Endothelial Bleb Response With Toric Lenses: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Endothelial Bleb Response With Toric Lenses (NCT00630305), a randomized na study. The primary outcome is Endothelial Bleb Areas on Cornea: Session A- Open Eye.

2. Clinical Question

The study description distinguishes open-eye sessions, intended to simulate ordinary waking ocular behavior, from closed-eye sessions, intended to simulate ocular activity during periods when the eyes are closed, such as sleeping. The primary outcome title specifically identifies the open-eye Session A comparison. The broader record describes multiple sessions and testing scenarios, but it does not give the numerical results needed to quantify any difference in bleb area or its uncertainty.

3. Trial Design

The registry record identifies a randomized, single-masked, crossover study with an enrollment of 37. It lists the condition as ametropia and names three toric soft contact lens devices: alphafilcon A, lotrafilcon B, and senofilcon A. The official title describes an evaluation of short-term corneal endothelial response to toric soft contact lens wear in Asian eyes. The study is marked completed, with the recorded start in 2008-01 and primary completion in 2008-07.

The study used four sessions. According to the session descriptions, subjects were first randomized to a session and then randomized to receive one of four lens sequences for that session; each subject participated in all four sessions. Sessions A and B included senofilcon A and alphafilcon A, while Sessions C and D included senofilcon A and lotrafilcon B. The registry record does not explain how the four sequences were constructed, how the sequence order was implemented, or how much time separated sessions.

The crossover structure means that each subject participated in all four sessions, rather than being assigned to a single lens condition for the entire study. In general, crossover designs can compare conditions within the same subject, which may reduce the influence of stable differences between people. That advantage depends on suitable design and analysis; details such as carryover management and the statistical model are not reported in the registry record. Single masking is listed, but the identity of the masked party is not reported in the registry record.

The stated primary outcome concerns open-eye Session A and assessment 20 minutes after lens insertion. Other outcomes cover additional sessions and testing scenarios. The phase is listed as NA. The registry record does not report a sample-size justification, a detailed statistical plan, or the allocation sequence procedures.

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: Subjects were randomized to go to all four sessions (A, B, C and D) in a random order. Once in a session subjects were further randomized to one of four contralteral lens sequences (right eye / left eye).

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The analysis population consists of subjects that completed all study visits without a major protocol deviation. The analysis was conducted on subject eyes.

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.

Population: All participants who were enrolled and randomized to a trial arm.

6. Primary Endpoint

The registry lists the primary outcome as Endothelial Bleb Areas on Cornea: Session A- Open Eye, measured over 20 minutes post-lens insertion.

The primary outcome is titled “Endothelial Bleb Areas on Cornea: Session A- Open Eye.” It measures mean area of endothelial blebs in the central, nasal, temporal, inferior, and superior corneal locations. A masked observer selected a region in each image to balance maximum area with clarity of cell outlines, outlined blebs manually, and used software to calculate bleb area. The recorded unit is percent difference of bleb area, and the stated summary measure is the mean.

The comparison is described as the mean percent difference between senofilcon A, the test lens, and alphafilcon A, the control lens for Session A. Measurement occurred 20 minutes after lens insertion. The description says that results are reported according to the lens worn in the contralateral eye. This matters because the response in an eye may be considered in relation to the lens worn by the other eye, though the registry record does not provide further details about how that relationship was incorporated in the analysis.

Endothelial bleb formation is used in this study as an observed corneal response related to the investigation of oxygen deprivation during lens wear. As a general statistical point, a continuous area measure can describe both the direction and magnitude of a response, while a mean gives a summary across the observations included in an analysis. The registry record does not report the actual mean, its standard deviation, or a treatment-comparison estimate for this primary outcome. It therefore does not establish the size or precision of the observed difference.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record characterizes the primary outcome as the mean of a continuous measure. In general, a continuous endpoint can take a range of values rather than fitting into a small set of categories. Here, the measure is bleb area, and the stated unit is percent difference of bleb area. A mean is a summary of the central level of the observations included in the analysis. It does not, by itself, show how widely individual observations vary, which is why a measure of dispersion such as the standard deviation can also be informative. The record names the standard deviation as the dispersion measure, but does not report its value for the primary outcome.

The primary outcome description sets out an image-based measurement process: an observer selected a region, outlined blebs manually, and software calculated their area. The observer is described as masked. In general, masking can reduce the influence of knowledge about a condition on subjective choices during measurement. It cannot eliminate all measurement error, and the registry record does not report how observer agreement, image quality, or repeatability was evaluated.

There are several locations within the cornea: central, nasal, temporal, inferior, and superior. A result can be presented for each location or combined into a summary, but the registry record does not provide enough detail to determine how location-specific observations were summarized for the primary comparison. It describes mean area across the named locations and says results are reported for each testing scenario. It does not report whether the locations were analyzed separately, jointly, or through another method.

The crossover design means participants took part in multiple sessions. In general, a crossover analysis needs to recognize that observations from the same subject are related rather than independent. A suitable analysis may account for subject-level variation and for the conditions and periods in which measurements occurred. The registry record does not state which statistical model was used, whether the analysis included session or sequence terms, or how any possible carryover between sessions was addressed. These details should not be inferred from the design label alone.

