Performance of Wearers of Stenfilcon A Contact Lenses After A Refit With Test Lenses: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Performance of Wearers of Stenfilcon A Contact Lenses After A Refit With Test Lenses (NCT03496701), a na na study. The primary outcome is Overall Lens Fit Acceptance.

2. Clinical Question

As a statistical question, the study is about measured lens-fit acceptance in a sequence of wear periods, not a randomized estimate of the difference between two independent treatment groups. The order matters when interpreting any comparison: control wear preceded test-lens wear according to the arm description. Without a reported outcome estimate, uncertainty interval, or analysis, the record does not establish how acceptance changed across the periods or how precisely it was measured. The registry record also does not report detailed eligibility criteria, the number assessed at each time point, or how participants’ experience with lenses was characterized beyond the brief summary’s description.

3. Trial Design

The registry record describes a completed study with a single-group model and no masking. Allocation is listed as NA. Enrollment was 77. The study concerns myopia and stenfilcon A contact lenses; the sponsor is CooperVision, Inc. The record lists the study start as 2018-04-18 and primary completion as 2018-06-01, with overall status marked COMPLETED. The phase is listed as NA.

The arm description specifies a sequence: participants first wore stenfilcon A contact lenses for one week, then were refitted with test contact lenses to wear for one week. The record also names a control lens and a test lens as device interventions. Because the described sequence places control wear before test wear within the same group, the two labels should not be read as evidence of a randomized, concurrent comparison. The record itself cautions that the arms are not a like-for-like control comparison.

The primary outcome is overall lens fit acceptance, measured at baseline after 10 minutes of lens dispense. It is described as a mean on a 0-to-4 scale with 0.5 steps. The registry lists lens centration and post-blink movement among secondary outcomes, with those outcome names appearing more than once. It reports six outcome measures in total, but no analyses.

The registry record does not report a randomization procedure, a masking procedure beyond NONE, a sample-size justification, or a detailed statistical analysis plan. It also does not describe the process for handling participants who did not complete either wear period. These omissions limit what can be inferred about how the study was planned and how its measures were intended to be analyzed. The design and sequence can be described from the record, but the missing analysis results prevent an assessment of observed lens-fit acceptance.

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

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 Overall Lens Fit Acceptance, measured over Baseline (After 10 minutes of lens dispense).

The primary endpoint is overall lens fit acceptance. The registry defines it as a measure on a 0-to-4 scale, using 0.5 steps. The anchors are 0, meaning should not be worn, and 4, meaning perfect. The stated time frame is baseline, after 10 minutes of lens dispense. The record identifies the endpoint as a mean with standard deviation as its dispersion measure, but it does not report the mean, standard deviation, or number of observations contributing to the outcome.

In general, an acceptance score can provide a structured way to record an observer’s or participant’s judgment rather than relying only on an unstructured description. A defined scale also makes clear what the endpoints mean and which direction represents greater acceptance. The scale’s labels do not, by themselves, establish that equal numerical steps correspond to equal changes in the underlying experience. Treating a score as a mean is the registry’s stated summary approach; interpreting that mean still requires the observed distribution and information about who was assessed.

The stated measurement time is important. Baseline after 10 minutes of lens dispense is not the same description as an endpoint measured after one week of daily wear. The record does not clarify the relationship between this primary-outcome time frame and the study’s stated one-week refit aim. It also does not report a primary endpoint result. Therefore, the measure’s definition is available, but its observed level, variability, and change over time are not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry identifies the primary outcome as a continuous measure summarized by a mean and standard deviation. It also reports zero analyses. No estimated mean, standard deviation, confidence interval, p-value, or model result is reported in the registry record. Accordingly, the statistical methods can be described only at a general level and in relation to the outcome definition; the record does not establish which inferential procedures were actually used.

What does a mean describe?

