Performance of Toric Hydrogel Lenses Following A Refit With Toric Silicone Hydrogel Lenses for 1 Month: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Performance of Toric Hydrogel Lenses Following A Refit With Toric Silicone Hydrogel Lenses for 1 Month (NCT03835221), a na na study. The primary outcome is Number of Participants With Lens Centration Assessment by the Investigator - Methafilcon A Toric Contact Lenses.

2. Clinical Question

The study aim was to evaluate clinical performance after a refit from methafilcon A to fanfilcon A toric lenses during daily wear. The primary outcome listed in the registry record concerns a baseline centration assessment for methafilcon A lenses. It is not a stated comparison of centration between the two lens types, nor is it a reported post-refit outcome.

The record also lists average daily wearing time and average comfortable wearing time for the lens types as secondary outcomes. However, it does not report their numerical results. The registry record does not report the distribution of centration ratings, so the primary clinical question cannot be answered from the posted outcome information. The design description indicates a sequence of lens wear rather than a randomized comparison; changes across the periods would therefore need to be interpreted with attention to time and order as well as lens type.

3. Trial Design

This was a prospective, single-group study of toric contact lenses. The registry record lists allocation as NA and masking as none. The planned sequence was for all subjects to wear methafilcon A toric contact lenses for four (4) weeks of daily wear, followed by refitting with fanfilcon A toric contact lenses for four (4) weeks of daily wear. Enrollment was 43.

Because the same planned sequence applies to all subjects, the earlier methafilcon A period is not a randomized or concurrent control arm. Comparing outcomes across the two periods would not isolate lens type from changes related to the order or timing of observation. The registry record does not describe random assignment, masking, or a separate control group. It also does not report whether every enrolled participant completed both periods.

The study is listed as completed. Its primary outcome is an investigator assessment of lens centration for methafilcon A toric contact lenses at baseline. The record lists 41 outcome measures, including secondary outcomes for average daily wearing time and average comfortable wearing time. It lists zero analyses. The registry record does not report a protocol-level statistical analysis plan, sample-size justification, interim analyses, or analysis populations. Those details should not be inferred from the design description or the listed outcome measures.

The sequential design can support descriptive observations about each wear period if results are reported, but the posted record does not provide those outcome estimates. In particular, the design description alone cannot establish how centration, wearing time, or comfort differed across the periods. The absence of masking may also matter for outcomes that involve investigator assessment or participant experience, but the registry record does not describe procedures intended to address this issue.

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.

Methafilcon A

Reasons for not completing this period:

Fanfilcon A

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 Number of Participants With Lens Centration Assessment by the Investigator - Methafilcon A Toric Contact Lenses, measured over Baseline.

The primary outcome is titled as the number of participants with a lens centration assessment by the investigator for methafilcon A toric contact lenses. The assessment was scheduled at baseline. Its description specifies a three-point scale: 1=optimal centration, 2=decentration acceptable, and 3=decentration unacceptable.

Centration describes how the lens sits relative to the intended position on the eye. An investigator assessment can record whether the lens appears well centered or decentered, and the ordered scale distinguishes acceptable from unacceptable decentration. Such assessments can be useful in evaluating lens fit, while remaining distinct from participant-reported comfort or wearing time.

The outcome title describes a count of participants with an assessment, while the scale description explains the rating used during that assessment. The registry record does not report the number of participants in each rating category, or the number with an assessment. It therefore does not show the observed distribution of centration ratings. The baseline timing also matters: this endpoint, as listed, does not itself measure a change after refitting to fanfilcon A lenses.

In general, an endpoint should be interpreted according to its definition, scale, and timing. A count of assessments is not the same as a count of participants with optimal centration, and a rating scale is not interchangeable with a continuous measurement. The registry record does not give further details about how ratings were summarized or analyzed.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record describes a prospective, single-group sequence, but it does not report the statistical methods used to analyze the outcomes. The explanations below are general statistical context, not a description of unreported methods from this study.

What does the endpoint measure?

The primary outcome is a count of participants with an investigator lens-centration assessment for methafilcon A toric contact lenses at baseline. The assessment itself uses an ordered three-point scale: 1=optimal centration, 2=decentration acceptable, and 3=decentration unacceptable. A count of participants assessed and the distribution of their ratings answer different questions. The first describes assessment availability; the second describes the ratings among assessed participants. The registry record does not provide either set of results.

In general, the scale is ordinal: its categories have a stated order, but the distances between adjacent categories are not established as equal. Analyses of ordinal ratings should respect that structure. Treating the ratings as continuous measurements would require additional assumptions about the scale that are not documented in the registry record.

