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 Post Market Surveillance of OZURDEX® for Branch Retinal Vein Occlusion (BRVO) and Central Retinal Vein Occlusion (CRVO) (NCT01568021), a registered phase not stated study. The primary outcome is Time to First Re-treatment.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01568021 |
| Phase | Phase not stated |
| Condition | Retinal Vein Occlusion, Macular Edema |
| Allocation | Not Stated |
| Design model | Not Stated |
| Masking | Not Stated |
| Enrollment | 100 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Allergan |
| Results posted | Yes |
2. Clinical Question
Population
The study concerns people with retinal vein occlusion, including branch retinal vein occlusion (BRVO) and central retinal vein occlusion (CRVO), and macular edema. The primary outcome population is described as all participants with complete data. The number of participants with complete data is not reported in the registry record.
Intervention
The study description focuses on OZURDEX®, a dexamethasone 700 ug intravitreal implant. The arm description says a single dose may be repeated over 1 year according to standard of care in clinical practice. At the same time, the registry lists “No Intervention” and states that no intervention was administered in the study. This leaves the distinction between routine clinical treatment and study-assigned treatment unclear in the record.
Comparator
No like-for-like control comparison is described. The registry record identifies the study as observational and says that allocation was not stated. The listed arm does not establish a randomized comparison or a separate untreated control group, so the record does not support a treatment-versus-control interpretation.
Primary question
The primary endpoint asks how much time, in days, elapsed between the first OZURDEX® administration and the following administration in the study eye. It is defined as time to first re-treatment, assessed over 1 Year, and summarized by a median with a 95% Confidence Interval. The registry record does not report the median or its interval, so it does not establish the observed timing of re-treatment.
The brief summary describes a multicenter observational study intended to assess efficacy and tolerability in clinical practice and to assess when patients are considered for re-treatment. The secondary outcomes concern change from baseline in best corrected visual acuity and central retinal thickness measured by optical coherence tomography. These outcomes provide additional clinical measures, but their results are not reported in the registry record.
3. Trial Design
This is a completed, multicenter observational study sponsored by Allergan. The registry lists enrollment of 100 participants, a study start of 2011-10, and primary completion of 2013-11. Its stated purpose was to assess OZURDEX® efficacy and tolerability in clinical practice and the timing of consideration for re-treatment. These descriptions indicate observation of routine care rather than a randomized treatment comparison.
The registry lists “No Intervention” as the intervention and states that no intervention was administered. In contrast, the arm description refers to a single dose of dexamethasone 700 ug intravitreal implant that may be repeated over 1 year according to standard of care in clinical practice. These statements are not fully aligned. The record does not clarify whether treatment decisions were made entirely outside the study or how treatment exposure was recorded and analyzed. It also does not state an allocation method.
The primary outcome is time to first re-treatment among all participants with complete data. The record defines the interval from the first administration to the following administration in the study eye. Visual acuity and central retinal thickness measured by optical coherence tomography are listed as secondary outcomes. The registry lists 3 outcome measures and 0 analyses. It does not provide a detailed statistical analysis plan, participant flow, or outcome results for the primary or secondary measures.
Because the study is observational and no like-for-like control comparison is identified, its design does not separate the effects of treatment from other clinical decisions or participant characteristics. The record gives no basis for treating the listed arm as a randomized comparison group. It also does not report the study's sample-size justification or whether any interim analyses were planned or conducted.
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: This was a Post-Marketing Surveillance Study of OZURDEX®. 100 participants who received OZURDEX® as standard of care in clinical practice were enrolled in the study. Only 99 participants who had data recorded at Baseline and Follow-up were included in the analyses.
Overall Study
| Stage | OZURDEX® |
|---|---|
| STARTED | 99 |
| COMPLETED | 83 |
| NOT COMPLETED | 16 |
Analysis population for the primary outcome, as defined in the registry: All Participants with complete data.
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 | OZURDEX® |
|---|---|---|
| Participants analysed | 99 | |
| Age, Customized: < 45 years | participants | 1 |
| Age, Customized: 45 to 65 years | participants | 24 |
| Age, Customized: > 65 years | participants | 74 |
| Sex: Female, Male: Female | Participants | 41 |
| Sex: Female, Male: Male | Participants | 58 |
6. Primary Endpoint
The registry lists the primary outcome as Time to First Re-treatment, measured over 1 Year.
| Element | Registry entry |
|---|---|
| Result type | Median |
| Measure of spread | 95% Confidence Interval |
| Unit | days |
| Endpoint classification | Time-to-Event Analysis |
The primary endpoint is time to first re-treatment, measured in days. The record defines it as the time between the first administration of OZURDEX® and the following administration in the study eye. The stated timeframe is 1 Year, and the planned summary measure is the median with a 95% Confidence Interval. The endpoint population is all participants with complete data.