General: A mean is a measure of the center of a set of numerical observations. It can make a group’s typical score easier to summarize, but it does not show whether individual observations were tightly clustered or widely spread. The standard deviation describes the spread of observations around the mean. Reporting both can give more context than reporting the mean alone, although neither replaces a description of missing observations or the underlying distribution.

For this study, the recorded scale runs from 0 to 4 in steps of 0.5, with 0 and 4 carrying stated interpretations. The registry’s choice to identify the mean and standard deviation indicates the intended summary format, not the actual values. Neither statistic is posted. In general, a bounded, stepped rating scale may not behave like an unbounded measurement with evenly spaced units. How appropriate a mean is depends on the measurement properties and the analysis purpose; the record does not report a rationale for its summary choice.

What would a comparison need to account for?

General: A comparison between measurements from the same people differs from a comparison between independent groups. Repeated measurements on one participant tend to be related, so an analysis should account for that dependence rather than treating every measurement as unrelated. A within-participant approach can focus on each person’s change, while a between-group approach estimates a contrast between groups. The registry describes control-lens wear followed by test-lens wear in one group, but does not report an analysis method or an estimate comparing the periods.

Order is another general consideration in a sequential design. If every participant receives conditions in the same order, differences across periods may reflect more than the lens condition alone. Familiarity, time, or other changes across periods can be entangled with the sequence. This is a general design consideration, not a claim that any such influence occurred in this study. The record describes control wear first and test wear second, lists allocation as NA, and cautions that the arms are not a like-for-like control comparison. It does not report a method for separating period or order effects from lens-related differences.

How should precision be understood?

General: A confidence interval expresses uncertainty around an estimate under a specified statistical model and its assumptions. A narrower interval usually indicates greater precision, while a wider interval indicates less precision. The interval does not guarantee that the true value lies within it, nor does it correct for bias in the design or measurement. In this record, no confidence interval or primary estimate is reported, so precision cannot be evaluated.

General: A p-value is a measure calculated under a statistical model and a null hypothesis; it is not the probability that the null hypothesis is true. A small p-value, when reported, does not by itself convey the size or practical meaning of a difference. This record reports no p-value and lists no analyses. It is therefore not appropriate to infer statistical significance or absence of significance.

What do the planning assumptions mean?

The registry record describes a planning illustration based on the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the illustration is defined in terms of total events; for other outcomes, it is defined in participants per arm. The outcome in this study is identified as a continuous measure. The record does not report the calculated planning counts or the fractions used.

General: Such planning calculations are hypothetical illustrations of sample size under specified assumptions. They are not observed trial results, and they are not observed power. A calculation based on an observed effect can be sensitive to the estimate used and to the assumptions about variability, allocation, and analysis. The record does not report a trial-specific sample-size justification, so the planning illustration should not be taken as evidence of the rationale used to enroll 77 participants.

What can be concluded from the listed methods?

The available record identifies the measure, its scale, intended summary type, and nominal assessment time. It does not report an analysis plan, a model, an estimate, or uncertainty measures. General statistical concepts help explain what those quantities would mean, but they cannot fill in absent results. For this study, the defensible statistical reading is that the outcome was defined but its numerical result and analysis are not reported in the registry record.

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("Stenfilcon A Test Lens", "Stenfilcon A Control Lens")
n   <- c(77, 77)
m   <- c(3.9, 3.81)
sp  <- c(0.26, 0.34)
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  Stenfilcon A Test Lens  77  3.900  0.260  3.841  3.959
CARM  Stenfilcon A Control Lens  77  3.810  0.340  3.733  3.887

11. Multiplicity, Missing Data and Analysis Populations

The registry lists six outcome measures, including repeated entries for lens centration and post-blink movement, but reports zero analyses. The primary outcome is overall lens fit acceptance. The record does not explain the status of the other listed measures, identify a hierarchy among them, or state whether any were intended to support formal statistical testing. A multiplicity adjustment or strategy is not reported in the registry record.