What does a confidence interval mean?

In general, a confidence interval expresses uncertainty around an estimated quantity under the assumptions of the analysis. A narrower interval indicates greater precision for that estimate, while a wider interval indicates less precision. The interval does not show the probability that a fixed true value lies inside it. Interpretation depends on how the data were collected, which participants were analyzed, and which statistical model was used. No confidence interval for the primary outcome is reported in the registry record.

Why does the sequence matter?

For a comparison across repeated periods, it can be useful to account for the fact that measurements from the same participant are related. Such paired or repeated observations are not generally independent. More broadly, a fixed sequence can combine differences associated with the lens with differences associated with time or order. Randomized ordering or a concurrent comparison may help address some sources of bias, but the registry record does not describe either. No particular adjustment method can be attributed to this study.

How should event counts be interpreted?

The record’s safety entries are counts of participants with events among those listed as at risk. Counts provide information about how many participants were recorded with an event; they do not, by themselves, describe event severity beyond the category in which they are reported, the timing of events, or the completeness of reporting. A zero count means no event was recorded in that listed group, not that the possibility of an event has been ruled out.

In general, estimates based on counts can be imprecise when event numbers are small. Confidence intervals can communicate uncertainty, but none is reported for the safety counts in the registry record. The record also does not give event-level descriptions or follow-up details that would support a more detailed safety analysis.

What is over-dispersion?

In general, over-dispersion occurs when observed variation in count data is greater than a model assumes. If a count model assumes more regular variation than the data contain, standard errors may be too small and confidence intervals may be too narrow. Analysts may use a model that allows additional variation when the data and design support it. This is general statistical context; the registry record does not report a count model or an assessment of over-dispersion.

What do the planning assumptions mean?

The sample-size assumptions describe a planning illustration based on an observed effect, not the trial’s own design. The listed assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation; the effect to detect is a stated fraction of the observed effect. For time-to-event illustrations, the assumption refers to the total number of events; other illustrations refer to participants per arm. These hypothetical assumptions do not make the actual sequential study a two-arm randomized trial and are not observed power. The registry record does not report its own sample-size justification, and it does not report a primary effect estimate in the posted results.

Overall, the statistical method needed to analyze a result depends on the outcome scale, timing, participant structure, missing data, and study design. Because the record does not report an analysis plan or results for the primary outcome, a particular model, test, adjustment, or inferential conclusion should not be inferred.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 41 outcome measures, including secondary outcomes for daily wearing time and comfortable wearing time, and it lists zero analyses. It does not report how many outcomes were designated as primary in the full protocol, whether comparisons were prioritized, or whether any adjustment for multiple testing was planned. When many outcomes are examined, the chance of at least one apparently unusual result can increase; multiplicity procedures or a clear hierarchy of outcomes can help address that issue. This is general statistical context, not a description of a method used in this study.

The record does not report a missing-data plan, the number of participants with missing outcome values, or reasons for missingness. It also does not state which participants were included in each outcome analysis. Those details are important because an estimate based only on participants with observed measurements can differ from an estimate that accounts for missing observations, especially if missingness is related to participant experience or outcome values.

The safety listings give at-risk denominators of 43 for methafilcon A and 42 for fanfilcon A, but the registry record does not describe participant flow between periods or explain the denominators. The enrollment figure alone does not establish the analysis population for each endpoint. The registry record also does not report whether analyses followed an intention-to-treat, per-protocol, or other population definition. These omissions limit assessment of completeness, selective reporting, and how closely any analysis would represent the planned study population.

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 record lists zero serious adverse events among 43 participants at risk in the methafilcon A toric contact lens group, and zero among 42 participants at risk in the fanfilcon A toric contact lens group. It also lists zero other adverse events in each group and zero deaths in each group. These are the posted counts and denominators.

The denominators differ between the two lens periods. The registry record does not explain why, and the safety figures should not be treated as evidence that the same number of participants contributed information in both periods. The record also does not report event timing, participant-level details, follow-up completeness, or confidence intervals for these counts.

In general, a zero recorded count means that no event of that category was recorded among the listed participants at risk. It does not establish that the risk is zero or rule out events that were not captured or reported. The counts describe the registry’s safety entries; they do not by themselves support a comparative safety conclusion between the lenses.

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

The registry record establishes that this was a prospective study of habitual methafilcon A toric lens wearers planned to wear those lenses before being refitted with fanfilcon A toric lenses. It identifies an investigator-assessed baseline centration outcome and lists wearing-time outcomes. It also reports safety counts and the numbers at risk in each lens group. These details describe the study and its recorded outcomes, but they do not provide a numerical result for the primary endpoint.

