The Impact of Contact Lens Coefficient of Friction (CoF) on the Development of Lid Wiper Epitheliopathy (LWE): Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for The Impact of Contact Lens Coefficient of Friction (CoF) on the Development of Lid Wiper Epitheliopathy (LWE) (NCT03209505), a randomized phase 4 study. The primary outcome is Lid Wiper Epitheliopathy.

2. Clinical Question

The clinical question is whether lid wiper epitheliopathy (LWE) grades differ between eyes fitted with contact lenses described as having low versus high coefficients of friction. The registry describes participants fitted with a different lens brand in each eye, with the assignment of lens to eye randomized. The outcome was assessed one week after contact lens fitting.

The outcome is a grade for each eye, rather than a report of symptoms or a participant-level clinical event. The scale ranges from 0 to 3, with higher grades indicating worsening LWE. The registry lists 20 participants enrolled and reports 20 observations for each eye assignment. The posted results therefore describe eye-specific scores, but do not provide an analysis that estimates the difference between the two assignments while accounting for the fact that each participant contributed both eyes.

This distinction matters when reading the question. The registry identifies randomized assignment of the lenses to eyes, but the posted results do not show a test, confidence interval, or other estimate of the between-lens contrast. The results can be summarized descriptively; they do not establish whether the observed summaries differ beyond the uncertainty expected in the study.

3. Trial Design

The registry describes a Phase 4, randomized, double-masked, parallel-model study with an enrollment of 20. Its status is completed. The record gives a start date of 2017-06-26 and a primary completion date of 2018-04-13. The sponsor is the University of Houston.

Participants were fit with two different contact lens brands, one in each eye. The assignment of lens to eye was randomized. Eye 1 was fitted with Acuvue Oasys, described as the low coefficient of friction lens, while Eye 2 was fitted with Air Optix Night & Day Aqua, described as the high coefficient of friction lens. These lens brands are the study interventions listed in the record.

The registered primary outcome is Lid Wiper Epitheliopathy, assessed as staining of the upper eyelid. The primary outcome timeframe is one week post contact lens fitting. The registry describes grading each eye separately on a scale from 0 to 3. The posted summaries include 20 observations for each eye assignment.

The record's parallel-model label appears alongside a description in which each participant receives a different lens brand in each eye. It does not report a separate statistical model or explain how the model label relates to the paired eye observations. The outcome analyses needed to clarify that issue are not posted: the record lists no analyses, and the comparison is identified as not reduced to one comparison.

Some design details cannot be established from the registry record. Eligibility criteria, participant demographics, the intended sample-size justification, and any interim analyses are not reported in the registry record. The masking roles and procedures are also not described beyond the double-masked designation. Those omissions limit how fully readers can assess the planned design or compare it with the posted 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: The study was a contralateral fitting study with one eye receiving the Acuvue Oasys and the contralateral eye receiving the Air Optix Night and Day. Forty eyes of twenty subjects were examined and completed the study

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 Lid Wiper Epitheliopathy, measured over One week post contact lens fitting.

The primary endpoint is lid wiper staining of the upper eyelid, summarized as a grade for each eye. The lid wiper region is described in the registry as the portion of the marginal conjunctival epithelium that moves across the ocular surface or contact lens during blinking. The posted grade scale runs from 0 to 3: none is 0, mild is 0.25 to 1.00, moderate is 1.25 to 2.00, and severe is 2.25 to 3.00. Higher grades indicate worsening LWE.

This endpoint provides a structured way to record the degree of staining at the lid wiper region. A graded outcome retains more detail than a simple present-or-absent classification, but its categories are ordered rather than necessarily equally spaced. The registry reports the primary outcome as a median with an inter-quartile range, a suitable descriptive format for an ordered score that may not follow a symmetric distribution.

Assessment was scheduled one week after contact lens fitting. That timing specifies when the registered outcome was measured; it does not show how scores changed over time, because no baseline outcome or repeated follow-up results are posted. The endpoint is an ocular staining grade, not a direct measure of symptoms, quality of life, or another patient-reported outcome. Such measures are not reported in the registry record.

