On-Eye Evaluation of Contact Lens Axis Location: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for On-Eye Evaluation of Contact Lens Axis Location (NCT02100410), a randomized na study. The primary outcome is Percentage of Lenses With Axis Orientation ≤ 10 Degrees From Ideal Location After 3 Minutes of Wear.

2. Clinical Question

The clinical question is therefore about the observed rotational positioning of marked toric lenses shortly after placement, rather than about a patient-level clinical outcome. The axis mark was reviewed at the slit lamp and its observed location was compared with an iteration-specific ideal position. The study also posted secondary measures of lens awareness and handling on removal, but those measures address different aspects of lens experience and do not replace the primary axis-orientation question.

3. Trial Design

This was a randomized, single-masked, crossover study. The registry lists enrollment of 50 and a completed status. The start and primary completion are both recorded as 2013-04. The phase is listed as NA. Alcon Research is identified as sponsor. The study was described as a 1-visit evaluation, with each participant wearing three pairs of study lenses, one pair for each design iteration.

Within each pair, the lenses were worn contralaterally: the embossed-mark lens was worn on the right eye and the lens without an embossed mark was worn on the left eye. The pairs corresponded to iterations 2-87-1, 2-87-2, and 2-87-3, and each pair was worn for approximately 30 minutes. The brief summary says the purpose was to evaluate axis location after 3 minutes of wear. This means the primary assessment concerned an early point within each wear period, not the entire exposure period.

Randomization and masking are recorded, but the order of the iterations, the method of randomization, and the person or persons masked are not reported in the registry record. The record also does not explain how the crossover sequence was incorporated into the primary analysis. In a crossover design, each participant experiences more than one study condition, so outcomes can be related within a participant. That structure can be important for analysis; the posted primary results, however, are group percentages without a reported model or paired comparison.

The primary analysis population is described as randomized participants satisfying all inclusion and exclusion criteria. The posted primary outcome lists 49 lenses for each of TEST1, TEST3, and TEST5. The record does not explain why those outcome counts differ from the enrollment figure or whether any randomized participants or measurements were excluded. The secondary outcomes are reported for Day 1. No protocol-level explanation of allocation sequence, analysis population handling, or crossover modeling is reported in the registry record.

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: Of the 50 enrolled, 1 participant was exited as a screen failure prior to randomization and exposure to the study product. This reporting group includes all randomized participants (49).

Exposure Pair 1, 30 Minutes

Exposure Pair 2, 30 Minutes

Exposure Pair 3, 30 Minutes

Analysis population for the primary outcome, as defined in the registry: This analysis population includes all all randomized participants satisfying all of the inclusion/exclusion criteria.

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: This analysis population includes all subjects/eyes exposed to the investigational products (embossed or non-embossed lenses).

6. Primary Endpoint

The registry lists the primary outcome as Percentage of Lenses With Axis Orientation ≤ 10 Degrees From Ideal Location After 3 Minutes of Wear, measured over Day 1.

The primary endpoint is the percentage of lenses with axis orientation no more than 10 degrees from the ideal location after 3 minutes of wear. Axis orientation describes the rotational position of a toric lens on the eye. The axis mark was evaluated during slit-lamp review, and its observed location was compared with the ideal location for that lens iteration. The ideal position differed by iteration: it was either 6 o'clock or 3 and 9 o'clock.

This endpoint turns a measured angular deviation into a threshold-based summary. It counts a lens as meeting the endpoint when the observed axis mark is within the specified 10-degree band around its ideal position. Such a measure is used to describe how frequently lenses meet a prespecified positioning criterion at the stated assessment time. It is not the same as reporting the average rotational deviation: lenses just inside and just outside the threshold fall into different categories, while the exact deviation within either category is not represented by the percentage.

