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 Study of CyPass Implantation In Patients With Open Angle Glaucoma Refractory to Single or Multi-agent Topical Therapy (NCT01166659), a na na study. The primary outcome is Proportion of Eyes With Intraocular Pressure (IOP) Reduction of ≥ 20% at 12 Months Postoperatively Who Were on Fewer or the Same Number of Ocular Hypotensive Medications as Compared With Baseline.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT01166659 |
| Phase | NA |
| Condition | Primary Open Angle Glaucoma (POAG) |
| Allocation | Not applicable (single group) |
| Design model | Single Group |
| Masking | None (open label) |
| Enrollment | 48 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Transcend Medical, Inc. |
| Results posted | Yes |
2. Clinical Question
Population
The study concerned patients with primary open angle glaucoma whose condition had not been adequately managed with at least one class of topical medical therapy. The primary endpoint population was eyes implanted with the CyPass 2FX device with data available. The registry record reports enrollment of 48, but it does not describe how enrollment maps to the number of eyes included in the endpoint population.
Intervention
The intervention was implantation of the CyPass Micro-Stent as a stand-alone therapy. The study purpose was to evaluate its safety and effectiveness for lowering intraocular pressure. The registry describes subjects as receiving the device; details about implantation procedures beyond that description are not reported in the registry record.
Comparator
This was a single-group study, not a randomized comparison. The registry record does not identify a concurrent control group or a separate comparison treatment. Baseline medication use is part of the primary endpoint definition, but it is not a randomized comparator and cannot isolate the effect of the device from other changes over time.
Primary question
Among eyes with available data, what proportion had an intraocular pressure reduction of at least 20% at Month 12 while using fewer or the same number of ocular hypotensive medications as at baseline? The primary endpoint combines pressure change with medication use. The registry record describes this question but does not report the proportion observed.
3. Trial Design
The registry record identifies NCT01166659 as a completed, single-group study of the CyPass Micro-Stent in patients with primary open angle glaucoma. The stated purpose was to evaluate safety and effectiveness as a stand-alone approach to lowering intraocular pressure in patients who had failed at least one class of topical medical therapy. The device is the listed intervention, and the arm description says subjects receive the CyPass Micro-Stent.
Enrollment is listed as 48. The study start is recorded as 2010-02, and primary completion as 2013-05. The phase is listed as NA. Allocation is also listed as NA, and masking is listed as NONE. These entries describe a design without a randomized allocation or masking designation; they do not establish that every aspect of study conduct was unmasked, because further procedural details are not reported in the registry record.
A single-group design can describe outcomes observed after implantation, but it does not provide a concurrent randomized control for estimating what would have happened under another treatment or no implantation. Baseline medication use serves as a reference within the endpoint definition, not as a separately assigned control condition. Changes from baseline may reflect the intervention, the natural course of disease, changes in care, measurement variation, or other influences that a single group cannot separate.
The primary endpoint is defined at Month 12 and concerns eyes with available data. Two secondary outcomes are listed: achievement of target intraocular pressure with and without ocular hypotensive medication, and the mean number of topical intraocular-pressure-lowering medications compared with baseline. The registry record does not report a detailed protocol, follow-up schedule beyond the stated endpoint timeframe, or the analysis plan for these outcomes.
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 reporting group includes all treated participants.
Overall Study
| Stage | CyPass Micro-Stent |
|---|---|
| STARTED | 48 |
| COMPLETED | 35 |
| NOT COMPLETED | 13 |
Reasons for not completing this period:
| Reason | CyPass Micro-Stent |
|---|---|
| Subject Decision | 8 |
| Investigator Decision | 2 |
| Death | 1 |
| Lost to Follow-up | 1 |
| Study Closed at Site | 1 |
Analysis population for the primary outcome, as defined in the registry: Eyes implanted with the CyPass 2FX device with data available.
