Bilateral Dispensing Study of Fanfilcon A Toric Versus Enfilcon A Toric Lenses: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Bilateral Dispensing Study of Fanfilcon A Toric Versus Enfilcon A Toric Lenses (NCT02423109), a randomized na study. The primary outcome is Comfort (Subjective Rating Scale).

2. Clinical Question

In plain terms, the study asked how participants rated comfort while wearing the two toric lens types in the described crossover arrangement. Because the design is a crossover, participants were assigned to one matched pair first and then crossed over to the second matched pair. The registry does not give further detail about the sequence, the timing of the crossover, or how comfort ratings from the two lens periods were compared.

The comfort rating is subjective rather than a direct measurement of a physical property of a lens. It captures participants’ reports on the stated scale, with endpoints described as 0, “cannot be worn. Causes pain,” and 100, “Cannot be felt ever.” The registry identifies ratings at dispensing and after 2 weeks, but it does not report the values for either lens, their variability, or a statistical contrast. Therefore the clinical question can be described from the registered outcome and design, but the posted record does not establish the direction or size of any comfort difference.

3. Trial Design

The registry classifies this as a randomized, double-masked crossover study of fanfilcon A toric and enfilcon A toric lenses. Enrollment was 44, and the trial status is completed. The registry lists the phase as NA. The study description characterizes the intervention as bilateral dispensing over two weeks.

In the arm descriptions, participants are said to be randomized to wear either the test or control as a matched pair and then cross over to the second matched pair. This supports describing the design as a crossover, but the record does not specify the allocation sequence, the order in which the pairs were worn, the length of each treatment period, or whether any washout was used. Those details are not reported in the registry record and should not be inferred.

A crossover design differs from a parallel-group design because a participant can receive both interventions in sequence. General statistical rationale: this can allow a comparison that accounts for characteristics shared by the same participant, but it also makes period, sequence, and carryover considerations relevant. Whether and how the study addressed such considerations cannot be determined from the registry record. The record does not describe a statistical model or identify a specific within-participant contrast.

The primary outcome was comfort on a subjective rating scale at dispensing (baseline) and at the 2-week follow-up. The outcome description says that the analysis population differs slightly because 1 participant was excluded due to a protocol deviation. Numerical outcome summaries and analysis results are not reported in the registry record. The registry lists two outcome measures, but does not provide a numerical result that supports a comparison of the two lens types.

The start is listed as 2015-09 and primary completion as 2016-01. The record identifies CooperVision, Inc. as sponsor. These administrative details identify the registered study, but do not supply the missing outcome estimates or details of the statistical analysis.

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: 44 subjects were enrolled (assigned an ID per protocol), but 11 were not assigned to any group due to screen failure.

Lens 1

Reasons for not completing this period:

Lens 2

Analysis population for the primary outcome, as defined in the registry: Analysis population differs slightly due to 1 participant who was excluded from analysis due to a protocol deviation.

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: Includes the 11 participants who were considered enrolled, but were screen failures and not randomly assigned to a particular arm.

6. Primary Endpoint

The registry lists the primary outcome as Comfort (Subjective Rating Scale), measured over Dispensing (Baseline) and 2 weeks.

The primary endpoint is participant-rated comfort, recorded as a mean on a subjective rating scale. The registry describes ratings at dispensing (baseline) and at the 2-week follow-up. Its scale description gives 0 as “cannot be worn. Causes pain” and 100 as “Cannot be felt ever.” The unit is listed as units on a scale, and the stated measure of dispersion is the standard deviation.

General explanation: a patient- or participant-reported rating can capture an experience that is not fully represented by a clinical measurement or device specification. Comfort is relevant to the experience of wearing a lens, and a numeric scale gives a structured way to record participants’ judgments. The score remains subjective: it reflects how a participant interprets and uses the scale, rather than an objective measurement independent of the participant.

