Retrospective Data Collection Study in Patients Receiving Two or More OZURDEX® Injections for Macular Oedema Secondary to Retinal Vein Occlusion: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Retrospective Data Collection Study in Patients Receiving Two or More OZURDEX® Injections for Macular Oedema Secondary to Retinal Vein Occlusion (NCT01566526), a registered phase not stated study. The primary outcome is Time to OZURDEX® Re-Injection in the Study Eye.

2. Clinical Question

The study also set out to examine visual acuity, retinal thickness and the timing of visual improvement. These secondary outcomes concern changes in best corrected visual acuity (BCVA), the percentage of patients reaching specified line improvements, central retinal thickness measured by optical coherence tomography (OCT), and time to visual improvement.

The central question is descriptive: it concerns injection timing among people who had already received repeated treatment in routine practice. It is not a randomized test of OZURDEX® against another treatment or against no treatment. The registry record does not report numerical results for the primary outcome or the listed secondary outcomes, so the size and precision of any observed changes cannot be assessed from this record.

3. Trial Design

This is a completed retrospective data collection study sponsored by Allergan. The registry record gives a study start of 2012-03 and a primary completion date of 2012-06. It lists 26 enrolled patients with retinal vein occlusion and macular oedema. The study population is described as patients previously treated with OZURDEX® through the Belgium Medical Needs Program.

The intervention is dexamethasone intravitreal implant 0.7 mg. The arm description says OZURDEX® was administered at least twice in accordance with routine clinical practice. The record does not describe a randomized allocation or a control arm. It therefore does not present a treatment-versus-control design; comparisons between the described patients and an external or untreated group are not available in the record.

The primary outcome is time to OZURDEX® re-injection in the study eye. Its measurement begins at the first OZURDEX® injection and ends at the second, with a stated timeframe of up to 12 months. The outcome is specified as a mean and standard deviation, and the stated population is all enrolled patients.

Seven outcome measures are listed in total: the primary measure and secondary measures concerning BCVA, central retinal thickness by OCT, and time to visual improvement. The registry record lists zero analyses. It does not report the numerical results for these measures, the statistical analysis details used for the retrospective data, or the approach to incomplete records. Those omissions limit assessment of how the planned outcomes were summarized and how much information contributed to each result.

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

Analysis population for the primary outcome, as defined in the registry: All enrolled patients.

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 Time to OZURDEX® Re-Injection in the Study Eye, measured over Up to 12 Months.

The primary endpoint is the time to OZURDEX® re-injection in the study eye, measured in days from the first injection to the second. The registry record specifies a mean and standard deviation and identifies all enrolled patients as the outcome population. Its timeframe is up to 12 months.

This endpoint describes the interval between two treatment events in the routine-practice setting represented by the study. A mean gives a measure of the group’s average interval, while the standard deviation describes the spread of individual intervals around that average. These are different aspects of the distribution: an average alone would not show whether patients’ intervals were similar or widely dispersed.

Injection timing is relevant to the study’s stated aim of evaluating the re-injection interval alongside efficacy and safety. However, an interval is not itself a measure of visual benefit or retinal thickness. It describes when a subsequent injection occurred, not why that timing was chosen or what clinical factors influenced it. The registry record does not report a numerical mean, standard deviation, or other result for this endpoint. Consequently, the distribution of intervals and the precision of its estimated average cannot be evaluated from the record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record specifies the primary endpoint as a continuous measure summarized by a mean and standard deviation. The mean describes the central value of the observed injection intervals. The standard deviation describes how much individual intervals vary around that mean. In general, these statistics are most informative when read together: two groups or samples can have the same mean but markedly different spread. No numerical primary estimate or standard deviation is reported in the registry record, so neither can be interpreted for this study.

What does a confidence interval add?

In general, a confidence interval expresses uncertainty around an estimated quantity. It gives a range of values compatible with the observed data under the statistical method used. A narrow interval indicates greater precision than a wide interval, but it does not eliminate limitations in study design, data collection, or representativeness. The registry record does not report a confidence interval for the primary endpoint or the listed secondary outcomes.

How should a retrospective estimate be understood?

In general, retrospective studies analyze information collected before the study question is addressed. This can allow description of routine-practice experience, but the available records and treatment decisions were not necessarily created under a common research protocol. Differences in follow-up, documentation, patient circumstances, and clinical decisions can affect what is observed. These are general considerations; the registry record does not detail how each was handled in this study.

The record says OZURDEX® was administered at least twice in accordance with routine clinical practice. The primary measure begins with the first injection and ends with the second. It therefore describes the interval among the treatment events included in the study, not an assigned interval imposed by a randomized schedule. The record does not report a comparison group or a statistical adjustment strategy.