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 | CyPass Micro-Stent |
|---|---|---|
| Participants analysed | 48 | |
| Age, Continuous | years | 68 (SD 10.96) |
| Sex: Female, Male: Female | Participants | 32 |
| Sex: Female, Male: Male | Participants | 16 |
| Region of Enrollment: Austria | participants | 4 |
| Region of Enrollment: Bulgaria | participants | 8 |
| Region of Enrollment: Germany | participants | 33 |
| Region of Enrollment: Spain | participants | 3 |
6. Primary Endpoint
The registry lists the primary outcome as Proportion of Eyes With Intraocular Pressure (IOP) Reduction of ≥ 20% at 12 Months Postoperatively Who Were on Fewer or the Same Number of Ocular Hypotensive Medications as Compared With Baseline, measured over Baseline; Month 12 postoperative.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | percentage of eyes |
| Endpoint classification | not reduced to a single comparison |
The primary endpoint is the proportion of eyes with an intraocular pressure reduction of at least 20% at Month 12 postoperative who were using fewer or the same number of ocular hypotensive medications as at baseline. It is defined for eyes implanted with the CyPass 2FX device that had data available. The registry describes intraocular pressure as fluid pressure inside the eye, measured using Goldmann applanation tonometry and reported in millimeters of mercury. A reduction from baseline is described as an improvement in pressure.
This endpoint combines two clinically distinct dimensions: pressure change and medication use. Requiring both conditions means that a qualifying eye must meet the pressure-reduction criterion while also not increasing its number of ocular hypotensive medications relative to baseline. Reporting a proportion can communicate how frequently the combined criterion was met among the eyes included in the analysis. It does not, by itself, describe the size of pressure changes among all eyes or the distribution of medication changes.
Such a composite criterion can be useful when the study question concerns pressure lowering alongside medication burden. Its interpretation depends on complete and consistent measurement of both components and on a clear definition of the analysis population. The registry record gives the endpoint definition and measurement approach, but it does not report the observed proportion, the number of eyes with available endpoint data, or an uncertainty interval. Therefore, the endpoint's observed value and precision cannot be assessed from the registry record.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry record establishes the study question and endpoint definition, but does not provide a numerical result for the primary endpoint. It therefore does not show what proportion of eyes met the combined criterion of an intraocular pressure reduction of at least 20% at Month 12 and use of fewer or the same number of ocular hypotensive medications as at baseline. No estimate of that proportion, confidence interval, or p-value is reported in the registry record. The record lists no analysis entries.
This distinction matters: a prespecified or registered outcome is not itself evidence of the outcome achieved. Without the observed endpoint result and the number of eyes contributing data, neither the magnitude of the result nor its statistical precision can be assessed. There is also no basis in the registry record for judging whether the result was consistent across participants or eyes, or whether it was sensitive to missing observations.
The single-group design constrains interpretation independently of whether outcome data are available elsewhere. A baseline comparison can indicate how measurements changed over time in the studied group, but it is not equivalent to a randomized comparison. Changes may be associated with implantation, but a single group cannot distinguish that association from time trends, concurrent care, regression to the mean, measurement variability, or other factors. This is a general limitation of uncontrolled before-and-after evidence, not a finding about what happened in this study.
The registry lists secondary outcomes concerning achievement of target pressure with and without ocular hypotensive medication, and the mean number of topical pressure-lowering medications compared with baseline. It does not report results for those outcomes in the record. The absence of posted results does not mean that an outcome was unchanged, that an analysis was not performed elsewhere, or that the intervention failed; it means the registry record does not permit those conclusions.
The safety entries report serious and other adverse-event counts for non-ocular and ocular categories. These are descriptive safety data, and their interpretation depends on the listed risk groups and event definitions. They do not establish a causal relationship between the device and every event. The record does not provide a randomized comparator with which to estimate excess risk, nor does it provide enough detail to resolve all differences between the adverse-event group denominators and the enrollment entry.
Overall, the posted record supports a description of the design, endpoint, and some adverse-event counts. It does not support a quantitative conclusion about the primary endpoint, its uncertainty, or comparative effectiveness. Any interpretation should keep the distinction between a defined study question and a reported study result explicit.
9. Statistical Methods Explained
Statistical methods determine how measurements are converted into estimates and how uncertainty is represented. For this study, the registry record gives the primary endpoint definition and the measurement approach, but does not report the statistical analysis plan or an endpoint analysis. The discussion below explains general concepts relevant to reading this type of endpoint; it does not claim that these methods were used in the study.
What does a proportion describe?