The endpoint was prespecified for embossed lenses only: TEST1, TEST3, and TEST5. The record gives percentages for those groups but no confidence intervals, event counts, or inferential test for comparing iterations. The percentages therefore describe the posted results but do not convey their precision or establish the statistical significance of differences among lens designs.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is a binary classification at the lens level: whether axis orientation was within the specified 10-degree limit of the iteration-specific ideal location after 3 minutes of wear. A percentage is a descriptive way to express how often the criterion was met in a group. It is useful because it gives the reader a direct sense of the frequency of lenses meeting the target. It does not retain all the information in the underlying angular measurements, and it does not indicate how uncertain the percentage is unless an uncertainty measure is also reported.

The registry reports the primary outcome as a number, with the unit described as a percentage of lenses. It does not post the numerator counts, confidence intervals, or a comparison model. The number 49 is listed for each embossed lens group, but the results do not provide the event counts behind the percentages. These omissions matter because percentages alone cannot show the precision of an estimate as clearly as a confidence interval can. A confidence interval is a range of values compatible with the observed data under a specified statistical model and its assumptions. It conveys uncertainty, not a guarantee that the true value lies within the interval.

No primary p-value or inferential comparison is reported. A p-value, in general, summarizes how unusual observed data would be under a specified null hypothesis and statistical model. It is not a measure of the size or importance of an effect, and it cannot establish that an observed pattern will recur. Because there is no primary inferential analysis in the registry record, no p-value should be inferred from the displayed percentages. The percentages can be described directly without presenting an unsupported test.

The study has a crossover structure: participants wore multiple study pairs, and the lenses within a pair were worn in opposite eyes. In general, crossover data can contain within-participant dependence: measurements from the same participant may be more alike than measurements from different participants. A method that treats every lens observation as independent can misstate uncertainty when that dependence is present. Conversely, a paired or repeated-measures analysis can use the within-participant structure if the relevant data and design details are available. The registry does not report the primary statistical method, sequence allocation, or any modeling of participant-level dependence, so it is not possible to assess whether the posted primary summaries reflect that structure.

The three design iterations also differ in their ideal axis location, with the ideal specified as either 6 o'clock or 3 and 9 o'clock. That iteration-specific definition is part of the outcome, not a common raw angular target across all designs. The binary threshold makes the outcome interpretable against each iteration's stated ideal, but it also means that the exact angular errors are not visible in the posted primary percentages. The record describes measurement by slit-lamp review and comparison with the ideal position, but does not report assessor reliability, repeatability, or a measurement-error analysis.

The secondary outcomes are continuous summaries in units on a scale. The registry provides means and standard deviations for Lens Awareness and Handling on Removal. A mean describes the arithmetic center of a set of values; a standard deviation describes the spread of individual values around that mean. These summaries do not show the full distribution, and the record does not name the scale range or explain its scoring direction. Interpretation should therefore remain tied to the labels and units posted in the registry rather than assume what a particular score means clinically.

The mean-difference comparisons for selected secondary groups are simple unadjusted re-calculations from the posted summary statistics. Their confidence intervals describe uncertainty in the estimated mean difference under the calculation's assumptions. An interval that includes zero is compatible with no mean difference under that method; an interval that does not include zero indicates a contrast away from zero under the same assumptions. These comparisons are not identified as sponsor-reported analyses: the registry lists no reported analyses for these endpoints. Their p-values are unadjusted, so they do not account for the number of secondary outcomes or pairwise comparisons considered.

The planning illustrations are not observed power and do not describe the original trial's design justification. They use the observed effect and assume a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The listed group sizes are participants per arm for 80% or 90% power at specified fractions of the observed effect. As general statistical guidance, planning calculations based on an observed effect can be unstable: a small study's estimated effect may be imprecise, and planning for a smaller fraction of that effect requires more participants than planning for the full observed effect. These illustrations should not be treated as evidence that the study was adequately powered or as a substitute for a protocol-based design calculation. The registry does not report the original sample-size justification.

