Evaluation of Monthly Replacement Lenses in Habitual Soft Contact Lens Wearers Who Report Frequent Digital Devise Use: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Monthly Replacement Lenses in Habitual Soft Contact Lens Wearers Who Report Frequent Digital Devise Use (NCT05166902), a randomized na study. The primary outcome is Subjective Ratings on Lens Handling on Removal.

2. Clinical Question

The clinical question concerns participants’ subjective experience with lens removal, rather than a clinical examination finding or an objective measure of visual performance. Each participant’s experience with both lenses was relevant to the crossover design, in which the order of lens use varied. The registry record describes one month of wear for each lens and identifies the primary measurement time as day 27.

The posted comparison is a difference in mean ratings between Lens B and Lens A. The reported mean was 8.8 for Lens B and 8.3 for Lens A. These values describe the ratings recorded for each lens in the posted results; they do not by themselves establish how the within-participant responses varied or whether the comparison accounted for the crossover sequence. Details of the primary analysis method are not reported in the registry record.

In statistical terms, the question is whether the observed difference in average ratings is estimated precisely enough to distinguish it from no difference, given the variability in participants’ ratings. That question is distinct from whether the observed ratings are acceptable to any particular participant. The registry record contains no threshold for interpreting the rating difference as meaningful to participants.

3. Trial Design

The registry record describes a randomized, double-masked, crossover trial. Participants were assigned to one of two sequences: Lens A for one month followed by Lens B for one month, or Lens B for one month followed by Lens A for one month. Thus, the planned structure allowed participants to wear both lenses, with sequence allocation determining which was worn first. The record does not report further details about how randomization was generated or concealed, how masking was maintained, or whether a washout period was used.

The lenses were monthly silicone hydrogel devices. Lens A is identified as a comfilcon A lens, and Lens B as a lehfilcon A lens. The registry record describes the target population as habitual soft contact lens wearers reporting frequent digital device use and lists ametropia as the condition. It reports enrollment of 67 participants. For the primary outcome, results are posted for 66 participants for each lens; the reason for the difference between enrollment and the reported outcome counts is not reported in the registry record.

The primary outcome was subjective lens-handling ease on removal, measured at day 27. The registry record lists one outcome measure and no secondary outcomes. It reports the trial as completed, with a start date of 2022-01-31 and a primary completion date of 2022-07-09. The phase is listed as NA.

The registry record identifies CooperVision, Inc. as the sponsor. It does not report the trial’s original sample-size justification, the precise randomization procedure, the planned statistical analysis, or whether the analysis accounted for the repeated observations and treatment sequence inherent in the crossover design. The existence of a crossover design is important context: ratings for the two lenses may be related because the same participants were intended to wear both, but the posted summaries do not describe that relationship.

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: Sixty-seven participants were screened with no screen failures. One participant discontinued and the remaining 66 all completed the study. All the participants who completed the study were included in the analysis. (Analysis population n=66)

First Intervention

Reasons for not completing this period:

Second Intervention

Analysis population for the primary outcome, as defined in the registry: Participants

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: Sixty-six participants completed the study, and demographic data include all participants who completed the study.

6. Primary Endpoint

The registry lists the primary outcome as Subjective Ratings on Lens Handling on Removal, measured over Day 27.

The primary endpoint is a participant’s subjective rating of lens handling on removal at day 27. Ratings use units on a scale from 0 to 10, in 0.5-point steps; 10 is defined as very easy and 0 as very difficult. The registry record describes the population for this measure as participants and summarizes the outcome using a mean and standard deviation for each lens.

This endpoint captures how easy participants felt it was to remove the lens. It is relevant to a comparison of lens designs because handling is part of the wearing experience, and a direct rating can record participants’ perceptions rather than relying only on an observer’s judgment. The scale’s endpoints give the direction of interpretation: higher values indicate easier handling, while lower values indicate more difficulty.

A mean provides a summary of the ratings across participants, while the standard deviation describes how dispersed those ratings were around the mean. Neither measure shows the full distribution of individual responses. In particular, the same mean can arise from different patterns of ratings, and the registry record does not provide a distribution of individual scores or the number of participants selecting each scale value.

The posted mean was 8.3 for Lens A and 8.8 for Lens B. These are descriptive summaries on the stated scale. The record does not identify a threshold for a meaningful difference, nor does it report a separate measure of handling performance such as an objective assessment of removal time or success.

7. Results Posted in the Registry

• Lens B: mean 8.80 versus 8.30 on control; difference 0.50 (95% CI -0.02 to 1.02), standardized effect d = 0.33; z-test p = 0.060.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is a numerical rating measured on a bounded scale. The registry record summarizes it with a mean and standard deviation. The mean is the arithmetic average of participant ratings and gives a central summary. The standard deviation describes how spread out the ratings are around that average. It is not the standard error, and it does not describe the precision of the estimated difference between lenses.

What does the mean difference represent?

