Comparison of Two Toric Contact Lenses on Current Toric Wearers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Two Toric Contact Lenses on Current Toric Wearers (NCT00639379), a randomized na study. The primary outcome is Lens Orientation Within 5 Degrees.

2. Clinical Question

In practical statistical terms, the study asks whether the recorded early orientation outcome differs between the two toric lenses when each is used in a crossover setting. The crossover structure means participants were assigned to a sequence rather than simply remaining in one treatment group throughout the study. Both eyes were included in the outcome description, so eye-level results may involve more than one observation per participant.

The registry’s brief summary says the investigation considered comfort, vision, toric fit characteristics, and corneal integrity. The primary outcome posted in the results, however, is specifically lens orientation within 5 degrees at one minute after insertion. The record lists five outcome measures and five analyses, but does not provide secondary posted outcomes. Therefore, the clinical question that can be assessed from the posted primary result is narrower than the set of aims described in the brief summary.

3. Trial Design

This was a randomized, single-masked, crossover investigation of two toric contact lenses. The official title describes a multicenter, subject-masked, two-week crossover design, while the brief summary describes a four-week study with two-week wear periods. The intervention descriptions specify daily-wear lenses, and the study was bilateral. The registry marks the study as completed.

The two lenses were senofilcon A toric and alphafilcon A toric. Participants were assigned to one of two sequences: senofilcon A followed by alphafilcon A, or alphafilcon A followed by senofilcon A. The adverse-event record lists 44 participants at risk in the first sequence and 45 in the second. Those sequence-specific figures are reported as given and are not the same as the primary outcome population description, which states that 84 subjects and 168 eyes completed the study and were analyzed.

Overall enrollment is listed as 89. The record does not explain the relationship between enrollment, the sequence-specific safety populations, and the completed-study analysis population. It also does not report reasons for non-completion or describe whether any participants contributed incomplete outcome data.

Masking is listed as single, and the study title clarifies that subjects were masked. The registry does not state whether investigators, clinical assessors, or analysts were masked. The record lists the study start as 2008-02 and primary completion as 2008-06. It identifies Johnson & Johnson Vision Care, Inc. as the sponsor.

In a crossover study, each participant can receive both interventions in sequence. This can support within-participant comparisons, but the analysis needs to account for the paired structure and may need to consider period or sequence effects. These are general design considerations; the registry record does not specify how such effects were handled. It reports logistic regression as the method for the primary comparison, without a fuller model description.

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.

Period 1 - 2 Weeks

Reasons for not completing this period:

Period 2 - 2 Weeks

Analysis population for the primary outcome, as defined in the registry: Subjects/eyes that completed the study were analyzed. A total of 168 eyes/84 subjects were analyzed.

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 Lens Orientation Within 5 Degrees, measured over 1 minute after insertion.

The primary endpoint is the number of eyes with lens orientation within 5 degrees of optimal orientation within one minute of contact lens insertion. It is recorded as a count, with eyes as the unit. The outcome captures how closely the lens aligns soon after insertion, using a specified angular threshold and assessment time.

This kind of endpoint is useful for describing an aspect of toric lens fit. Toric lenses are designed to correct astigmatism, and orientation is relevant to whether the lens sits at an intended position. The endpoint is a focused measure of early orientation; it is not a direct measure of comfort, visual acuity, longer-term stability, or corneal integrity. Those broader domains appear in the study summary, but are not the primary endpoint reported in this record.

The population description says 168 eyes from 84 subjects were analyzed. The two arm entries each report a value of 128, while their listed group sizes are 84. Because the endpoint is a count of eyes, and the record does not explain the relationship between these entries, their meaning cannot be reconciled from the registry record alone. The values should therefore be read as posted, not treated as a directly interpretable proportion or as a basis for inferring the number of eyes meeting the threshold.

The timeframe is one minute after insertion. It does not describe repeated measurements or later performance. The record does not state who assessed orientation, how optimal orientation was defined operationally, or whether assessment procedures were standardized across centers.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a count of eyes meeting a binary condition: lens orientation is within 5 degrees of optimal orientation one minute after insertion, or it is not. The registry labels the outcome as a count and reports logistic regression for the comparison. In general, logistic regression models the probability of a binary outcome, often by modeling the log odds. The odds ratio expresses a comparison of odds between groups, but its direction depends on how the event and reference group are coded.