Collecting ratings at dispensing and again at follow-up can describe comfort at more than one point in the study. However, the registry does not say whether the primary comparison was a change from baseline, a follow-up contrast, or another summary of ratings across the crossover periods. The analysis method and numerical means, standard deviations, and contrasts are not reported in the registry record. The stated endpoint therefore identifies what was intended to be measured, but does not by itself show which lens received higher ratings or how precise any difference was.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry describes a continuous primary outcome summarized as a mean with standard deviation. It names a subjective comfort rating as the measure and specifies assessments at dispensing (baseline) and at the 2-week follow-up. It does not report the numerical data or a statistical analysis, so the methods below explain general concepts rather than assert what the investigators used.

What does a mean describe?

General explanation: a mean is a measure of the center of a set of numerical observations. For a comfort scale, it can provide a compact description of the ratings in a group or period. A mean is easier to compare than a list of individual ratings, but it does not show how ratings are distributed, whether they cluster closely, or whether some participants gave notably different ratings. The scale endpoints help interpret the direction of ratings, but a mean alone cannot describe every participant’s experience.

What does the standard deviation add?

General explanation: the standard deviation describes the spread of individual observations around their mean. A smaller standard deviation indicates ratings are more closely grouped around the mean; a larger one indicates more dispersion. It is not the same as the uncertainty in the mean or the uncertainty in a treatment contrast. To evaluate a comparison, the estimate and its uncertainty must be reported with enough information about the design and analysis.

Why does the crossover structure matter?

General explanation: in a crossover study, treatment observations from the same participant are related. A comparison that uses the pairing can account for participant-specific tendencies to give higher or lower comfort ratings. Treating all observations as independent when they are not can misrepresent uncertainty. The registry identifies a crossover and matched pairs, but does not report the statistical model or say whether the analysis used a paired comparison.

Crossover studies can also be affected by period and sequence. A period effect is a change associated with when a treatment is received rather than with the treatment itself. A sequence effect concerns the order in which interventions are received. Carryover refers to an effect of an earlier treatment persisting into a later period. These are general methodological considerations, not findings about this study. The registry does not report whether such effects were assessed, whether a washout was used, or how these issues were handled.

What would a confidence interval communicate?

General explanation: a confidence interval describes uncertainty around an estimated quantity under the assumptions of the statistical method. For a contrast between lens ratings, an interval would show a range of values compatible with the observed data and method. Its width conveys precision: narrower intervals indicate more precise estimates, while wider intervals indicate greater uncertainty. The registry record does not report a confidence interval or a numerical contrast, so precision for the comfort comparison cannot be evaluated.

What does a significance test answer?

General explanation: a significance test assesses how compatible the observed data are with a specified null hypothesis under a statistical model. A p-value is not the probability that the null hypothesis is true, and it does not measure the clinical importance of an effect. A p-value also cannot replace an effect estimate and interval. No p-value or other inferential result for the primary outcome is reported in the registry record.

Why can over-dispersion matter?

General explanation: over-dispersion arises when the variability in data is greater than the statistical model expects. If a model understates variability, its standard errors can be too small and uncertainty can appear lower than it is. This issue is particularly relevant to some count-data models. The stated primary endpoint is a continuous comfort rating, and the registry does not identify a model or report over-dispersion. There is no basis in the registry record to say it was present or that a particular correction was used.

How should planning calculations be understood?

General explanation: a sample-size planning illustration asks how many participants per arm might be needed under specified assumptions to detect a target effect with a chosen significance level and power. Such an illustration is not an observed study result and does not show the probability that this completed trial detected an effect. The registry’s planning description says the illustration uses the observed effect, equal allocation, a two-sided significance level of 0.05, a normal approximation, and target effects stated as fractions of the observed effect. It also distinguishes participants per arm for non-time-to-event outcomes from total events for time-to-event outcomes. No planning sample-size values are stated in the registry record. The illustration is not the trial’s own design justification, and the record does not report the protocol’s sample-size rationale.