The registry also lists LWE as a secondary outcome. It does not give a separate secondary result or analysis. The posted primary endpoint summaries should therefore be interpreted as the available descriptive grading results, not as a complete account of every possible clinical outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry reports the primary endpoint as a median and an inter-quartile range. These statistics describe the center and spread of observed scores without requiring a symmetric, bell-shaped distribution. The median is the middle value after observations are ordered. The inter-quartile range describes the interval containing the central half of the data. Here the registry posts the median and the endpoints of that range for each eye assignment.

Why use medians for a graded outcome?

LWE grades are ordered categories on a scale from 0 to 3. The ordering conveys that a higher grade represents worse staining, but it does not by itself guarantee that the step from one part of the scale to another has a constant meaning. A median respects the ordering and can be interpreted as a central grade. The inter-quartile range conveys variation in the observed scores. These summaries are useful descriptions, but they do not show every feature of the underlying score distributions.

In particular, identical or nearby medians can coexist with different distributions, and overlapping inter-quartile ranges are not a formal test of a treatment contrast. Conversely, the relative ordering of two medians is not, by itself, evidence of a statistically reliable difference. To assess a contrast, readers would need an estimate of the difference or another appropriate comparison, together with its uncertainty and the method used to obtain it. None is reported in the registry record.

Why does the eye-level design matter?

The registry describes each participant as wearing a different lens brand in each eye, with lens assignment to each eye randomized. Thus the two eye scores belonging to the same participant may be related. In general, an analysis of paired observations uses the within-participant relationship rather than treating each eye score as independent. This can affect both the estimated uncertainty and the interpretation of a comparison.

The record reports 20 observations under each eye assignment, but it does not post participant-level data or a paired comparison. It also does not describe a statistical model for the relationship between the eyes. Readers therefore cannot determine how any within-participant correlation was handled, or calculate an appropriate paired uncertainty estimate from the summary statistics alone. The registry's parallel-model designation does not supply those missing analysis details.

What does the absence of a comparison mean?

The registry lists no analyses and flags that values are missing or not estimable for a two-arm comparison because the study kind is not reduced to one comparison. This means the posted results support a descriptive account, not an inferential conclusion about the lens contrast. The absence of a p-value does not imply that a test found no difference. The absence of a confidence interval does not imply that uncertainty is small or large; it means the interval is not reported.

A confidence interval, in general, is a range of estimates compatible with the data and the assumptions of the analysis. It is useful because it conveys the precision of an estimated contrast, rather than presenting a binary significance decision alone. No interval for the lens comparison is available. The registry also does not report a test statistic, model, adjustment strategy, or prespecified hypothesis for this endpoint.

What can be inferred from the posted summaries?

The medians and inter-quartile ranges can be read as summaries of the observed scores at one week. They do not indicate how the results would vary in other samples, and do not quantify an effect adjusted for the paired eye structure. A full score distribution would also help describe how often each severity category occurred, but category counts are not posted.

General statistical planning concepts should be kept separate from the observed results. The sample-size illustrations are based on the observed effect and stated assumptions, including a two-sided significance level of 0.05, equal allocation, and a normal approximation. They are hypothetical planning illustrations, not a report of the trial's own design justification, and not observed power. The registry does not report the trial's sample-size justification or its planned statistical analysis. The illustrations cannot repair the missing comparison or establish what the original study was designed to detect.

Over-dispersion is a general concern when outcomes vary more than a chosen statistical model expects: standard errors and tests based on an inadequate variance model can be misleading. The record does not report use of a count model, a variance estimate, or evidence of over-dispersion. This concept is therefore not a claim about this trial's data; it illustrates why conclusions depend on an analysis model that is appropriate to the outcome and design.

