This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Effect of Topical Aqueous Suppressants on Intraocular Gas Duration Following Pars Plana Vitrectomy (NCT01257698), a randomized na study. The primary outcome is Duration of Intraocular Gas.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01257698 |
| Phase | NA |
| Condition | Macular Hole, Retinal Detachment |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | None (open label) |
| Enrollment | 21 |
| Arms in the primary outcome | 2 |
| Lead sponsor | Mid Atlantic Retina |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns patients undergoing pars plana vitrectomy. Macular hole and retinal detachment are listed as conditions. The registry record does not report a more detailed description of the enrolled population or eligibility criteria.
Intervention
The intervention was topical dorzolamide 2%-timolol 0.5% eyedrops, described in the arms as dorzolamide-timolol topical drops. The registry record does not report a dosing schedule or the duration of treatment.
Comparator
The comparator was standard of care. The registry record does not describe the specific care used in that arm, so it is not possible to characterize what participants received beyond that label.
Primary question
The primary question was whether topical dorzolamide-timolol affected how long an intraocular gas bubble remained after pars plana vitrectomy. The primary outcome was duration of intraocular gas, measured in days, with observation described as extending up to 4 weeks. The registry record lists group means and standard deviations but no inferential comparison between the arms.
3. Trial Design
The registry describes a prospective, randomized study with a parallel-group model and no masking. Participants were assigned to topical dorzolamide-timolol drops or standard of care. The registry record lists enrollment as 21 and the study status as completed. It records a start date of 2010-02 and primary completion in 2013-06. Mid Atlantic Retina is listed as the sponsor.
The posted outcome information includes 8 participants in the dorzolamide-timolol arm and 9 in the standard-of-care arm. For duration of intraocular gas, the reported mean was 17.1 days with a standard deviation of 1.6 in the drops arm, and 18.1 days with a standard deviation of 2.4 in the standard-of-care arm. The registry record does not explain how these outcome counts relate to the enrollment figure or account for participants without posted outcome values.
Random assignment is intended to reduce systematic differences between groups, while a parallel design compares separate groups receiving their assigned approaches. The registry record does not report details of the randomization sequence, concealment, or how assignment was implemented. Masking is listed as none; further information about who knew the assigned approach is not reported in the registry record.
The registry lists one outcome measure and no posted analyses or secondary outcomes. Its arm-level summaries therefore describe the observed results, but do not supply a trial-level estimate of the difference between groups, a confidence interval, or a significance test. Those details 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.
Overall Study
| Stage | Dorzolamide-timolol Topical Drops | Standard of Care |
|---|---|---|
| STARTED | 12 | 9 |
| COMPLETED | 8 | 9 |
| NOT COMPLETED | 4 | 0 |
Reasons for not completing this period:
| Reason | Dorzolamide-timolol Topical Drops | Standard of Care |
|---|---|---|
| Protocol Violation | 4 | 0 |
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.
| Characteristic | Unit | Dorzolamide-timolol Topical Drops | Standard of Care | Total |
|---|---|---|---|---|
| Participants analysed | 8 | 9 | 17 | |
| Age, Categorical: <=18 years | Participants | 0 | 0 | 0 |
| Age, Categorical: Between 18 and 65 years | Participants | 7 | 6 | 13 |
| Age, Categorical: >=65 years | Participants | 1 | 3 | 4 |
| Sex: Female, Male: Female | Participants | 3 | 0 | 3 |
| Sex: Female, Male: Male | Participants | 5 | 9 | 14 |
| Region of Enrollment: United States | participants | 8 | 9 | 17 |
6. Primary Endpoint
The registry lists the primary outcome as Duration of Intraocular Gas, measured over Up to 4 weeks.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | days |
| Endpoint classification | Continuous Endpoint |
The primary endpoint is duration of intraocular gas, measured in days. It represents the time from the procedure until the gas bubble disappears, as tracked by participants and confirmed through weekly phone calls from the study coordinator. The stated observation period is up to 4 weeks. This outcome directly addresses the study question because the study is evaluating the duration of the intraocular gas bubble following pars plana vitrectomy.