What do the visual outcomes represent?

BCVA is best corrected visual acuity. The listed outcomes include change from baseline, the percentage with an increase of 2 lines or more, the percentage with an increase of 3 lines or more, and time to those improvements. These outcomes describe different features: a change score summarizes movement from baseline, a threshold percentage counts patients meeting a defined improvement criterion, and a time-to-improvement measure concerns when a threshold is reached. The record does not give the numerical results or detailed methods for calculating these measures.

Central retinal thickness measured by OCT is another listed outcome. In general, OCT provides imaging from which retinal thickness can be assessed. The registry identifies a change from baseline in the study eye, measured 7 to 12 weeks following the last injection. No result is reported, and the record does not give details about image grading, measurement variability, or handling of unavailable scans.

Why can variability matter?

In general, measures with greater variability are harder to estimate precisely, especially when the amount of available information is limited. For count or rate outcomes, over-dispersion means that variation exceeds what a simple model assumes; ignoring it can make uncertainty appear too small. The primary endpoint is specified as a continuous mean, and the record does not report an over-dispersion analysis or a model for the secondary outcomes. These general concepts should not be mistaken for methods documented in the registry.

The record also describes planning illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation, and a normal approximation. It states that time-to-event illustrations use a total number of events under the Schoenfeld approach, whereas other illustrations give participants per arm. Such calculations are planning illustrations, not observed power and not evidence that the study was designed with those assumptions. The record does not provide numerical illustration results in the registry record for this description. Since this study has no stated two-arm randomized comparison, an equal-allocation planning scenario should not be interpreted as the actual design.

Finally, the registry lists zero analyses and does not report a statistical analysis plan. The specific methods used to estimate the primary mean, handle incomplete observations, or analyze secondary outcomes are not reported in the registry record. General statistical principles can clarify what estimates and uncertainty measures mean, but they cannot fill in unreported methods or results.

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.

R code and output

arm <- c("Patients Previously Treated With OZURDEX®")
n   <- c(26)
m   <- c(143.65)
sp  <- c(42.95)
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  Patients Previously Treated With OZURDEX®  26  143.650  42.950  126.302  160.998

11. Multiplicity, Missing Data and Analysis Populations

The registry lists seven outcome measures: one primary outcome and six secondary outcomes. The secondary measures cover several related but distinct questions about BCVA, retinal thickness, and timing of visual improvement. When multiple outcomes are examined, the chance of at least one apparently notable result can increase if each is tested separately. General approaches to multiplicity include prespecifying a primary comparison, adjusting significance thresholds, or treating secondary findings as exploratory. The registry record does not report a multiplicity strategy, so it is not possible to say whether or how this issue was addressed.

The record identifies all enrolled patients as the population for the primary endpoint, but it does not give the number with evaluable data for that endpoint or for each secondary measure. It does not describe missing-data definitions, reasons for missingness, exclusions, imputation, or sensitivity analyses. The absence of these details means the extent and possible influence of incomplete outcome information are not reported in the registry record.

The registry lists zero analyses. It does not provide outcome estimates, uncertainty intervals, or a statistical analysis plan. It also does not specify the analysis populations used for the BCVA, OCT, or time-to-improvement outcomes. Accordingly, readers cannot determine from this record whether every listed outcome was analyzed, how baseline values were incorporated, or how repeated measurements and timing were handled. These are limits of what the registry record documents, not proof that particular procedures were or were not used outside the record.

12. 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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry record lists 26 patients at risk for serious adverse events and 0 affected. It also lists 26 at risk for other adverse events, with 20 affected. These are counts reported for the group previously treated with OZURDEX®; they are not a comparison between treatment arms.

The record does not identify the specific non-serious events, their severity, duration, timing, or whether an event was considered related to treatment. No serious adverse event terms are listed. Deaths are not reported in the registry record. Consequently, the counts give only a limited view of the safety information recorded and do not describe the clinical details behind the events.

A count of zero serious adverse events in this record should be read as the reported observation for this study group, not as proof that serious events cannot occur. In general, the ability to characterize uncommon events depends on the amount and completeness of safety information and on the study design. The registry record does not report further safety analyses or the methods used to collect and classify adverse events.

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

This record describes a retrospective study of patients who received at least two OZURDEX® injections for macular oedema secondary to retinal vein occlusion through the Belgium Medical Needs Program. Its primary question concerns the interval from the first injection to the second in the study eye. It also lists visual acuity, retinal thickness, and time-to-improvement outcomes.