The registry reports an odds ratio of 0.967 and an interval from 0.436 to 0.967 at a 98.98% confidence level. A confidence interval describes uncertainty around an estimated quantity under the assumptions of the statistical model. In repeated use of the same procedure, intervals constructed at a stated confidence level are intended to contain the target quantity at that rate, assuming the model and sampling conditions are appropriate. A confidence interval is not a probability statement that the particular fixed effect lies inside the observed interval.

Here, interpretation is limited by missing model details. The record does not state which lens is the reference, how the event was coded, or whether the analysis accounts for crossover pairing, study period, treatment sequence, center, or the two eyes within a participant. The point estimate coincides with the reported upper endpoint, and the interval is reported at 98.98%; these details should be read as recorded rather than silently converted to a conventional interval or treated as evidence of a particular direction. The record does not provide a p-value.

The analysis is classified in the registry as non-inferiority or equivalence. These are related but distinct inferential aims. In general, a non-inferiority analysis asks whether the data rule out a loss larger than a prespecified margin in a chosen direction. An equivalence analysis asks whether the uncertainty is sufficiently contained within prespecified bounds on both sides. Neither conclusion follows merely from an odds ratio close to one, a lack of a reported p-value, or equal values in the arm entries. The margin, direction, hypotheses, and analysis decision rule are not reported in the registry record.

A crossover design has a paired structure: the same participant receives both interventions in different periods. In general, this can reduce variation from stable differences between people, because each participant can contribute information under both treatments. It also makes the analysis dependent on the sequence and timing of treatment. Period effects, sequence effects, or carryover from an earlier period can complicate interpretation. The record describes two-week periods but does not say whether carryover was assessed, whether a washout was used, or how period and sequence were handled statistically.

The primary outcome description includes eyes from the same participants. In general, outcomes from two eyes of one person may be correlated rather than independent. Treating correlated eye measurements as independent can affect standard errors and confidence intervals. The record does not explain whether the analysis handled this within-person clustering. It also does not report the number of eyes contributing to each arm beyond the arm entries, or explain how the count values relate to the stated analysis population.

The record’s five outcome measures and five analyses indicate that multiple outcomes or analyses were registered, but no secondary results are posted. In general, when many hypotheses are tested, the chance of at least one apparently notable result can increase unless the analysis plan addresses multiplicity. The registry record does not report an adjustment strategy, a hierarchy of outcomes, or which comparisons were confirmatory. It is therefore not possible to determine how multiplicity was handled.

For a count endpoint, the reported count needs a clearly defined denominator and a consistent unit of analysis before a rate or comparative probability can be interpreted. The record gives arm values of 128 and arm sizes of 84, while describing 168 analyzed eyes. It does not explain the count entries, so no rate should be inferred from them. The primary result is also not accompanied by a posted p-value or full model specification.

General principles of interval interpretation do not resolve these reporting gaps. A precise interval would typically require a clearly defined estimand, analysis population, coding scheme, and variance calculation. In this record, those details are unavailable. The numerical interval and model label can be reported faithfully, but they do not independently establish a clinically meaningful difference, non-inferiority, or equivalence.

The registry includes a sample-size-planning illustration based on the observed effect, using a two-sided significance level of 0.05, equal allocation, and a normal approximation. Such calculations are planning illustrations rather than observed power. The numerical planning results are not stated in the registry record considered for this interpretation, and they cannot substitute for a reported design justification. The record does not report the trial’s own sample-size justification or any interim analysis plan.

10. Analyses Reported by the Sponsor

The posted analysis is a logistic-regression comparison with an odds ratio of 0.967 and a reported interval from 0.436 to 0.967 at a confidence level of 98.98%. The analysis is classified as non-inferiority or equivalence. No p-value, margin, event coding, reference group, or complete model specification is reported.