Overall, the available statistical information consists of endpoint definitions and descriptive summaries. The methods used to generate the reported summaries, the analysis population, handling of missing observations, and inferential approach are not reported in the registry record. Those details would be needed for a reproducible statistical assessment.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists Lid Wiper Epitheliopathy as the primary outcome and also lists Lid Wiper Epitheliopathy among the secondary outcomes. It reports two outcome measures and one posted secondary outcome, but no analyses are listed. A separate secondary result is not posted. The record does not explain whether the primary and secondary listings refer to distinct timepoints, summaries, or analyses.

Multiplicity arises in general when several outcomes, timepoints, or comparisons are tested: the chance of at least one apparently unusual result can increase as the number of tests grows. A prespecified approach can address that issue, for example by identifying a primary contrast or controlling the family of tests. The registry record does not report a multiplicity plan, a hierarchy of tests, or any adjustment for multiple analyses. Because no inferential analyses are posted, readers cannot assess how multiplicity was handled in practice.

Missing-data methods and analysis populations are also not reported in the registry record. Although the primary summaries list 20 observations for each eye assignment and enrollment is 20, the record does not state whether every enrolled participant contributed outcome data, how missing measurements were handled, or whether the summaries include all randomized participants. No intention-to-treat, per-protocol, or other analysis population is described.

The registry does not report an interim-analysis plan, stopping rules, or a sample-size justification. These details should not be inferred from the completed status or from the posted outcome summaries. In their absence, the reported results can be described, but the reader cannot verify the intended analysis strategy or assess whether the analysis population and missing-data decisions followed a prespecified plan.

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 0% reporting threshold.

The registry's adverse-event figures should be read with attention to their stated denominators. For each eye-assignment group, 10 were listed as at risk for serious adverse events and 0 as affected. The same groups each list 10 at risk for other adverse events and 0 affected. Deaths are listed as 0 in both groups. No serious adverse-event terms are listed.

These are the posted safety counts; they are not the same denominators as the 20 observations reported for each primary endpoint summary. The registry does not explain why the safety figures use 10 at risk in each group, how those safety groups relate to participants or eyes, or whether the counts represent a particular safety analysis population. The difference in denominators should not be resolved by assumption.

Zero affected participants in the listed safety groups means that no events are recorded in those fields for the stated at-risk counts. It does not establish that no events occurred outside the recorded groups or that the study rules out uncommon harms. The record does not describe the safety surveillance period or provide further details about ascertainment. These figures are a limited summary of what was posted, not a complete safety profile.

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

The posted results establish what summaries the registry reports: at one week after fitting, the low-coefficient-of-friction eye assignment had a median LWE score of 0.63 and an inter-quartile range from 0.0 to 1.44; the high-coefficient-of-friction eye assignment had a median of 0.25 and an inter-quartile range from 0.0 to 1.94. Each summary is based on 20 observations. The endpoint scale ranges from 0 to 3, with higher grades indicating worsening LWE.

These figures describe the observed scores. They do not establish that one lens assignment produced a higher or lower outcome in a statistical sense. No comparison estimate, confidence interval, test result, or analysis method is reported. The summaries also do not reveal the number of observations at each grade, and they cannot show whether a contrast would remain after accounting for the paired eyes within participants.

The record does not establish equivalence or absence of an effect. A lack of posted inferential analysis is not the same as an analysis finding no difference. Likewise, the median ordering should not be treated as proof that the lens with the lower posted median has a beneficial effect. The posted results do not support medical advice or a conclusion about an individual's choice of contact lens.

The record is also limited in what it says about generalizability. It reports an enrollment of 20, but eligibility details, participant characteristics, and the intended sample-size justification are not reported in the registry record. The safety counts have a separate at-risk denominator of 10 in each group, and the record does not explain how those groups were defined. Readers should keep the descriptive endpoint summaries and safety counts separate.

In short, the result is an account of eye-specific LWE grades observed at the registered follow-up, not a completed statistical demonstration of a difference between the lens assignments. A fuller conclusion would require a reported comparison that reflects the randomized eye assignment and the within-participant structure, as well as details of the analysis population and missing-data handling.