What the record does not show is the distribution of centration ratings, the number of participants with an assessment, or numerical results for daily and comfortable wearing time. It does not report effect estimates, confidence intervals, p-values, or a statistical analysis plan. Without those results, the posted record cannot establish the magnitude or precision of a difference in performance across the lens periods.

The study’s fixed sequence also limits interpretation of any comparison across periods. Because methafilcon A wear precedes fanfilcon A wear for all subjects in the planned design, lens type and period are not separated by randomized assignment. General changes over time, order effects, or other period-specific influences could contribute to differences. This does not negate the value of descriptive observations, but it means that the sequence is not equivalent to a randomized, concurrent comparison.

The zero recorded adverse-event counts are limited observations within the listed at-risk groups. They do not prove that no risk exists, and the record does not provide details needed to assess event capture or follow-up. Overall, the available record supports a description of the intended study and its listed safety counts, but not a conclusion about comparative efficacy, comfort, wearing time, or safety.

13. Why This Trial Matters Statistically

This study illustrates why the design and the endpoint definition need to be considered together. The intended sequence is a refit from one lens type to another, with the same planned order for all subjects. That structure differs from a randomized comparison with concurrent groups. If measurements across the periods are compared, the interpretation must account for the possibility that period and order accompany the change in lens type.

The primary outcome also demonstrates the importance of distinguishing what an endpoint is called from what its results would show. The listed endpoint is the number of participants with an investigator centration assessment at baseline, while the description specifies an ordered rating scale. Neither the count of assessed participants nor the distribution of ratings is reported. Without those results, the endpoint’s clinical interpretation remains open.

The record further illustrates the difference between outcomes named in a registry and analyses reported from those outcomes. It lists 41 outcome measures but zero analyses, and does not give statistical methods or estimates for the primary endpoint. Listing outcomes alone does not reveal whether the analyses were prespecified, how missing observations were handled, or how multiple outcomes were considered.

Finally, the safety counts show why denominators and event categories must accompany event counts. The record gives at-risk counts for each lens period and reports zero serious events, other events, and deaths, but does not explain the difference in denominators or provide event-level context. These limitations make careful, restrained interpretation essential: the study record can be informative about planned design and reporting, even when it does not provide the result needed to answer the main comparative question.

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 leaves several trial-specific uncertainties. It lists enrollment as 43, but does not report the number completing each lens period or the number contributing data to each outcome. The adverse-event listings give different at-risk denominators for the two lens groups, and the record does not explain that difference. It also does not describe withdrawals, protocol deviations, or reasons for missing outcome data.

The primary outcome is a baseline assessment for methafilcon A lenses, while the study aim describes evaluating performance after refitting to fanfilcon A lenses. The record does not report a corresponding centration result after refitting or the distribution of baseline ratings. This limits the extent to which the listed primary measure can address the stated refit question.

The single-group, fixed-order design does not provide a randomized concurrent comparison. As a result, any differences across periods could be associated with time or sequence as well as lens type. Masking is listed as none, and the record does not describe other procedures intended to reduce assessment or expectation effects.

The record does not report the statistical analysis plan, sample-size justification, multiplicity approach, analysis populations, or methods for handling missing data. Although it lists secondary outcomes and 41 outcome measures, it gives no numerical results for the primary or secondary outcomes and lists zero analyses. These reporting gaps prevent assessment of the precision, completeness, and statistical interpretation of the clinical outcomes.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Performance of Toric Hydrogel Lenses Following A Refit With Toric Silicone Hydrogel Lenses for 1 Month — NCT03835221.
• Registry record last updated 2020-06-11; status last verified 2020-05.
• Results first posted 2020-06-11.
• 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

NCT03835221 is a completed prospective study of toric contact lenses in participants described as habitual methafilcon A toric lens wearers. The planned sequence was four (4) weeks of daily methafilcon A wear followed by refitting with fanfilcon A lenses for four (4) weeks of daily wear. Enrollment was 43; allocation is listed as NA and masking as none.

The primary outcome is the number of participants with an investigator lens-centration assessment for methafilcon A lenses at baseline. The rating scale has three categories, from optimal centration to unacceptable decentration. The record lists 41 outcome measures and zero analyses, but does not report numerical primary or secondary outcome results or statistical methods.

For safety, the registry lists zero serious adverse events, zero other adverse events, and zero deaths in both lens groups, with 43 participants at risk for methafilcon A and 42 for fanfilcon A. The record does not explain the denominator difference or provide further event details.