Overall, the endpoint description identifies a mean and standard deviation as intended summaries, and the design suggests that dependence between repeated observations may matter. The analysis method, numerical estimates, uncertainty intervals, and tests are not reported in the registry record. General methodological concepts therefore clarify what an analysis could communicate, but cannot fill in the missing study-specific results.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures and indicates that the primary outcome has several categories or time points and was not reduced to one comparison. The comfort endpoint itself is described at dispensing (baseline) and at the 2-week follow-up. The record does not specify which contrast across those assessments was considered primary for inference, or how multiple outcomes, time points, or categories were handled.

General explanation: multiplicity arises when several hypotheses or comparisons are examined. The more comparisons made, the greater the chance that at least one result will appear statistically notable by chance if no adjustment or prespecified hierarchy is used. A statistical plan may address multiplicity through a designated primary contrast, a testing sequence, or another procedure. Whether any such approach was used is not reported in the registry record; no multiplicity adjustment or testing hierarchy should be assumed.

The primary-outcome description says that the analysis population differs slightly because 1 participant was excluded due to a protocol deviation. The registry does not describe the deviation, state which analysis population was used for each outcome, or give a detailed accounting of participants with missing observations. Methods for handling missing data, including whether any imputation was performed, are not reported in the registry record.

These gaps matter because the selected analysis population and treatment of missing observations can affect both the estimate and its uncertainty. In a crossover study, availability of observations from each treatment period can also affect which comparisons are possible. The record does not report enough detail to determine how the exclusion or any incomplete ratings were handled. It also does not report a statistical analysis plan or analysis results. Thus, neither the prespecified inferential approach nor the sensitivity of findings to analysis choices can be assessed from the registry record.

11. 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 lists safety counts separately for Fanfilcon A and Enfilcon A. For Fanfilcon A, the serious-event count is 0 among 33 at risk, the other-event count is 0 among 33 at risk, and the death count is 0. For Enfilcon A, the serious-event count is 0 among 32 at risk, the other-event count is 0 among 32 at risk, and the death count is 0.

These entries mean that the registry reports no events in the listed categories for the stated at-risk groups. They are counts, not estimates of the probability of an event and not a statistical comparison between lenses. A zero count does not prove that the underlying risk is zero; it indicates only that no event in that category is recorded in the stated group in this record. The registry does not provide further descriptions of adverse events, event timing, severity beyond the serious-event category, or a formal safety analysis.

The groups’ at-risk counts should be interpreted as reported, without combining them or treating the figures as evidence of equivalent safety. The safety entries do not replace the primary comfort outcome, and they do not establish a broader conclusion about lens safety beyond the recorded counts.

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

The registry record establishes that a randomized, double-masked crossover study of fanfilcon A toric and enfilcon A toric lenses was completed. It identifies comfort ratings at dispensing and at the 2-week follow-up as the primary outcome. It also records zero serious events, zero other events, and zero deaths in each listed safety group, with the corresponding at-risk counts stated in the safety record.

Those details do not reveal the observed comfort ratings. Numerical means, standard deviations, treatment contrasts, confidence intervals, and test results are not reported in the registry record. As a result, the direction, magnitude, and precision of a comfort difference cannot be determined. The absence of an inferential result does not mean that the two lenses had the same ratings; it means the registry record does not provide the evidence needed to describe a numerical comparison.

Likewise, the zero safety counts should not be interpreted as proof of no risk or as proof that the lenses have equal safety profiles. They describe recorded events in the listed groups, without a reported safety analysis or additional event detail.

General explanation: statistical evidence is most informative when an effect estimate is read together with a measure of uncertainty and an understanding of the design. In a crossover, the relationship between observations from the same participant, the order of treatment, and the analysis population can be important. The registry does not report enough analytic detail to assess those issues or determine how they were incorporated.

The narrow interpretation is therefore descriptive: the record documents the study design, the comfort scale and assessment times, a slight difference in the stated analysis population due to a protocol deviation, and the safety counts. It does not provide sufficient outcome results to establish whether participant-rated comfort differed between the lens types or how precisely such a difference was estimated.