Time-to-event endpoints describe how long it takes for a specified event to occur. In this study, the event is a subsequent administration, not a change in visual acuity or retinal thickness. Such an endpoint can describe the timing of a clinical decision or event across follow-up, while allowing a distribution of times rather than focusing only on an average. A median identifies the central point in the observed time distribution when it can be estimated; it does not show the range of individual experiences.
The confidence interval expresses uncertainty around the estimated median under the analysis assumptions. A narrower interval indicates greater precision, while a wider interval indicates less precision. The registry record gives the endpoint definition and intended summary but does not report the median, confidence limits, number of re-treatment events, or handling of participants whose follow-up ended before re-treatment. Consequently, the endpoint's observed value and precision cannot be assessed from the registry record.
The secondary outcomes—change from baseline in best corrected visual acuity and change from baseline in central retinal thickness by optical coherence tomography—address different clinical measurements. Their inclusion does not replace the primary time-to-event question, and their outcome estimates are not reported in the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record identifies time to first re-treatment as the primary outcome and specifies a median and 95% Confidence Interval over 1 Year. It does not report the median or the interval limits. As a result, the posted record does not show how long participants waited before re-treatment, how variable those times were, or how precisely the median was estimated. No numerical conclusion about the primary endpoint can be drawn from the endpoint definition alone.
The record describes 100 enrolled participants, but the primary population is all participants with complete data. The number with complete data, and the number contributing information to the time-to-event outcome, are not reported in the registry record. Enrollment should not be treated as the analysis population without those details. The registry also lists 0 analyses, and does not include reported estimates for the primary outcome or the secondary changes in visual acuity and retinal thickness.
The observational design matters to interpretation. The record does not describe a randomized comparison, and it states that allocation was not stated. It also lists no control comparison that would permit a like-for-like assessment. An observed time to re-treatment in clinical practice can describe treatment patterns among the analyzed participants, but by itself cannot establish that treatment caused a particular timing pattern or that the pattern would differ under another treatment strategy.
The intervention wording also requires care. OZURDEX® appears in the arm description as a single dose that may be repeated in clinical practice, while the intervention listing says “No Intervention” and the description says no intervention was administered in the study. The registry does not clarify how those statements fit together. Accordingly, the record does not establish that treatment was assigned by the study or explain how clinicians decided on re-treatment.
For safety, the adverse-event record lists 99 participants at risk for serious events and 1 with a serious event. It lists 99 at risk for other events and 26 with other events. Endophthalmitis is listed as a serious adverse event term at 1.0%. These figures describe reported events in the registry; they do not establish that OZURDEX® caused an event, and the record does not supply a comparison group for interpreting risk differences. The death count is not reported in the registry record.
In sum, the registry record describes the question and planned summary but not the primary numerical result. It supports a description of the study's observational scope and the reported safety counts, but not a conclusion about the magnitude or precision of re-treatment timing, treatment effects, or comparative safety.
9. Statistical Methods Explained
Time-to-event analysis concerns the elapsed time until a defined event occurs. The endpoint is the time from the first OZURDEX® administration to the following administration in the study eye. The record expresses that time in days and gives 1 Year as the timeframe. The endpoint is therefore about when re-treatment occurred, rather than the size of a change in vision or retinal thickness.
What does the median represent?
The median is a measure of the center of a distribution. For a time-to-event outcome, it describes the time by which half of the observed event-time distribution lies on either side, when the median can be estimated. Unlike an arithmetic mean, the median is less influenced by a small number of unusually long or short times. It still does not describe every participant's experience or show the full spread of event times. The registry record identifies the median as the summary measure but does not report its value.
What does the confidence interval add?
A confidence interval communicates the uncertainty associated with an estimate under the statistical method used. It gives a range of values compatible with the observed data and analysis assumptions, rather than a guarantee that the true value lies within the interval. Its width is informative about precision: broader intervals indicate less precision, and narrower intervals indicate more precision. The record specifies a 95% Confidence Interval for the median, but the endpoints of that interval are not reported in the registry record. Without the estimate and interval, precision cannot be judged.
Why can incomplete follow-up matter?
Time-to-event studies may include participants whose event has not occurred by the end of their observed follow-up. Statistical methods can account for the fact that their event time is not known beyond the last observation; this is generally called censoring. The appropriate interpretation depends on how follow-up ends, whether event status is reliably recorded, and the assumptions used by the analysis. The primary population is described as all participants with complete data, but the registry does not report the number in that population, the amount or pattern of incomplete follow-up, or how participants without a recorded re-treatment were handled. No particular censoring method can therefore be attributed to this study from the registry record.
What would a hazard ratio mean?