13. Why This Trial Matters Statistically

This trial is statistically interesting because its intervention is assigned at the eye level while each participant is described as wearing a different lens brand in each eye. That structure creates a natural within-participant comparison, but also means the two eye outcomes cannot automatically be treated as independent. How the pairing is handled is central to estimating uncertainty for a lens contrast.

The registry illustrates a common distinction between descriptive results and comparative evidence. Medians and inter-quartile ranges convey useful information about observed scores, especially for an ordered grading scale. They do not, on their own, answer whether the distributions differ in a way that is statistically distinguishable from sampling variation. The absence of a posted comparison leaves that question unresolved.

The record also highlights the importance of consistent denominators. The primary endpoint summaries each report 20 observations, whereas the adverse-event fields list 10 at risk in each group. Unless the safety population and its relationship to the outcome population are clarified, readers should not combine or casually compare those counts.

Finally, the trial illustrates why a registry's design labels and outcome summaries are not substitutes for a statistical analysis plan and full results. The record identifies randomization, masking, endpoint timing, and the descriptive statistic, but does not report the planned sample-size justification, analysis model, missing-data approach, multiplicity plan, or inferential results. Those details are needed to evaluate precision and reproducibility. The study remains a useful example of how a paired eye-level design calls for careful reporting, even when the main posted result is descriptive.

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 most important limitation of the posted results is the lack of a statistical comparison between eye assignments. No analysis is listed, and no estimate of the contrast, uncertainty interval, or test result is reported. The registry therefore does not provide a basis for inferential conclusions about the lens comparison.

The study description says each participant received a different lens brand in each eye, with assignment randomized to eye. However, the registry does not report participant-level paired data or explain how the relationship between the two eyes was addressed. It identifies the study as parallel-model, but does not give a model specification that clarifies the analysis of paired observations.

The endpoint is summarized with medians and inter-quartile ranges, but full score distributions and counts for the scale's categories are not posted. This limits assessment of the pattern and spread of grades. The registry states a one-week assessment timeframe but does not provide baseline scores or other follow-up measurements, so the posted summaries cannot show change over time.

Other information needed to judge the results is not reported in the registry record: participant eligibility and characteristics, sample-size justification, statistical analysis plan, multiplicity approach, analysis population, and handling of missing outcome data. Safety counts use 10 at risk in each eye-assignment group, while the primary summaries report 20 observations per group; the relationship between those denominators is not explained. The record also does not give details on the safety observation period or adverse-event collection.

These limitations do not alter the reported descriptive values, but they constrain how precisely and broadly those values can be interpreted. The results should be understood as registry summaries rather than a fully documented comparative analysis.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: The Impact of Contact Lens Coefficient of Friction (CoF) on the Development of Lid Wiper Epitheliopathy (LWE) — NCT03209505.
• Registry record last updated 2021-08-31; status last verified 2021-08.
• Results first posted 2021-08-31.
• 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

This completed Phase 4 study, sponsored by the University of Houston, enrolled 20 participants. The registry describes a randomized, double-masked, parallel-model trial in which a different contact lens brand was assigned to each eye: Acuvue Oasys for Eye 1, identified as low coefficient of friction, and Air Optix Night & Day Aqua for Eye 2, identified as high coefficient of friction.

The primary outcome was upper-eyelid lid wiper staining, graded on a scale from 0 to 3, with higher grades indicating worsening LWE. It was assessed one week after fitting. The posted median and inter-quartile range are 0.63 and 0.0 to 1.44 for Eye 1, and 0.25 and 0.0 to 1.94 for Eye 2; each group lists 20 observations.

No statistical analyses are posted, and the registry does not report a comparison estimate or inferential result. Safety fields list 0 serious adverse events, 0 other adverse events, and 0 deaths in each group, with 10 at risk for serious and other adverse events per group. The relationship between those safety denominators and the endpoint observations is not explained.