13. Why This Trial Matters Statistically

This study is statistically notable because it uses a crossover design to compare two toric lens interventions and identifies a participant-reported comfort measure as its primary outcome. The design and outcome raise useful questions about repeated observations, within-participant comparisons, and the interpretation of subjective ratings. Those concepts are relevant to many clinical studies that collect measurements from the same participants under more than one condition.

In general, a crossover comparison can take advantage of the fact that each participant experiences both interventions, potentially reducing the influence of stable differences between participants. That advantage depends on appropriate design and analysis. Treatment order, period effects, carryover, and incomplete observations can influence interpretation. The registry identifies randomization, masking, and crossover, but does not supply the details needed to determine how these considerations were handled.

The comfort endpoint also illustrates why a clear measurement description is not equivalent to a reported result. The scale anchors and assessment times clarify what participants were asked to rate. Yet without the numerical ratings and their uncertainty, readers cannot assess the size or precision of any treatment contrast. Reporting a mean and standard deviation would describe central tendency and spread, but a treatment comparison would also need an appropriate estimate and inferential context.

The registry’s statement that one participant was excluded due to a protocol deviation highlights the importance of defining analysis populations and accounting for missing observations. The record does not state how those matters were addressed. Nor does it report a multiplicity strategy despite the outcome record referring to several categories or time points.

For statistical readers, the case demonstrates the limits of interpreting a completed trial record when design features and endpoint definitions are available but numerical analyses are not. It supports discussion of design and reporting principles, but not a conclusion about which lens produced higher comfort ratings.

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 main limitation for interpretation is that numerical primary-outcome results are not reported in the registry record. The record names comfort ratings, their scale, the stated mean and standard deviation summaries, and the assessment times, but does not report the ratings, estimates of a contrast, confidence intervals, or test results. This prevents assessment of the direction, size, and precision of any difference.

The crossover description is brief. It says participants were randomized to wear either the test or control as a matched pair and then crossed over to the second matched pair. The registry does not report the sequence details, period lengths, washout arrangements, or the statistical model. It is therefore not possible to assess how period, sequence, or carryover concerns were handled.

The registry notes that the analysis population differs slightly because 1 participant was excluded due to a protocol deviation, but does not describe the deviation or give further details of the population used for each outcome. Missing-data methods, the number of observed ratings at each assessment, and sensitivity analyses are not reported in the registry record.

The outcome record refers to several categories or time points, but the registry does not specify the inferential comparison or multiplicity procedure. A statistical analysis plan, sample-size justification, and interim-analysis information are not reported in the registry record. The planning description is an illustration based on the observed effect under stated assumptions, not the trial’s own design justification; no planning values are reported.

Safety reporting is also limited to the listed counts and at-risk groups. Further event descriptions and a formal safety comparison are not reported. These limitations restrict conclusions to the registered design, outcome definition, and stated safety counts.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Bilateral Dispensing Study of Fanfilcon A Toric Versus Enfilcon A Toric Lenses — NCT02423109.
• Registry record last updated 2018-01-10; status last verified 2018-01.
• Results first posted 2018-01-10.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry record describes a completed, randomized, double-masked crossover study of bilateral fanfilcon A toric and enfilcon A toric lens dispensing. Enrollment was 44. The registry lists myopia, hyperopia, and astigmatism, and describes a two-week study period. The primary outcome was participant-rated comfort at dispensing (baseline) and at the 2-week follow-up, using a scale from 0, described as “cannot be worn. Causes pain,” to 100, “Cannot be felt ever.”

The record notes that the analysis population differed slightly because 1 participant was excluded due to a protocol deviation. It does not report numerical comfort results or analysis results. Safety entries list zero serious events, zero other events, and zero deaths for each lens group. Further statistical methods, missing-data handling, and multiplicity procedures are not reported in the registry record.