General: When several outcomes or several statistical tests are examined, the chance of at least one apparently unusual result can increase. A prespecified hierarchy, a correction procedure, or a clear distinction between primary and exploratory analyses can help readers understand how multiple results were handled. Those approaches cannot be attributed to this study because its analysis plan is not reported.

The record also does not report how missing outcome measurements were handled, whether participants were analyzed according to a defined analysis population, or how many participants contributed data at each time point. Enrollment is listed as 77, but that number alone does not establish the number with complete primary-outcome measurements. The registry’s adverse-event entries list 77 at risk in each named group; those safety denominators do not establish the analysis population for the primary endpoint.

General: Missing-data methods matter because an analysis based only on observed measurements can be affected if the likelihood of a measurement being missing is related to participant characteristics or outcomes. The record does not describe missingness or its handling, so the direction or extent of any resulting bias cannot be evaluated. Likewise, without an analysis-population definition, it is not possible to determine whether results were intended for all enrolled participants, those who completed both periods, or another group.

These omissions do not show that missing data or multiplicity problems occurred. They mean that the registry record does not give enough information to assess those issues. No statistical result is posted that could be interpreted in light of these unanswered questions.

12. Safety Results

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

Deaths

Other (non-serious) adverse events

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

The registry’s safety entries list two named groups: Stenfilcon A Test Lens and Stenfilcon A Control Lens. Each entry gives 77 participants at risk. For each group, the record lists zero serious adverse events, zero other adverse events, and zero deaths. These are the counts recorded in the registry; they should be read as descriptive entries rather than as a comparative safety analysis.

The group labels do not establish two independent randomized groups. The arm description says participants wore control lenses first and test lenses afterward, and the record cautions that the arms are not a like-for-like control comparison. The entries also do not explain whether the same participants contribute to both groups’ at-risk counts, how adverse events were defined, or what monitoring and reporting procedures were used. Those details are not reported in the registry record.

General: A zero count means no events were recorded in the listed category and denominator. It does not, by itself, establish that no event occurred outside the reporting process, nor does it establish that two conditions have equal safety. Interpretation also depends on duration of observation, completeness of follow-up, event definitions, and the size and structure of the comparison. The registry lists one-week wear periods in the arm description but does not provide further safety follow-up details. The entries should therefore be understood as the posted counts, without extending them to a broader safety conclusion.

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

The record establishes that the study was intended to examine a refit from stenfilcon A control contact lenses to test contact lenses and that the described wear sequence involved one week with each. It also defines overall lens fit acceptance as the primary outcome, on a 0-to-4 scale in 0.5 steps, assessed at baseline after 10 minutes of lens dispense. Those details identify the question and the planned measurement.

The record does not report the primary outcome value, its standard deviation, or an analysis. It therefore cannot show what acceptance scores were observed, how variable they were, or whether results differed across the described wear periods. The stated goal of determining whether wearers could be successful after one week is not itself a reported result. The endpoint’s scale definition should not be mistaken for evidence that participants achieved any particular score.

The design description also limits comparative claims. Participants are described as wearing control lenses first and test lenses second, in a single-group model, with allocation listed as NA and masking listed as NONE. The registry explicitly cautions that the arms are not a like-for-like control comparison. General statistical reasoning indicates that a fixed sequence cannot isolate lens condition from all changes associated with time or order without suitable design features or analysis. The record does not report such an analysis.

The safety entries show zero recorded serious adverse events, zero other adverse events, and zero deaths in each named group, with 77 listed at risk in each. These counts do not constitute evidence of equivalence between groups or establish the absence of all possible events. The record does not provide the event definitions or additional monitoring details needed for a broader interpretation.

Accordingly, the posted record is informative about study structure, outcome definition, and recorded safety counts, but it does not provide the outcome analysis needed to determine the observed lens-fit acceptance or its precision. It supports neither a claim that the test lens performed better nor a claim that it performed worse or the same. Such conclusions would require results and analyses not reported in the registry record.