A proportion expresses how many observations meet a defined criterion relative to the observations eligible for that calculation. Here, the criterion is conjunctive: an eye must have an intraocular pressure reduction of at least 20% at Month 12 and use fewer or the same number of ocular hypotensive medications as at baseline. The denominator matters because the endpoint population is described as implanted eyes with data available. If eyes without Month 12 information are excluded, the resulting proportion describes the observed-data population rather than necessarily all eyes initially enrolled or implanted.
A proportion is an estimate, not a complete account of uncertainty. A confidence interval is a range calculated by a statistical method to express the uncertainty around an estimate under that method's assumptions. It can help readers distinguish a relatively precise estimate from one that is compatible with a broad range of underlying values. No confidence interval for the primary endpoint is reported in the registry record, so its precision cannot be evaluated.
Why combine pressure and medication use?
The endpoint pairs a pressure threshold with a medication-use condition. A combined endpoint can represent a study objective that values both a measured physiological change and the amount of medication used. However, it also means the proportion depends on both components being observed and satisfying their rules. An eye that meets the pressure criterion but does not meet the medication condition would not meet the combined endpoint, and vice versa. The registry record does not report separate primary analyses for these components or details about how medication counts were collected.
More generally, a threshold can make a result easier to interpret against a stated criterion, while discarding information about how close observations are to that threshold. Two eyes with different pressure changes may both fall on the same side of the endpoint threshold. Separate continuous summaries can preserve information about the distribution of pressure measurements, but the registry record does not provide such primary outcome summaries.
What can a single-group analysis establish?
In a single-group study, measurements before and after an intervention may be compared within the same group. Such a comparison describes change over time. It does not, by itself, estimate the causal effect of treatment because there is no randomized concurrent group showing the outcome that would have occurred under an alternative condition. Random allocation, when used, helps balance both measured and unmeasured influences on average. Without it, differences from baseline can have multiple explanations.
This is a general design principle, not a judgment about the quality of individual measurements. Even precise measurement cannot supply the missing counterfactual comparison. The registry record lists allocation as NA and the study model as single-group; a randomized treatment comparison is therefore not part of the design as recorded.
How should repeated eye measurements be considered?
The primary outcome is expressed as a percentage of eyes, while enrollment is reported for the study. In eye studies, the relationship between participant counts and eye counts can affect statistical analysis: observations from two eyes of one person may not be independent. Methods for clustered or paired data can account for such dependence when appropriate. The registry record does not report the number of eyes analyzed, whether one or both eyes per participant contributed, or whether any dependence adjustment was used. It is therefore not possible to assess how this issue was handled.
What analysis details are absent?
The registry record does not report an analysis method for the primary endpoint, a confidence interval, a p-value, or an estimate. It also does not report whether there were interim analyses, how the sample size was justified, or how multiplicity across outcomes was handled. These absences prevent readers from assessing whether the reported analysis, if conducted, followed a prespecified plan. They should not be replaced with assumptions about common practice.
In general, statistical significance and clinical importance are different concepts. A p-value, when reported, addresses compatibility between data and a specified statistical model under a null hypothesis; it is not a measure of effect size or proof of causation. A confidence interval communicates estimate precision under its assumptions, but does not remove design limitations. Because no primary numerical estimate or inferential result is reported in the registry record, neither statistical significance nor the magnitude and precision of the endpoint can be evaluated.
10. Multiplicity, Missing Data and Analysis Populations
The registry record lists a primary endpoint and two secondary outcomes. It does not report whether statistical testing was planned for these outcomes, whether a hierarchy or other multiplicity adjustment was specified, or how any conclusions would account for examining more than one outcome. When several outcomes are tested, the chance of at least one apparently notable result can increase; procedures for controlling that issue depend on the analysis plan. This is a general statistical consideration, not evidence that a particular procedure was used in this study.
Missing-data handling is also not reported in the registry record. The primary endpoint is defined for implanted eyes with data available, which indicates that the analysis population depends on data availability. The record does not state how many eyes had missing Month 12 measurements, why data might be missing, whether missing values were imputed, or whether sensitivity analyses were conducted. Without these details, readers cannot determine how missing observations affected the endpoint estimate.