A continuous endpoint such as duration can be described using a mean and a measure of spread. The registry reports means and standard deviations for both arms. The mean describes the central value of the recorded durations in each group; the standard deviation describes how dispersed the individual durations were around that group mean. These summaries do not, by themselves, quantify the uncertainty in the comparison between groups.
The registry does not report an analysis of time-to-event data, despite the outcome relating to the time until gas disappearance. It also does not report a median, confidence interval, or inferential comparison. The measurement procedure and the stated timeframe describe how the endpoint was intended to be observed, but details such as how incomplete monitoring or uncertain disappearance dates were handled are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The posted arm summaries show a mean duration of 17.1 days in the dorzolamide-timolol group and 18.1 days in the standard-of-care group. The corresponding standard deviations are 1.6 and 2.4. These are descriptive results for the participants whose arm-level outcome data are posted. They should not be treated as an estimate of a treatment effect with established precision.
A between-group conclusion requires more than reading the two means side by side. Statistical inference depends on an analysis that specifies how the observed data were compared and quantifies uncertainty. The registry record lists no analyses, and a two-arm comparison is not available. It does not report a confidence interval or a p-value for the primary outcome. The record therefore does not establish whether the observed difference between the displayed group means is compatible with chance variation, nor does it quantify the range of group differences consistent with the data.
The standard deviations describe variation among observed durations within each arm. They are not standard errors or confidence intervals for the means. A relatively small standard deviation does not by itself establish a precise comparison; precision also depends on the amount of usable data and the analysis. The registry record lists outcome counts of 8 and 9, while enrollment is listed as 21. The reason for the difference between those counts and enrollment is not reported in the registry record.
The randomized design is relevant because random assignment can support a fair comparison when the assigned groups are analyzed appropriately. But a design label alone does not provide the result of that comparison. The record does not give a method for handling missing outcomes, identify an analysis population, or state whether the comparison followed assignment regardless of treatment received. These details matter when interpreting group summaries.
Accordingly, the posted results can be read as descriptive summaries of duration in the two arms. They do not, on their own, show that the drops caused a change in gas duration, establish that the groups were equivalent, or determine the precision of any effect estimate. No clinical conclusion should be drawn from the numerical contrast alone.
9. Statistical Methods Explained
The registry identifies the outcome as continuous and reports each arm using a mean and standard deviation. These statistics answer different descriptive questions. The mean gives the arithmetic average of observed durations in a group. The standard deviation describes how much individual durations tend to vary around that average. Neither statistic is an estimate of the uncertainty in a between-group effect on its own.
What does a confidence interval add?
In general, a confidence interval gives a range of effect estimates compatible with the observed data under a specified statistical method. Its width reflects uncertainty: a wider interval indicates less precision, while a narrower interval indicates more precision. The interval also helps distinguish a small, precisely estimated contrast from a similar-looking contrast with substantial uncertainty. No confidence interval for the primary comparison is reported in the registry record.
What does a significance test answer?
In general, a significance test evaluates how unusual the observed data would be under a stated null hypothesis and statistical model. A p-value is not the probability that the null hypothesis is true, nor does it measure the size or clinical importance of an effect. The registry record reports no p-value or test for the primary endpoint. A statistical test cannot be inferred from the arm means and standard deviations alone without choosing additional assumptions and an analysis procedure.
Why does the analysis method matter?
Different methods can be appropriate for different data structures and estimands. A direct comparison of means may be reasonable when the target is a difference in average duration and the assumptions of the method are suitable. An analysis of time until an event may instead account for event timing and censoring, when those features are present and documented. Although the endpoint concerns time until gas disappearance, the registry record does not describe a time-to-event analysis or report how censoring was handled. The method used for the posted arm summaries is not reported in the registry record.
Randomization provides a basis for comparing assigned groups, but the analysis still needs to clarify which participants are included and how outcomes are handled. An intention-to-treat approach generally analyzes participants according to randomized assignment, regardless of treatment received. A per-protocol approach generally focuses on participants who followed specified aspects of the protocol. These are general concepts, not descriptions of the analysis used in this study; the registry record does not identify an analysis population or report either approach.
Variability also affects the ability to estimate a group comparison. Standard deviations summarize participant-to-participant spread, whereas the uncertainty of a mean or contrast depends on the amount of analyzable information and the chosen model. When data are more variable, estimates can be less precise if other conditions are similar. This is a general statistical principle; the registry record does not provide an inferential estimate that would allow the precision of this comparison to be assessed.