The record lists randomized allocation and single masking. Randomization is generally used to reduce systematic differences in assignment, while masking can limit the effects of knowing a condition. The description says subjects were randomized to a session and then to one of four lens sequences for that session, and that each subject participated in all four sessions. It does not give the sequence-generation method, concealment procedures, or the identity of the masked party. Therefore, the labels do not establish exactly how those procedures were carried out.

A confidence interval is a general way to express uncertainty around an estimate. It gives a range of values compatible with the data and the method used, and its width reflects precision: narrower intervals indicate greater precision under that method. No confidence interval is reported for the primary outcome in the registry record. A p-value, when reported, addresses compatibility of data with a specified null model; it does not measure the size or practical importance of an effect. No primary-outcome p-value is reported either. Without an estimate and an uncertainty measure, the lens comparison cannot be evaluated for magnitude or precision.

The record’s sample-size assumptions describe a planning illustration using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is expressed as a stated fraction of the observed effect. These are planning assumptions, not a report of the trial’s original design justification and not observed power. The registry record does not report the original sample-size calculation, the assumptions used to plan enrollment, or a justification for the enrolled number. Any calculated sample size based on an observed effect would be illustrative, since it depends on the estimated effect and its assumptions rather than establishing what the completed study proved.

In general, over-dispersion occurs when the observed variability is greater than a model assumes. If a model understates variability, standard errors may be too small and uncertainty may appear narrower than warranted. This is a general statistical consideration, not a feature reported for this study. The primary measure is described as continuous, and no evidence about over-dispersion or model diagnostics is reported in the registry record.

The registry record lists zero analyses. That means no statistical analysis results are reported in the available record; it does not show that no analyses were conducted outside the registry. Nor does it identify an adjusted analysis, an unadjusted analysis, or a prespecified analysis plan. The record does not report model diagnostics, missing-data methods, or a procedure for handling multiple comparisons. Those absences limit interpretation rather than demonstrating that any particular method was or was not used.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists four outcome measures and describes multiple corneal locations, sessions, and open-eye and closed-eye testing scenarios. It also indicates that the primary outcome has several categories or time points and is not reduced to one comparison. When several outcomes, locations, or conditions are examined, the chance of finding an apparently notable result by chance can increase if many statistical tests are performed. As a general method, multiplicity procedures can address this concern, but the registry record does not report whether any such procedure was planned or applied.

The record lists zero analyses and gives no numerical result for the primary outcome. It does not report p-values, confidence intervals, an analysis hierarchy, or a distinction between confirmatory and exploratory comparisons. Consequently, the statistical handling of multiple outcomes and sessions is not reported in the registry record. The reader cannot determine which comparisons, if any, were formally tested or how a result would have been selected for emphasis.

The stated analysis population consists of subjects who completed all study visits without a major protocol deviation, and the analysis was conducted on subject eyes. This describes an eligibility rule for the analysis, but the number who met it is not reported in the registry record. The enrolled number is 37; the number who completed all visits, the number excluded for deviations, and the number of eyes included in each outcome analysis are not reported.

Missing observations can affect both the precision and potential representativeness of an analysis. In general, the implications depend on why measurements are missing and how the analysis handles them. The registry record does not report missing-data counts, reasons for missingness, imputation methods, or sensitivity analyses. It also does not provide enough information to assess whether the analyzed population differs from all enrolled participants. These gaps prevent evaluation of how incomplete visits or measurements may have influenced the reported estimates.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 5% reporting threshold.

The registry record lists four safety groups, one for each session. For Sessions A, B, C, and D, the number at risk for serious adverse events is 37 and the number affected is 0. The corresponding figures for other adverse events are also 37 at risk and 0 affected in each session. These entries describe the counts recorded for the session groups; they are not numerical results for the corneal bleb endpoint.

The deaths field is null for each group. A null entry is not the same as a reported count of zero, so deaths should be described as not reported in the registry record rather than as absent. The registry record also does not provide further information about how adverse events were defined, collected, or classified, or whether the same participants contributed to every safety group. It does state that each subject participated in all four sessions.

Zero affected participants in these entries means that no serious or other adverse events are listed as affecting participants in the respective groups. It does not, by itself, establish that no events occurred outside the recorded categories or reporting period. The record does not specify the observation duration for safety outcomes or give event-level descriptions. These safety counts should therefore be read narrowly as the figures recorded for the session groups, without drawing broader conclusions from them.

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

The registry record establishes that a randomized, single-masked crossover study was conducted to evaluate short-term corneal endothelial response to toric soft contact lens wear. It specifies the lens comparisons, four sessions, open-eye and closed-eye scenarios, the primary outcome definition, and the stated assessment time. It also records an enrollment of 37 and an analysis population definition based on completion of all visits without a major protocol deviation.