The analysis population is not described beyond the endpoint's reference to eyes with available data. It is not reported whether the analysis included all implanted eyes, only eyes meeting particular follow-up conditions, or another defined population. The registry record also does not report a statistical analysis plan or interim-analysis details. These gaps limit assessment of prespecification and of the robustness of any estimate; no primary estimate is reported in the registry record to evaluate in any case.
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 |
|---|---|---|---|
| Non-Ocular Adverse Events | 2 | 48 | 4.2% |
| Ocular Adverse Events | 8 | 50 | 16.0% |
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 |
|---|---|
| Non-Ocular Adverse Events | 0 of 48 |
| Ocular Adverse Events | 36 of 50 |
Most frequent serious adverse event terms
| Event term | Organ system | Non-Ocular Adverse Events | Ocular Adverse Events |
|---|---|---|---|
| IOP above target | Investigations | 0 of 48 | 5 of 50 |
| Secondary surgical intervention | Injury, poisoning and procedural complications | 0 of 48 | 3 of 50 |
| Death | General disorders | 1 of 48 | 0 of 50 |
| Renal cancer | Neoplasms benign, malignant and unspecified (incl cysts and polyps) | 1 of 48 | 0 of 50 |
Most frequent non-serious adverse event terms
| Event term | Organ system | Non-Ocular Adverse Events | Ocular Adverse Events |
|---|---|---|---|
| Secondary surgical intervention: IOP management | Injury, poisoning and procedural complications | 0 of 48 | 13 of 50 |
| BCVA loss ≥ 2 lines at/after 3 months postoperatively | Eye disorders | 0 of 48 | 12 of 50 |
| Secondary surgical intervention: Cataract removal | Injury, poisoning and procedural complications | 0 of 48 | 11 of 50 |
| IOP ≥ 10 mmHg over baseline or > 30 mmHg at/after 1 month postoperatively | Investigations | 0 of 48 | 10 of 50 |
| CyPass device obstruction | Investigations | 0 of 48 | 6 of 50 |
| Secondary surgical intervention: CyPass obstruction lysis | Injury, poisoning and procedural complications | 0 of 48 | 5 of 50 |
| Hyphema | Eye disorders | 0 of 48 | 3 of 50 |
Serious events with the highest arm-level rate: iop above target (10.0%), secondary surgical intervention (6.0%), death (2.1%), renal cancer (2.1%).
The adverse-event record separates non-ocular and ocular categories and distinguishes serious from other adverse events. For non-ocular events, the at-risk group is listed as 48, with 2 serious events and 0 other events. For ocular events, the at-risk group is listed as 50, with 8 serious events and 36 other events. These are the registry's counts and denominators; they should be read as separate category entries, not combined into a single total.
The serious terms listed include IOP above target at 10.0%, secondary surgical intervention at 6.0%, death at 2.1%, and renal cancer at 2.1%. The record does not provide further detail in these entries about event timing, recurrence, severity criteria, or whether events were judged related to the device. The separate death fields for the adverse-event groups are null, while death also appears in the list of serious terms. The registry record does not explain this difference or provide enough information to reconcile the entries.
Adverse-event counts describe events recorded in the study; they do not by themselves establish that the intervention caused them. The group denominators differ between the non-ocular and ocular entries, and the record does not explain that difference. With no concurrent randomized comparator, these figures cannot quantify excess risk relative to another treatment. They should therefore be interpreted descriptively and with attention to the registry's category definitions and reporting limitations.
12. What the Result Does, and Does Not, Mean
The record establishes that a study was conducted to evaluate CyPass Micro-Stent implantation as stand-alone therapy in patients with primary open angle glaucoma who had failed at least one class of topical medical therapy. It defines a primary endpoint combining a pressure-reduction criterion with medication use at Month 12. It also records adverse-event counts in ocular and non-ocular categories. These are meaningful descriptions of the study question and recorded safety information, but they are not a complete report of the primary outcome.
No numerical primary endpoint result is reported in the registry record. Consequently, the record does not show whether the endpoint was met by any particular proportion of eyes, how precise an estimate might be, or how results varied across the endpoint population. It also does not report results for the listed secondary outcomes. The lack of posted outcome results should not be interpreted as evidence of either benefit or lack of benefit.