No recalculated comparison is reported for this count endpoint. The registry notes that values are missing or not estimable for a two-arm comparison of this endpoint type. Accordingly, there is no unadjusted re-calculation to set alongside the reported regression result. The arm entries are both 128, but the count and population details are not reconciled in the record, so deriving a separate comparative estimate from them would not be justified.

The sponsor’s own analysis takes precedence if a discrepancy is flagged. The registry does not flag a discrepancy for this result. That does not resolve the limitations in interpretation: the interval’s upper endpoint equals the point estimate, and the non-inferiority or equivalence margin and coding details are absent. The reported estimate should therefore be distinguished from a fully assessable claim of non-inferiority or equivalence.

11. Multiplicity, Missing Data and Analysis Populations

The registry lists five outcome measures and five analyses, but reports no secondary posted results. It does not identify a multiplicity adjustment, a hierarchy among outcomes, or which analyses were prespecified as primary for inferential testing. In general, multiple testing can increase the chance of a nominally notable result when many comparisons are examined. Without the analysis plan, it is not possible to determine whether or how that issue was addressed.

The primary analysis is described as logistic regression, but the registry does not report the model formula or covariates. It does not state whether the crossover periods and sequences were included, whether the participant-level pairing was represented, or how the two eyes from each participant were handled. These details affect interpretation of model-based uncertainty.

The outcome population is described as subjects and eyes that completed the study, with 84 subjects and 168 eyes analyzed. Overall enrollment is listed as 89. The registry does not explain the relationship between those figures, provide reasons for non-completion, or describe missing outcome observations. The analysis population is therefore identifiable as completers, but the treatment of missing data and the consequences of any missingness are not reported.

The record does not say whether the analysis used an intention-to-treat, per-protocol, or other population for the non-inferiority or equivalence assessment. This is relevant because general non-inferiority methods can be sensitive to the analysis population and deviations from assigned treatment. No protocol deviations, adherence information, or sensitivity analyses are reported in the registry record.

The registry does not report an interim analysis plan or a detailed statistical analysis plan. It also does not explain the endpoint count entries, which are 128 for each lens, in relation to the analyzed eyes. These omissions limit assessment of both the analysis population and the robustness of the primary comparison.

12. 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 adverse-event record lists two treatment sequences. For the sequence senofilcon A toric followed by alphafilcon A toric, 44 were at risk for serious events and 44 for other events; zero affected participants are reported in each category. For the reverse sequence, 45 were at risk for serious events and 45 for other events; zero affected participants are reported in each category.

These are registry-recorded event figures for the specified risk groups. They do not establish that no events occurred outside the recorded categories, and they do not describe event severity beyond the serious and other groupings. The record lists no serious adverse-event terms among the leading terms.

Deaths are recorded as not reported in the registry record. A missing death count should not be interpreted as a reported zero. The safety figures are organized by treatment sequence, rather than presented as a complete lens-specific comparison, and the record does not describe the method or period used to collect adverse events. They are therefore a limited account of the safety information posted in the registry.

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

The result can be described as a randomized, subject-masked crossover comparison of two toric lenses, with a primary endpoint concerning early lens orientation. The registry reports equal count values of 128 in the two arm entries and a logistic-regression odds ratio of 0.967. The reported interval is 0.436 to 0.967 at a confidence level of 98.98%. These are the posted numerical results, but their statistical meaning is constrained by missing endpoint and model details.

The result does not, by itself, establish that the lenses are equivalent or that one is non-inferior to the other. The registry’s classification of the analysis as non-inferiority or equivalence does not replace the missing margin, direction, and decision rule. The estimate’s direction also cannot be interpreted without knowing how the event and reference group were coded.

The arm values do not establish the percentage of eyes meeting the orientation threshold. The primary endpoint is described as a count of eyes, yet the arm values, arm sizes, and analyzed-eye description are not reconciled. No denominator should be inferred from these entries. Likewise, the reported model estimate cannot be independently checked from the posted count information.