Some outcomes may show greater variability than a simple model assumes. In general, over-dispersion means the observed variability exceeds what a model expects. A model that ignores over-dispersion can understate uncertainty and yield overly narrow intervals or overly optimistic tests. The posted endpoint is summarized as a continuous measure with standard deviations; the registry record does not report a model, a dispersion assessment, or an over-dispersion adjustment. There is therefore no basis to say that over-dispersion was assessed or was a concern in this analysis.
The registry includes a planning assumption describing an illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such a planning exercise is hypothetical: it describes participant counts that might be needed under stated assumptions, not the probability that this completed study detected an effect. It is not observed power. The record does not report the trial's own sample-size justification or design calculation. Since no two-arm recalculation is available, no recalculated comparison or planning count can be interpreted from the posted outcome summaries.
10. Confidence Intervals for Each Arm
No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.
| Arm | Participants | Mean | Standard deviation | 95% CI for the mean |
|---|---|---|---|---|
| Dorzolamide-timolol Topical Drops | 8 | 17.100 | 1.600 | 15.762 to 18.438 |
| Standard of Care | 9 | 18.100 | 2.400 | 16.255 to 19.945 |
R code and output
arm <- c("Dorzolamide-timolol Topical Drops", "Standard of Care")
n <- c(8, 9)
m <- c(17.1, 18.1)
sp <- c(1.6, 2.4)
sd <- sp # posted standard deviations
for (i in seq_along(n)) {
se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}
CARM Dorzolamide-timolol Topical Drops 8 17.100 1.600 15.762 18.438
CARM Standard of Care 9 18.100 2.400 16.255 19.94511. Multiplicity, Missing Data and Analysis Populations
The registry lists one outcome measure and zero posted secondary outcomes. It does not report a multiplicity adjustment or a broader family of outcomes for which a shared error rate was controlled. In general, multiplicity arises when several hypotheses are tested and can increase the chance of at least one false-positive result if tests are interpreted independently. With no posted analyses, the record does not show how any multiplicity issue was handled.
The endpoint description says participants self-monitored gas-bubble duration and received weekly phone calls from the study coordinator until disappearance was confirmed. The registry record does not report the number of missing or incomplete outcome measurements, reasons for missingness, imputation methods, or sensitivity analyses. It also does not describe how uncertain or unconfirmed disappearance was treated.
Enrollment is listed as 21, while posted outcome counts are 8 and 9. The registry record does not explain the relationship between those figures, whether all enrolled participants were randomized, or whether participants were excluded from the outcome summaries. An analysis population, such as intention-to-treat or per-protocol, is not reported in the registry record. Without these details, the extent to which the posted summaries represent all randomized participants cannot be determined.
12. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Dorzolamide-timolol Topical Drops | 0 | 8 | 0.0% |
| Standard of Care | 0 | 9 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Dorzolamide-timolol Topical Drops | 0 of 8 |
| Standard of Care | 0 of 9 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Dorzolamide-timolol Topical Drops | 0 of 8 |
| Standard of Care | 0 of 9 |
The posted safety figures list 0 serious adverse events among 8 participants at risk in the dorzolamide-timolol group and 0 among 9 participants at risk in the standard-of-care group. Deaths are listed as 0 in both groups. Other adverse events are also listed as 0 among 8 and 9 participants at risk, respectively.
These counts describe the events recorded in the registry. They do not establish that no adverse events occurred outside the recorded follow-up or that the intervention cannot cause harm. The registry record does not report detailed safety definitions, event-collection procedures, follow-up duration for safety, or event-level descriptions. The absence of recorded events should therefore be read in the context of the posted counts and the information available, not as proof of safety.
13. What the Result Does, and Does Not, Mean
The registry record gives a focused account of a randomized comparison of topical dorzolamide-timolol and standard of care after pars plana vitrectomy. It reports mean intraocular gas durations and standard deviations for both arms, along with participant counts for those outcome summaries. These figures describe the posted observations and are the main numerical results available for the primary endpoint.