A hazard ratio compares event rates at a given point in time between groups under a time-to-event model. It is not the same as a difference in median times, and it does not directly state how many days separate groups. The registry record does not identify a like-for-like control group or report a hazard-ratio estimate. A comparative hazard-ratio interpretation is therefore not supported by the outcome information recorded.
Why does the observational design matter?
In a randomized comparison, treatment assignment is determined by the study design. In an observational study, treatment and re-treatment decisions may occur as part of clinical practice. Differences in participant characteristics, clinical status, follow-up, or clinician decisions can be related both to treatment and to outcomes. Statistical adjustment can sometimes address measured differences, but it cannot automatically remove unmeasured confounding. The registry does not report an adjusted analysis plan or any outcome analyses. The observed timing, if reported, would consequently need to be read as descriptive of the analyzed clinical-practice cohort rather than as a randomized treatment effect.
How should planning illustrations be read?
Any sample-size figures associated with planning for a future comparison are illustrations, not observed power for this completed observational study. The stated illustration assumptions include a two-sided significance level of 0.05, equal allocation between two arms, a normal approximation, and an effect defined as a stated fraction of the observed effect. For time-to-event calculations, the stated quantity is the total number of events; for other calculations, it is participants per arm. Those assumptions describe a hypothetical planning exercise and do not establish that the original study was designed with those features. The study's own sample-size justification is not reported in the registry record. An illustration also cannot supply the absent primary outcome estimate or turn a nonrandomized study into a controlled comparison.
Finally, the registry lists 3 outcome measures and 0 analyses. The presence of named outcomes does not itself indicate that an analysis was completed or that estimates were posted. Interpretation of this record is therefore constrained by the missing outcome results and statistical details, not just by the general properties of time-to-event methods.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists 3 outcome measures: time to first re-treatment, change from baseline in best corrected visual acuity, and change from baseline in central retinal thickness measured by optical coherence tomography. It lists 0 analyses. The registry record does not report results for the primary or secondary outcomes, nor does it describe how the outcomes were analyzed or whether one outcome was treated as the principal basis for inference beyond its designation as primary.
When several outcomes are tested, the chance of at least one apparently notable result can increase if each is interpreted independently. Statistical plans may address this issue by defining a hierarchy, adjusting inference, or treating secondary outcomes as descriptive. No approach to multiplicity is reported in the registry record. It is therefore not possible to determine whether any multiplicity procedure was planned or applied.
The primary analysis population is described as all participants with complete data. The number meeting that description is not reported. The record does not explain how missing endpoint information was handled, whether participants with incomplete records were excluded, or whether any sensitivity analyses were conducted. It also does not report follow-up completeness or the amount of missing data for visual acuity and retinal thickness.
These omissions limit both reproducibility and interpretation. A complete-case population can differ from the enrolled population, and missing outcome information can affect estimated event timing or changes from baseline. Without the analysis population count, missing-data procedures, and outcome estimates, the extent and direction of any effect cannot be assessed. Interim-analysis plans and the detailed statistical analysis plan are also not reported in the registry record.
11. 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 |
|---|---|---|---|
| OZURDEX® | 1 | 99 | 1.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| OZURDEX® | 26 of 99 |
Most frequent serious adverse event terms
| Event term | Organ system | OZURDEX® |
|---|---|---|
| Endophthalmitis | Eye disorders | 1 of 99 |
Most frequent non-serious adverse event terms
| Event term | Organ system | OZURDEX® |
|---|---|---|
| Ocular hypertension | Eye disorders | 26 of 99 |
Serious events with the highest arm-level rate: endophthalmitis (1.0%).
The adverse-event record lists 99 participants at risk for serious adverse events, with 1 affected. It lists 99 participants at risk for other adverse events, with 26 affected. Endophthalmitis appears among the serious adverse event terms at 1.0%. These are registry-reported counts and a listed percentage; they should be read as descriptive entries, not as estimates of comparative risk.
The record does not provide a control group for safety comparison, event-level details, or a basis for attributing an event to the study drug. In particular, a reported event occurring during observation does not by itself establish causation. The registry's wording that no intervention was administered also sits alongside an arm description of OZURDEX® use in clinical practice, and the record does not explain how treatment exposure relates to adverse-event reporting.
The death count is not reported in the registry record. The listed at-risk counts should not be treated as the total enrollment or as a complete description of follow-up, because the record does not explain the safety analysis population or observation time for these counts. These safety figures therefore describe what was recorded, but do not support a conclusion about comparative safety or the cause of any event.
12. What the Result Does, and Does Not, Mean
The study addresses a practical descriptive question: when a participant in clinical practice received a first OZURDEX® administration, how long elapsed before the following administration in the study eye? The registry defines this interval and specifies a median with a 95% Confidence Interval over 1 Year. However, neither the median nor its confidence limits are reported. The record therefore does not reveal the observed re-treatment timing or its precision.