The reported comparison is the mean for Lens B minus the mean for Lens A. Its estimate is 0.5 scale units. A positive value means the Lens B average is higher on the scale, whose upper endpoint is defined as very easy. The mean difference is a contrast between group summaries; it is not an estimate of how many participants preferred one lens, and it does not imply that each participant gave Lens B a higher rating.

In a crossover study, participants are intended to receive both conditions in sequence. This can make participant-level comparisons informative because stable differences between people may be controlled by comparing each person with themself. However, the statistical analysis must appropriately account for the pairing and for the order or period in which each lens was worn. General statistical considerations include possible period effects, carryover, and correlation between a participant’s ratings. The registry record does not describe how these considerations were handled, so it is not appropriate to assume a particular crossover model.

What does the confidence interval add?

A confidence interval gives a range of estimates that are compatible with the observed data under the method’s assumptions. The posted interval for the mean difference runs from -0.022 to 1.022 units. Because it includes zero, the interval does not exclude a no-difference estimate. Its lower end also allows a small negative difference, while its upper end allows a larger positive difference than the point estimate. The interval describes uncertainty about the contrast, not the range of ratings from individual participants.

The registry record also posts an unadjusted p-value of 0.06. As a general statistical explanation, a p-value is calculated under a specified null model and assumptions, and it measures how inconsistent the data are with that model. It is not a measure of effect size, a probability that the finding is true, or an assessment of practical importance. Since the registry record does not describe the test used or a prespecified decision rule, the value should be interpreted cautiously and in conjunction with the estimate and interval.

Why does the analysis population matter?

The registry record reports 67 enrolled participants and outcome summaries with 66 participants for each lens. These counts do not identify which participants contributed to each measure, whether observations were paired, or how any missing outcome was handled. In a crossover analysis, knowing whether both period measurements are available for the same participants can be important. The handling of incomplete records, exclusions, and the analysis population is not reported in the registry record.

More generally, analyses may be affected by missingness if participants with unobserved ratings differ from those with observed ratings. The record does not state whether the posted summaries use all randomized participants, participants with outcomes for both lenses, or another defined population. No imputation or sensitivity analysis is described in the registry record.

What can planning calculations tell us?

The planning illustration is based on the observed effect and is not the original design justification. Its stated assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It considers detecting a stated fraction of the observed effect. Under those assumptions, the calculated participant requirements rise as the assumed effect becomes smaller. Such calculations illustrate the relationship between assumed effect size, sample size, and power; they do not reconstruct what investigators planned before the trial.

These planning calculations also do not resolve the crossover-analysis questions. The registry record does not report the original sample-size assumptions, the analysis model, adjustment for repeated measurements, or any interim analysis plan. The posted data support description of the outcome summaries and comparison, but they do not provide enough methodological detail to establish whether the reported inferential analysis followed a prespecified approach.

10. Confidence Intervals and Precision

The estimated mean difference is 0.5 units, with the comparison defined as Lens B minus Lens A. Its confidence interval extends from -0.022 to 1.022 units. The interval is the principal indication of precision in the posted comparison: it displays a range of values compatible with the data under the method’s assumptions, rather than reporting only the single estimate.

Because the interval includes zero, the data are compatible with no mean difference as well as with differences in either direction. The interval also allows positive differences up to 1.022 units. The point estimate is not known without uncertainty; the interval makes that uncertainty explicit. It should not be interpreted as saying that individual ratings fall between its endpoints.

The standard deviations provide additional context about the observed variation in ratings: 1.8 for Lens A and 1.2 for Lens B. They describe spread among ratings, while the confidence interval concerns uncertainty in the estimated difference. The registry record reports 66 participants for each lens summary, but does not explain whether the same participants contributed to both or how the paired nature of a crossover was handled. That missing analytic detail affects how confidently the interval’s calculation can be assessed.

The unadjusted p-value is 0.06, but it does not replace the interval or quantify the magnitude of uncertainty. The registry record does not report a prespecified interpretation threshold or an adjusted result. There is also no reported threshold for a meaningful difference on the rating scale. Thus, the precision can be described statistically, while the practical importance of the range remains undetermined by the registry record.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The sample-size figures are planning illustrations, not observed trial outcomes. They give participants per arm, not total events. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The effect to detect is set to a stated fraction of the observed effect. The original sample-size justification and the trial’s own design assumptions are not reported in the registry record.

For the full observed effect, the planning illustration gives 147 participants per arm for 80% power and 197 participants per arm for 90% power. For planning at 75% of the observed effect, the corresponding figures are 262 and 350 participants per arm. For planning at 50% of the observed effect, they are 588 and 787 participants per arm. The 80% power column describes the planned chance of detecting an effect of the assumed size under the stated model and assumptions when a real effect of that size exists. The 90% column expresses a higher target chance under those same assumptions.