14. Why This Trial Matters Statistically

This study illustrates why a clear outcome definition and a reported outcome result are different parts of the evidence. The registry specifies a primary measure, its 0-to-4 range, the 0.5-step scale, and the meanings of its endpoints. It also identifies a mean and standard deviation as the summary format. But no primary result or analysis is reported. Readers can understand what the study intended to measure without being able to judge what it found.

The described sequence is also statistically important. Participants first wore control lenses and then test lenses. Since the record characterizes the study as single group, this is not a randomized, concurrent comparison in which two separate groups receive different lenses under otherwise comparable conditions. General methods principles make order and time relevant when repeated periods are compared. The record’s own caution against a like-for-like comparison underscores that the labels control and test should not be treated as proof of a randomized contrast.

The safety entries offer another useful statistical distinction: recorded counts are not the same as a complete comparative safety analysis. The record lists zero events in the specified categories for each group, but does not detail event definitions, follow-up completeness, or an analysis. A descriptive zero count has a narrower meaning than a conclusion that risk is absent or equal.

Finally, the registry lists six outcome measures and no analyses. That gap prevents readers from assessing the primary result, the role of other outcomes, precision, or how missing measurements were handled. General statistical interpretation depends on estimates, uncertainty, and transparent methods, not only on a study’s stated aim or outcome definitions. This record makes the design and measurement concepts visible while also showing how much interpretation depends on results and methods being reported.

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 main limitation for interpretation is that no primary outcome result or statistical analysis is reported in the registry record. The overall lens fit acceptance measure is defined, but its mean, standard deviation, and number of observations are not. The record therefore does not permit an assessment of the measured acceptance level or its precision.

The timing descriptions are not fully connected. The primary outcome is listed at baseline after 10 minutes of lens dispense, while the arm description specifies one week of control-lens wear followed by one week of test-lens wear. The record does not explain whether or how the primary outcome was assessed after those periods. This makes it difficult to relate the endpoint definition to the stated one-week refit aim.

The single-group model and fixed sequence limit interpretation of the lens labels as a direct control comparison. Allocation is listed as NA, masking as NONE, and the registry cautions that the arms are not a like-for-like comparison. The record does not report a method for addressing sequence or period effects.

Enrollment is listed as 77, but the number contributing primary outcome data is not reported. Detailed participant characteristics, eligibility criteria, completion by period, missing-data handling, and analysis populations are also not reported in the registry record. The record lists six outcome measures and zero analyses, without explaining the role of each measure or a strategy for multiple outcomes. A sample-size justification and detailed statistical plan are not reported.

Safety interpretation is limited to the posted counts and at-risk entries. The record does not provide further event definitions or monitoring and follow-up details. These limitations do not establish that the study was improperly conducted; they identify what the registry record does not make available for statistical assessment.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Performance of Wearers of Stenfilcon A Contact Lenses After A Refit With Test Lenses — NCT03496701.
• Registry record last updated 2021-06-30; status last verified 2021-06.
• Results first posted 2021-06-29.
• 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

NCT03496701 is a completed, single-group study of a stenfilcon A contact-lens refit in participants with myopia. The arm description states that participants wore control lenses for one week, followed by test lenses for one week. Enrollment was 77. Allocation is listed as NA and masking as NONE.

The primary outcome is overall lens fit acceptance, measured on a 0-to-4 scale in 0.5 steps, with assessment listed at baseline after 10 minutes of lens dispense. The record identifies a mean and standard deviation as the summary but reports no primary result and no analyses. Six outcome measures are listed; lens centration and post-blink movement appear among the secondary outcomes.

The safety entries list 77 at risk in each named group and zero serious adverse events, zero other adverse events, and zero deaths in each. The registry cautions that the named arms are not a like-for-like control comparison. A detailed statistical plan, missing-data approach, analysis populations, and sample-size justification are not reported in the registry record.