The observational setting is relevant to what the outcome could mean. Re-treatment timing may reflect clinical decisions made in practice as well as participant circumstances and follow-up. With no randomized comparison described and no allocation method stated, an outcome estimate would not, by itself, identify a causal effect of treatment. The record does not establish how clinicians made re-treatment decisions or whether every participant received the described treatment exposure.
The secondary outcomes could have provided information about changes in best corrected visual acuity and central retinal thickness. Their titles are recorded, but their estimates are not. The safety entries report serious and other adverse events and identify endophthalmitis as a serious term at 1.0%, but do not provide a comparative assessment or demonstrate causation.
Accordingly, the registry record establishes the study's stated purpose, design description, endpoint definition, and selected safety counts. It does not show whether the primary endpoint was met, quantify visual or anatomical changes, or demonstrate a treatment benefit or harm. It also does not establish how the registry's “No Intervention” designation relates to the arm description of OZURDEX® administration in clinical practice. Any conclusion beyond these recorded details would require outcome and methods details not reported in the registry record.
13. Why This Trial Matters Statistically
This study is statistically relevant because it asks a time-to-event question in routine clinical practice. The timing of a subsequent administration can describe how treatment decisions unfold over follow-up, which is distinct from measuring change in visual acuity or retinal thickness. The endpoint definition is specific about the starting administration, the subsequent event, the study eye, and the unit of time. That clarity helps identify the intended quantity even though its estimate is absent.
The registry also illustrates why the design and endpoint must be interpreted together. An observational record of re-treatment timing is not equivalent to a randomized comparison of treatment strategies. Clinical decisions may be associated with participant characteristics and follow-up, so an observed time does not isolate a treatment effect. The registry does not report a comparator, allocation method, or adjusted analysis that would support a causal interpretation.
Another statistical issue is the analysis population. The endpoint is defined for participants with complete data, while the record gives enrollment but not the complete-data count or the handling of incomplete follow-up. For time-to-event outcomes, those details affect how much information contributes to the estimate and how precisely it can be interpreted. The stated median and 95% Confidence Interval would ordinarily help convey the central timing and its uncertainty, but neither is posted.
Finally, the difference between the “No Intervention” listing and the OZURDEX® arm description makes transparent reporting especially important. Clarification of treatment exposure, re-treatment decisions, missing follow-up, and the analysis would help readers distinguish clinical practice patterns from study-assigned procedures. The registry record identifies a useful question but leaves those statistical details and the numerical outcome unreported.
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 limitations specific to this registry record constrain interpretation. First, the primary endpoint result is not reported: the median time to first re-treatment and its 95% Confidence Interval are absent. The number of participants with complete data and the number of re-treatment events are also not reported. The endpoint's precision and the amount of information supporting it therefore cannot be assessed.
Second, the study description and intervention fields are not fully consistent. The study is described as observational and the registry lists “No Intervention,” with a statement that no intervention was administered. The arm description nevertheless specifies OZURDEX® administration that may be repeated in clinical practice. The record does not clarify how participants' treatment was managed, whether exposure was assigned, or how re-treatment decisions were made.
Third, no randomized or like-for-like control comparison is identified, and allocation is not stated. The record does not provide an analysis plan, adjustments for differences among participants, or details of follow-up. Its observational design limits causal interpretation even if outcome estimates were available.
Fourth, the secondary outcome estimates are not reported, despite being listed. The record also does not describe missing-data methods, the handling of participants without a subsequent administration, multiplicity procedures, or interim analyses. The safety entries lack a comparative group and do not establish causation. Together, these omissions mean the registry record supports only a limited descriptive account of the study's stated aims and reported safety entries.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Post Market Surveillance of OZURDEX® for Branch Retinal Vein Occlusion (BRVO) and Central Retinal Vein Occlusion (CRVO) — NCT01568021.
- Registry record last updated 2015-02-10; status last verified 2015-01.
- Results first posted 2015-02-10.
- 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.
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18. Record Summary
The registry record describes a completed, multicenter observational study sponsored by Allergan, with enrollment of 100 participants. The study began in 2011-10 and reached primary completion in 2013-11. Its primary outcome is time to first re-treatment, defined as days between the first OZURDEX® administration and the following administration in the study eye, summarized by a median and 95% Confidence Interval over 1 Year.
The record lists secondary outcomes for change in best corrected visual acuity and central retinal thickness by optical coherence tomography, but does not report their results. It lists 3 outcome measures and 0 analyses. The primary estimate, its confidence interval, the complete-data population size, and missing-data methods are not reported in the registry record.
Safety entries list 1 serious event among 99 at risk and 26 with other events among 99 at risk; endophthalmitis is listed at 1.0%. The death count is not reported. The registry's intervention wording is unclear, and no like-for-like control comparison is described.