answer.

Finally, planning calculations should not be confused with trial evidence. The registry describes planning assumptions based on the observed effect, but those calculations are illustrations rather than observed power or proof that the original study was adequately sized. The registry does not report its own sample-size justification. Keeping design, measurement, estimation, and planning distinct helps prevent descriptive results from being interpreted more strongly than the record supports.

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 details about the study population and procedures unresolved. Scleral buckling is listed as the condition, but the official title also names pneumatic retinopexy. The arm descriptions mention SF6 or C3F8, without reporting how many participants received each gas or how surgery type was distributed. The results cannot therefore be separated by procedure or gas, and the exact population represented by each group is not fully described.

The primary endpoint depends on participants reporting when they saw or felt the bubble disappear. The registry says the study was unmasked but does not describe the reporting instructions, assessment schedule, or any method for confirming the event. These omissions limit assessment of how consistently the endpoint was measured. They are potential interpretive limitations, not evidence that reporting was inaccurate.

The registry does not report baseline characteristics, allocation concealment, treatment adherence, protocol deviations, participant flow, or the analysis population. It also does not state whether all participants had a complete duration result or how unresolved bubbles at the end of follow-up were represented. Without these details, readers cannot fully assess comparability after randomization or the completeness of outcome observation.

Statistical reporting is limited to group means and full ranges for the primary endpoint. No standard deviations, confidence intervals, formal comparison, or adjusted estimates are recorded. The registry lists no analyses and does not report a statistical analysis plan, sample-size justification, or multiplicity strategy. These limitations prevent assessment of statistical precision and the robustness of an inferential conclusion.

The safety record lists no serious adverse events and reports no deaths count. It does not provide serious-event terms or detailed safety follow-up information. As a result, the safety fields should be interpreted narrowly as posted counts, not as a comprehensive account of all possible harms.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Effect of Glaucoma Drops on of the Duration of a Pure Intraocular Gas Bubble — NCT01843920.
• Registry record last updated 2018-05-30; status last verified 2018-04.
• Results first posted 2017-02-06.
• 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

NCT01843920 is recorded as a completed, randomized, parallel-group study with no masking. Enrollment is recorded as 21. It compares standard postoperative topical drops alone with standard postoperative drops plus timolol-dorzolamide, described as timolol 0.5%-dorzolamide 2%.

The primary outcome is participant-reported time in days until complete resolution of an intraocular gas bubble, with follow-up until disappearance, up to 2 months. The registry reports a mean of 40.4 days and a full range of 27.0 to 51.0 days for the group without glaucoma drops, and a mean of 37.8 days and a full range of 29.0 to 50.0 days for the group with glaucoma drops.

No formal analyses are recorded. Confidence intervals, p-values, missing-data methods, analysis populations, and the study's own sample-size justification are not reported in the registry record. Serious adverse event fields record 0 affected participants in each group; deaths are not reported.