The single-group design also limits what change from baseline could establish. Without randomized concurrent allocation, observed change cannot be separated from other influences over time. This limitation remains even if an outcome estimate is available; it is especially important when interpreting a before-and-after endpoint as evidence about treatment effect.
The adverse-event entries can be read as recorded counts and listed serious-event terms, but not as proof of causation or comparative risk. The record does not report a control group, detailed event adjudication, or a reconciliation of the different at-risk counts. A balanced interpretation therefore separates what the record states from what it cannot establish: it documents a completed study, a defined endpoint, and descriptive safety entries, while leaving the primary outcome magnitude and comparative treatment effect unknown in the registry record.
13. Why This Trial Matters Statistically
This trial illustrates a common interpretive distinction in clinical research: a clearly defined outcome is not the same as a reported outcome. The registry specifies a threshold-based primary endpoint that requires both an intraocular pressure reduction and no increase in medication use relative to baseline. That definition makes the study question explicit, but without the observed proportion and its uncertainty, readers cannot judge the result's magnitude or precision.
The study also highlights the role of design in statistical interpretation. A single-group study can describe outcomes following an intervention and can document adverse events, but it does not create a randomized control condition. Baseline measurements provide a reference point, not a substitute for a concurrent comparison group. Statistical adjustment, if used, cannot automatically address unmeasured differences or establish the missing counterfactual.
For biostatisticians and clinical researchers, the record underscores the importance of transparent reporting beyond endpoint labels. Evaluation requires the number of observations contributing to each outcome, methods for missing data, the planned analysis population, uncertainty estimates, and a clear account of how outcomes were analyzed. The registry record does not report these details for the primary endpoint. Its adverse-event entries further show why denominators, event definitions, and reconciliation of category counts matter when safety data are read.
The statistical importance of this study record is therefore less about a quantified treatment effect than about recognizing what can and cannot be inferred from the available design and reporting. Readers can identify the intended outcome and study structure, but should not substitute design expectations or general conventions for unreported results and methods.
14. Limitations
- The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
- Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.
The registry record does not report the primary endpoint estimate, the number of eyes with available Month 12 data, or a confidence interval. These omissions prevent evaluation of the observed endpoint and its precision. Although the endpoint population is described as eyes implanted with the CyPass 2FX device with data available, the record does not give a detailed analysis-population definition or explain how missing observations were handled.
The study is recorded as single-group, with allocation listed as NA and masking as NONE. There is no randomized concurrent comparator in the recorded design. This limits causal interpretation of any change from baseline and prevents direct estimation of comparative effectiveness from the registry record. The record does not report whether other analyses attempted to address confounding.
Important statistical details are not reported in the registry record, including the analysis method, uncertainty estimation, sample-size justification, multiplicity handling, interim analyses, and the treatment of any dependence between eyes from the same participant. The record also does not clarify how the enrollment entry relates to the eye-based endpoint population.
Safety interpretation has additional constraints. The ocular and non-ocular adverse-event categories have different at-risk counts, and no explanation is reported. Death appears among the listed serious terms while the adverse-event death fields are null; the record does not reconcile those entries. Event timing, recurrence, attribution, and adjudication details are also not reported. These limitations do not establish that an event was or was not related to the device; they constrain what can be concluded from the posted record.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Study of CyPass Implantation In Patients With Open Angle Glaucoma Refractory to Single or Multi-agent Topical Therapy — NCT01166659.
- Registry record last updated 2017-05-15; status last verified 2016-10.
- Results first posted 2016-10-28.
- Data retrieved from ClinicalTrials.gov on 2026-11-09.
- Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.
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18. Record Summary
NCT01166659 is recorded as a completed, single-group study of CyPass Micro-Stent implantation in patients with primary open angle glaucoma who had failed at least one class of topical medical therapy. Enrollment is listed as 48; the study start is 2010-02, and primary completion is 2013-05. The primary endpoint concerns the proportion of eyes with at least a 20% intraocular pressure reduction at Month 12 and fewer or the same number of ocular hypotensive medications as at baseline.
The registry record does not report a numerical primary endpoint result or analysis entries. It lists secondary outcomes on target pressure and medication use, and it records ocular and non-ocular adverse-event counts. The single-group design and missing outcome and analysis details limit assessment of comparative effects, endpoint precision, missing-data impact, and safety attribution.