Those design details do not provide a numerical treatment comparison. The record does not report the primary outcome mean, its standard deviation, a confidence interval, or a test result. It is therefore not possible to say how large the bleb-area difference was, in which direction it went, or how precisely it was estimated. Nor can the absence of a reported result be interpreted as evidence that there was no difference.

In general, a statistical estimate describes the observed data under an analysis method; its uncertainty describes how much the estimate may vary under that method. A clinical interpretation may also require context about the size of a difference that would matter, the reliability of the measurement, and the relevance of the tested conditions. Such contextual thresholds are not reported in the registry record. No clinical threshold or claim about benefit or harm should be inferred from the study title or outcome description.

The safety entries report zero participants affected by serious and other adverse events in each session group, with 37 listed at risk in each. The deaths entries are null rather than reported as zero. These are safety-record entries and do not resolve the missing primary efficacy estimate. They should not be used to infer a general safety profile beyond the information recorded for this study.

Overall, the posted information allows readers to understand what was measured and how the study was structured, but does not support a quantitative conclusion about the primary comparison. The study’s completed status is not itself evidence for a particular result. Interpreting the findings would require the outcome estimates, uncertainty measures, and analysis details, which are not reported in the registry record.

13. Why This Trial Matters Statistically

This study is statistically interesting because it combines a crossover structure with measurements taken under different lens, session, and eye-state conditions. In a crossover design, the same participant contributes observations under multiple conditions. In general, that permits within-participant comparisons and can reduce the influence of characteristics that remain stable within a person. It also means that the analysis must account for the dependence among repeated observations rather than treating them as unrelated measurements.

The endpoint also illustrates how measurement procedures shape statistical evidence. Bleb area was assessed from images, with a masked observer selecting and outlining regions and software calculating area. Such a continuous measure can retain more information about magnitude than a simple present-or-absent classification, but it may depend on image selection and observer decisions. The registry record explains the process but does not report measurement repeatability or validation results.

The study’s multiple sessions and corneal locations highlight the importance of defining the primary comparison before examining results. Analyses across multiple conditions can address a broader scientific question, while also creating more opportunities for selective interpretation or chance findings if the analysis plan is unclear. The registry record does not report a statistical analysis plan, multiplicity procedure, or numerical results, so the reader cannot assess how these considerations were handled.

The record also demonstrates the difference between describing a design and reporting evidence. Enrollment, randomization, masking, and an outcome definition do not substitute for effect estimates and uncertainty. Without those results, the trial can be understood as a structured investigation of short-term response, but its reported statistical findings cannot be assessed. That distinction is useful whenever a registry entry contains detailed methods but no posted analysis.

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 principal limitation for statistical interpretation is that numerical results for the primary outcome are not reported in the registry record. No mean, standard deviation, effect estimate, confidence interval, or test result is available. As a result, the direction, magnitude, and precision of the comparison cannot be evaluated. The record lists zero analyses, which further means that no statistical analysis output is available in the record for interpretation.

The study includes several sessions, corneal locations, and open-eye and closed-eye scenarios, but the available description does not resolve these into a single reported comparison. It states that the primary outcome has several categories or time points and is not reduced to one comparison. Without numerical results and an analysis plan, it is unclear how the different measures relate to the primary question or how multiplicity was handled.

Although the study is identified as a crossover, the statistical model is not reported. The registry record does not describe how repeated observations within participants were accounted for, whether session or sequence effects were modeled, or whether carryover was considered. The sequence procedures and the identity of the masked party are also not reported in the registry record. These missing details limit evaluation of how the design was implemented and analyzed.

The analysis population is defined as subjects completing all study visits without a major protocol deviation, with analysis conducted on subject eyes. The number meeting that definition, the number of measurements available, the exclusions made, and the handling of missing data are not reported. The record also does not give a sample-size justification or explain whether the enrolled number was selected to achieve a planned precision or statistical objective.

Finally, the safety record gives session-level counts but does not report deaths as a numerical count, event definitions, or the safety observation period. These gaps do not establish that an adverse event occurred or was missed; they limit what can be concluded from the registry entry.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Endothelial Bleb Response With Toric Lenses — NCT00630305.
• Registry record last updated 2017-03-03; status last verified 2017-01.
• Results first posted 2017-03-03.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry record describes a completed, randomized, single-masked crossover study with 37 enrolled participants, evaluating short-term corneal endothelial response to toric soft contact lenses in Asian eyes. Each subject participated in four sessions. Sessions A and B compared senofilcon A with alphafilcon A; Sessions C and D compared senofilcon A with lotrafilcon B. The primary outcome named is bleb area in the open-eye Session A condition, assessed 20 minutes after lens insertion.

The outcome was based on image assessment across central, nasal, temporal, inferior, and superior corneal locations. The registry record lists four outcome measures but reports no numerical primary-outcome results and no statistical analyses. The analysis population was defined by study completion without major protocol deviation, but its size is not reported. Safety entries list zero serious and other adverse events affecting participants in each session group; deaths are not reported as a numerical count. The design and measurement question are described, but the size and precision of the primary comparison cannot be assessed from the posted results.