For a count outcome, over-dispersion is a general concern when observed variability exceeds what a simple count model assumes. In that situation, a basic model can produce standard errors that are too small and confidence intervals that are too narrow. The primary outcome is posted as a percentage of lenses rather than as a count model, and no dispersion estimate or model is reported. This concept therefore explains a general analytical issue, not a finding in this trial. More broadly, the registry record does not report the primary estimation method, an adjustment strategy, or a statistical analysis plan, so model-specific assumptions cannot be checked against the posted results.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two secondary outcomes and no reported analyses. It does not report a multiplicity strategy, such as a prespecified hierarchy of outcomes or an adjustment to account for testing multiple comparisons. The unadjusted secondary p-values therefore have a limited role: they summarize individual comparisons without controlling the overall chance of false-positive findings across the set of analyses. They should not be read as if they came from a single confirmatory test.

For the primary endpoint, the registry posts descriptive percentages but no inferential comparison, p-value, or confidence interval. The absence of those measures means that the precision of the primary percentages and the uncertainty in differences among iterations are not quantified in the posted record. It is not possible to determine from the registry whether an analysis was conducted but not posted, or whether no inferential analysis was planned; the analysis plan is not reported in the registry record.

The stated primary analysis population includes randomized participants satisfying all inclusion and exclusion criteria, but the registry does not describe the handling of missing measurements, exclusions after randomization, or any imputation method. The reported primary outcome counts are 49 for each embossed lens group, while enrollment is 50. The record does not explain this difference, so no reason for it should be inferred. It also does not report whether the same participants contributed to every endpoint or whether missingness varied by outcome.

These gaps matter because exclusion and missing-data decisions can affect both the population represented by a result and the uncertainty around it. In a crossover study, it is also relevant whether participants completed all lens periods and how incomplete sequences were handled. Such details are not reported in the registry record. The posted results therefore support description of the available summaries, but not an assessment of the effects of missing data or the alignment between the stated analysis population and the analysis actually conducted.

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 adverse-event summary lists TEST (1,3,5) and TEST (2,4,6) groups, with 49 at risk in each group for serious events and 49 at risk for other events. The reported affected counts are 0 for serious events and 0 for other events in each group. No top serious-event terms are listed. These figures describe the registry's posted event summaries; they are not evidence that no event could occur, nor do they quantify the uncertainty around an event rate.

The registry does not report deaths for either group, so death counts are not reported in the registry record. The adverse-event entries are grouped across TEST (1,3,5) and TEST (2,4,6), rather than presented as separate safety results for each iteration. The record does not explain the event collection period or provide further detail on event definitions in the posted summary. As a result, the figures should be read narrowly as the reported counts for the listed groups, not as a comprehensive comparison of safety between individual lenses.

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

The primary results describe the proportion of embossed lenses meeting a defined axis-position criterion after 3 minutes of wear. They provide a direct snapshot of the posted outcome for TEST1, TEST3, and TEST5. They do not establish that one design is statistically superior to another, because the registry does not report primary confidence intervals, p-values, or an inferential comparison. Nor do they establish that the observed pattern would be reproduced in another sample.

The endpoint is a measurement of lens position relative to an iteration-specific ideal. It is not a direct measure of visual performance, comfort, long-term wear, or a participant's overall experience. The secondary outcomes address awareness and handling on removal, but the registry does not report a formal link between those outcomes and the axis-location measure. These results should therefore be interpreted as distinct summaries rather than as evidence that one outcome explains another.

The study was conducted as a crossover evaluation, with multiple lens iterations worn by participants in a single visit. The posted primary percentages do not show how individual participants' results varied across iterations, or how the order of wear may relate to the measurements. Since the sequence and statistical handling are not reported, the result should not be extended to claims about individual-level consistency or period effects.

Similarly, the short assessment timeframe does not support conclusions about axis orientation over prolonged wear. The brief summary describes approximately 30 minutes of exposure for each pair, while the primary endpoint is specifically after 3 minutes. The registry record does not report later primary assessments. Thus, the results concern an early measurement under the study conditions, not a broader claim about performance over time or in settings beyond the recorded evaluation.