The one-minute orientation measure does not establish performance on the other domains mentioned in the brief summary, such as comfort, vision, or corneal integrity. No secondary outcome results are posted. The safety entries report zero affected participants in the stated serious and other event categories for both sequences, while deaths are not reported in the registry record. These figures should be understood as the available registry entries, not as a comprehensive statement about all possible harms.

Overall, the record gives a limited numerical account of the primary outcome and an analysis label, but not enough detail to make a complete inferential judgment. It is appropriate to report the observed entries and the reported model result while keeping the outcome-count ambiguity and missing analytic details explicit.

14. Why This Trial Matters Statistically

This trial illustrates why the statistical unit and denominator matter. The primary endpoint is described as a count of eyes, and the population description gives 168 analyzed eyes from 84 subjects. Yet each lens arm reports a count value of 128 alongside an arm size of 84. The registry does not explain how those pieces fit together. Without that clarification, readers cannot safely turn the posted counts into rates or use them to independently reproduce the comparison.

The crossover design also makes the analysis structure important. Participants received the lenses in different sequences, and each participant may contribute data under both treatments. Eye-level outcomes add another level of possible dependence. A model must reflect the design to produce uncertainty estimates that match the data structure. The registry names logistic regression but does not explain how pairing, periods, sequences, or eyes were handled.

The non-inferiority or equivalence label highlights a further principle: a point estimate near one is not enough to establish equivalence. Such conclusions require prespecified margins and a decision rule. The registry does not report the margin, while the reported interval has the point estimate at its upper endpoint. This makes transparent reporting especially important.

Finally, the record demonstrates the distinction between a trial’s broad stated aims and the endpoint with posted results. Comfort, vision, toric fit, and corneal integrity are mentioned in the summary, but only the primary orientation result is described in the posted analysis. A statistical interpretation should stay tied to the outcome actually reported and avoid extending it to outcomes for which results are unavailable.

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 primary count entries are difficult to interpret alongside the stated population. The endpoint is a number of eyes, the analyzed population is 168 eyes from 84 subjects, and each arm reports 128 with an arm size of 84. The registry does not explain those figures or define a denominator for the values. This limits direct interpretation of the arm results.

The statistical report is incomplete for assessing the odds ratio. Event coding, reference group, model terms, handling of crossover pairing, period and sequence effects, and correlation between eyes are not described. The reported interval runs from 0.436 to 0.967, with the point estimate at its upper endpoint, and is stated at a 98.98% confidence level. No p-value is reported.

The registry classifies the analysis as non-inferiority or equivalence but does not report the margin or the decision rule. It also does not identify the analysis population for that assessment. The outcome population is described as completers, but reasons for non-completion and missing-data handling are not reported.

Although five outcome measures and five analyses are listed, no secondary results are posted, and multiplicity handling is not described. The brief summary names clinical domains beyond orientation, but their results are unavailable in the registry record. The record also does not state whether assessors beyond subjects were masked, whether there was a washout, or how the orientation assessment was standardized across centers.

These limitations do not change the posted numerical entries, but they restrict what can be inferred from them. In particular, the registry record does not support reconstructing a complete independent analysis or a formal non-inferiority or equivalence conclusion.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Comparison of Two Toric Contact Lenses on Current Toric Wearers — NCT00639379.
• Registry record last updated 2015-05-21; status last verified 2015-05.
• Results first posted 2010-07-19.
• 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

This completed randomized, single-masked, bilateral crossover study compared senofilcon A toric with alphafilcon A toric daily-wear contact lenses in current toric wearers. The registry lists enrollment of 89 and describes 84 subjects and 168 eyes as completing the study and contributing to the primary outcome analysis.

The primary endpoint counted eyes with lens orientation within 5 degrees of optimal orientation one minute after insertion. Both arm entries report a value of 128. The registry also reports a logistic-regression odds ratio of 0.967, with an interval from 0.436 to 0.967 at a confidence level of 98.98%, classified as a non-inferiority or equivalence analysis.

The record does not report a p-value, an inferential margin, event coding, detailed model specification, or secondary outcome results. It does not explain how the arm counts relate to the analysis population. Safety entries report zero serious and other events in the listed sequence groups; deaths are not reported in the registry record.