The record does not report numerical results for the primary endpoint or any of the secondary outcomes. It therefore cannot establish the observed average re-injection interval, the variability in that interval, the extent of any visual acuity or retinal thickness changes, or the precision of those estimates. Completion status indicates that the study is marked completed; it does not substitute for outcome results.

The design is descriptive and retrospective, with no comparator group stated. As a result, observations from this group cannot by themselves identify what would have happened under a different treatment or establish a causal treatment effect. Routine-practice injection timing may reflect clinical circumstances that the record does not describe. The study also cannot be read as a randomized comparison.

The safety record reports no serious adverse events among those at risk and reports other adverse events among some patients, but it does not provide event terms or additional detail. These counts should not be extended beyond the categories and group represented in the registry.

In general, a clinical study’s interpretation depends on its design, outcome definitions, results, and uncertainty. Here, the outcome definitions and broad study context are recorded, but numerical outcome estimates and analysis details are not. The record is therefore useful for understanding the question and study structure, while its documented information is insufficient to quantify the primary or secondary outcomes.

14. Why This Trial Matters Statistically

This study raises a practical statistical question: how to describe the interval between repeated injections when treatment is delivered in routine practice. Such a measure is not simply a treatment effect. It is an observed interval that can reflect clinical decision-making and the circumstances of the patients whose records were collected. Clear endpoint definitions matter because the interval’s starting and ending events determine what the estimate means.

The registry specifies the first-to-second injection interval in the study eye and identifies a mean and standard deviation as its summary. That pairing is statistically useful in principle: the mean describes the average interval, while the standard deviation conveys how much intervals vary. Yet the record does not include the numerical estimate or its variability. This illustrates why an outcome definition alone is not enough for interpretation; reported results and measures of uncertainty are also needed.

The design also demonstrates the distinction between descriptive evidence and comparative evidence. A single previously treated group can describe what was recorded for those patients, but without a stated comparator it cannot establish how the observations differ from an alternative treatment strategy. Retrospective collection adds a further need for transparency about data completeness and analysis choices, details that are not reported in the registry record.

Finally, the study lists multiple outcomes spanning visual function, retinal structure, and timing. Those domains address different aspects of the clinical question, but multiple outcomes make prespecification and transparent reporting important. The record identifies the outcomes but does not report their numerical results or a multiplicity approach. Statistically, the study is most informative as a record of the questions posed and the limits of what is documented—not as a basis for estimating treatment effects from unreported results.

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.

The principal limitation for interpreting the record is that numerical results are not reported for the primary endpoint or the listed secondary outcomes. Although the primary measure is defined as a mean and standard deviation, neither value is recorded. No confidence intervals or other uncertainty estimates are reported, so precision cannot be assessed.

The study is retrospective and has no comparator group stated. The record describes treatment in routine clinical practice, but it does not report the clinical factors governing injection timing or other potential influences on the observations. As a result, the interval cannot be interpreted as a controlled treatment schedule or a causal effect.

The record does not describe missing-data handling, the number of evaluable observations for each endpoint, or analysis populations for the secondary outcomes. It also does not report detailed statistical methods, including any adjustment for multiple outcomes. These omissions prevent assessment of whether the analyses addressed incomplete records or the range of outcomes consistently.

Safety reporting is also limited: event terms are not listed, deaths are not reported, and details about timing, severity, and attribution are absent. The recorded adverse-event counts should therefore be understood narrowly, rather than as a comprehensive characterization of safety.

The registry lists 26 enrolled patients, but the record does not provide numerical outcome results with which to judge the information available for each endpoint. General limitations of retrospective data collection may apply, but the specific extent of any documentation or follow-up issues is not reported in the registry record.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Retrospective Data Collection Study in Patients Receiving Two or More OZURDEX® Injections for Macular Oedema Secondary to Retinal Vein Occlusion — NCT01566526.
• Registry record last updated 2013-05-27; status last verified 2013-03.
• Results first posted 2013-05-27.
• 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.

19. Record Summary

This completed retrospective data collection study, sponsored by Allergan, concerns OZURDEX® use for macular oedema secondary to retinal vein occlusion. It lists 26 enrolled patients previously treated at least twice in routine clinical practice through the Belgium Medical Needs Program. The study start is recorded as 2012-03 and primary completion as 2012-06.

The primary outcome is the mean time in days from the first to the second OZURDEX® injection in the study eye, over a timeframe of up to 12 months. Secondary outcomes address BCVA, central retinal thickness by OCT, and time to visual improvement. Numerical results and analysis details are not reported in the registry record.

The record lists 0 serious adverse events among 26 at risk and other adverse events affecting 20 of 26 at risk. Event details are not reported, and deaths are not reported in the registry record. No comparator group is stated.