The appropriate interpretation is descriptive and bounded: the registry reports group percentages and secondary summaries from this study, while leaving important comparative uncertainty and analysis details unreported. The results can guide statistical questions for further evaluation, but they do not, on their own, establish a treatment effect or support medical advice.

13. Why This Trial Matters Statistically

This trial illustrates why a clearly named endpoint and a posted numerical result are not enough for a complete statistical interpretation. The primary measure is understandable as a threshold-based percentage, but without confidence intervals or a reported comparison, readers cannot judge the precision of the percentages or the uncertainty in differences among iterations. The distinction between a descriptive pattern and a statistically supported contrast is especially important when several designs are represented.

The crossover structure also highlights the role of design-aware analysis. When the same participant contributes measurements under multiple conditions, statistical methods may need to account for relationships among those measurements. The registry identifies the crossover model but does not report how that structure was incorporated into analysis. This is a useful reminder that the analysis method should correspond to the allocation and measurement structure, and that reporting the method lets readers assess that alignment.

The secondary comparisons and planning illustrations demonstrate another interpretive distinction. Unadjusted comparisons can summarize selected contrasts, while multiple outcomes make isolated p-values less definitive. Planning calculations based on observed effects can be useful as illustrations, but they do not reconstruct the original sample-size rationale or establish observed power. Here, the registry does not report the original design justification or a multiplicity plan.

Finally, the posted outcome count and enrollment figure are not identical, and the record does not explain why. That does not identify a specific data problem, but it does show why clear reporting of analysis populations and missing measurements matters. Together, these features make the study useful for teaching how to separate what the registry directly describes from what would require additional methods, participant-level data, or protocol information.

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.

Several limitations specific to this study constrain interpretation. The primary endpoint is posted only as percentages for the embossed lenses, without the underlying event counts, confidence intervals, or a reported statistical comparison. This leaves both the precision of each percentage and the uncertainty in differences among iterations unquantified. The endpoint is also threshold-based, so the summaries do not show the full range of measured axis deviations.

The registry describes a randomized crossover evaluation with multiple lens pairs worn contralaterally, but does not report the randomized order of iterations or the analysis method. It is therefore not possible to assess whether within-participant dependence, sequence, or period effects were addressed. The posted primary outcome count is 49 in each lens group, compared with enrollment of 50; the record does not explain the difference or report missing-data handling.

The primary measurement is limited to the stated assessment after 3 minutes of wear, despite each pair being worn for approximately 30 minutes. The registry does not report later axis-orientation results. The primary endpoint is restricted to embossed lenses, so it does not provide a primary comparison with the unmarked lenses worn in the opposite eyes. The study's one-visit setting also limits what can be inferred from the posted record about measurements beyond that evaluation.

For secondary outcomes, the registry provides summary statistics and selected unadjusted comparisons but no reported analyses, multiplicity strategy, scale range, or clinically meaningful thresholds. The record also does not provide further details on assessor reliability for slit-lamp evaluation. These are reporting limitations: the registry does not establish that these procedures or analyses were absent, only that they are not reported in the registry record.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: On-Eye Evaluation of Contact Lens Axis Location — NCT02100410.
• Registry record last updated 2014-05-16; status last verified 2014-04.
• Results first posted 2014-05-16.
• 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

NCT02100410 is a completed, randomized, single-masked crossover study sponsored by Alcon Research. Enrollment was 50, with start and primary completion recorded as 2013-04. Participants wore three pairs of delefilcon A toric contact lenses in one visit, with each pair representing a different design iteration.

The primary endpoint was the percentage of embossed lenses within 10 degrees of the ideal axis location after 3 minutes of wear. The registry posts values for TEST1, TEST3, and TEST5, with 49 recorded for each group, but no primary inferential comparison or uncertainty estimates. Secondary outcomes were Lens Awareness and Handling on Removal. The registry also posts adverse-event summaries with zero affected counts in the listed groups, while death counts are not reported in the registry record.