The record does not report a between-group statistical analysis, confidence interval, or p-value. As a result, it does not quantify the uncertainty around a treatment effect or provide a basis for deciding whether the observed arm-level contrast is distinguishable from chance variation. The means should not be converted into a causal conclusion by comparing them informally.
The findings also do not establish equivalence or rule out a meaningful difference. Equivalence requires a defined margin and an analysis designed to assess whether effects fall within that margin; such information is not reported in the registry record. Likewise, the posted summaries do not provide evidence about outcomes other than duration of intraocular gas. No secondary outcomes are posted.
The reported safety counts record no serious adverse events, other adverse events, or deaths in the listed groups. Those counts are useful descriptive information, but they do not establish that no risk exists. The registry record does not describe the full safety assessment or provide event-level details.
The appropriate statistical reading is therefore limited: the record provides descriptive arm summaries, but not an inferential answer to the primary comparison. Missing information about analysis methods, participant flow, missing outcomes, and the analysis population further limits how far the results can be interpreted.
14. Why This Trial Matters Statistically
This study illustrates why trial design labels and arm-level summaries do not replace a reported comparative analysis. Randomization is an important design feature, but readers also need to know how outcomes were analyzed, how much uncertainty surrounds the comparison, and which participants contributed data. Without those elements, a difference between displayed means remains descriptive.
The endpoint is a duration, measured through participant self-monitoring with weekly calls to confirm disappearance. That measurement process makes clear why endpoint definitions and handling of incomplete follow-up matter. The registry describes the intended confirmation procedure, but does not report how uncertain dates, missing observations, or incomplete confirmation were addressed.
The posted summaries also show why participant counts need context. Enrollment is listed as 21, while outcome counts are 8 and 9. The record does not explain that relationship. A transparent account of participant flow and analysis populations would help readers assess which observations the arm summaries represent.
Finally, the absence of posted analyses is consequential. Means and standard deviations communicate the observed values and their spread, but not the precision of a comparison. Without a reported estimate and uncertainty interval, readers cannot distinguish a well-estimated contrast from one that may be highly uncertain. This is a useful statistical lesson in reading registry results: descriptive statistics are informative, but should not be mistaken for the result of a complete inferential analysis.
15. 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 details needed to interpret the results are not reported in the registry record. Although the study is identified as randomized, the record does not describe sequence generation, allocation concealment, or implementation of assignment. Masking is listed as none, but the record does not specify which study personnel or participants knew assignments.
The registry gives enrollment as 21 and outcome counts of 8 and 9, without explaining the difference. It does not report a participant flow account, reasons for any missing outcome data, or how the analysis population was defined. These omissions limit assessment of whether the summaries reflect all randomized participants or a subset.
The primary endpoint description explains self-monitoring and weekly phone calls, but does not report how missing reports, uncertain disappearance times, or failure to confirm disappearance were handled. No inferential analysis, confidence interval, or p-value is posted. Consequently, the precision of the comparison and the method used to estimate it cannot be evaluated.
The record lists standard of care as the comparator but does not detail the care delivered in that arm. It also does not report the dosing schedule or duration for the topical drops. The absence of secondary outcomes and analysis details limits interpretation to the posted descriptive summaries and recorded safety counts.
16. Related Tutorials
17. Related Statistical Calculators
18. Sources
- ClinicalTrials.gov: Effect of Topical Aqueous Suppressants on Intraocular Gas Duration Following Pars Plana Vitrectomy — NCT01257698.
- Registry record last updated 2019-09-04; status last verified 2019-08.
- Results first posted 2019-09-04.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
19. Record Summary
The registry describes a completed, prospective, randomized, unmasked, parallel-group study sponsored by Mid Atlantic Retina. The comparison was topical dorzolamide-timolol drops versus standard of care after pars plana vitrectomy. Enrollment is listed as 21, with conditions including macular hole and retinal detachment.
The primary outcome was duration of intraocular gas in days, with observation described as up to 4 weeks. The posted mean and standard deviation were 17.1 and 1.6 for the drops arm, and 18.1 and 2.4 for standard of care. Outcome counts were 8 and 9. No analyses or secondary outcomes are posted, and no two-arm inferential comparison is reported in the registry record. The safety figures list no serious adverse events, other adverse events, or deaths in either group.