Smaller assumed effects require more participants to achieve the same target power, which explains the increasing planning figures as the assumed fraction decreases. The curve represents this same general relationship between assumed effect size and required sample size; it is not an additional trial result. These calculations are not observed power and should not be used to infer whether the completed trial was adequately powered, because they use the observed effect rather than a documented original design target.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = 0.500; pooled standard deviation σ = 1.530.
2. n = 2 × (1.96 + 0.842)² × 1.530² / 0.500² = 146.9, rounded up to 147 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- 0.5                      # observed difference in means
sigma <- 1.52970585407784                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(5166902)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 147 (80% power), 197 (90% power)
 75% of observed effect: n per arm = 262 (80% power), 350 (90% power)
 50% of observed effect: n per arm = 588 (80% power), 787 (90% power)
power.t.test: 147.9 
Simulated power at n = 147 per arm: 0.800 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry record lists one outcome measure and zero secondary outcomes. It also lists zero posted analyses. The primary endpoint is the day 27 subjective rating of lens handling on removal. Although the outcome count is limited in the registry record, the multiplicity strategy is not reported in the registry record. It is therefore unknown whether any additional outcomes, time points, subgroups, or statistical comparisons were considered in the analysis but not posted.

Multiplicity arises when several hypotheses or outcomes are tested: the chance of at least one apparently notable result can increase as the number of tests grows. Statistical plans may address this through prespecified outcome hierarchies or adjustment procedures. The registry record does not report such a plan or whether the posted p-value was adjusted. It identifies the value as unadjusted, so it should not be treated as an adjusted multiplicity-controlled result.

Missing-data handling is also not reported in the registry record. Enrollment was 67, while the primary outcome summaries list 66 participants for each lens. The record does not identify the reason for the difference, say whether the same participants contributed both lens ratings, or describe any exclusions, imputation, or sensitivity analysis. It also does not state whether participants who lacked an outcome were included in any defined analysis population.

These omissions matter because the validity and precision of a crossover comparison can depend on which participants have measurements in each period and how incomplete pairs are handled. The record does not report whether the analysis used an intention-to-treat population, a per-protocol population, or another population definition. It also does not describe a prespecified statistical analysis plan, interim analyses, or adjustments for period and sequence. In the absence of those details, the posted estimates can be described, but the analysis choices and their effect on the result cannot be evaluated from the registry record.

14. 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.

Most frequent non-serious adverse event terms

The posted serious adverse event figures report zero affected participants for Lens A among 66 at risk and zero for Lens B among 66 at risk. The registry record also reports zero deaths in each group. No serious adverse event terms are listed.

These figures describe the serious adverse events recorded in the registry record for the reported groups. They do not establish that no serious events could occur, and they do not provide a detailed account of surveillance, event definitions, or the time period used for safety collection. The registry record does not give further details about event adjudication or the method used to assign events to a lens period.

The record separately lists other adverse events affecting 4 participants for Lens A and 2 for Lens B, among 66 at risk in each group. These are not serious adverse event counts. Since the trial used a crossover sequence, interpretation of safety by lens may depend on timing and attribution rules; those details are not reported in the registry record. The figures should therefore be read as descriptive registry counts, not as a complete comparative safety analysis or a basis for medical advice.

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

The posted results describe average participant ratings of lens handling on removal at day 27. The average was 8.3 for Lens A and 8.8 for Lens B, and the estimated Lens B-minus-Lens A mean difference was 0.5 units. On the scale used, higher ratings correspond to easier handling. The estimate therefore points toward a higher average rating for Lens B in these posted summaries.

The confidence interval, from -0.022 to 1.022 units, includes no difference and allows values on either side of zero. The unadjusted p-value is 0.06. Taken together, these statistics indicate uncertainty around the size and direction of the mean contrast. They do not establish that one lens is better, and they do not describe what any particular participant experienced.

The result is limited to one subjective endpoint and one stated time point. The registry record does not report a threshold for a meaningful change in handling ratings, the distribution of individual responses, or the number of participants who preferred one lens. It also does not provide secondary outcome results, since none are posted. Accordingly, the mean difference cannot be translated into a claim about the proportion of participants who found removal easier.

The crossover design is relevant because participants were assigned to wear both lenses in different orders, but the registry record does not describe whether the analysis accounted for paired measurements, period, or sequence. Missing-data handling and analysis-population definitions are also not reported. Those details constrain assessment of the inferential comparison. The result is best read as a registry-posted estimate with an interval, rather than as a complete account of the trial’s statistical evidence or its implications for all contact lens wearers.

16. Why This Trial Matters Statistically

This trial illustrates why statistical interpretation requires more than comparing two averages. The primary endpoint is a subjective rating on a scale with defined endpoints, and the posted means differ by 0.5 units. The confidence interval conveys that the estimated contrast is uncertain and includes no difference. Reading the estimate together with its interval avoids treating the point estimate as an exact or definitive result.

The crossover design adds a distinct statistical issue. When participants wear both lenses, ratings from the same participant may be related. That structure can be useful, but it also means that the analysis should reflect repeated observations and the order of treatment. The registry record describes randomization to sequences but does not report how the analysis handled pairing, period, or sequence. This is a practical example of why design information and analysis details need to be considered together.

The posted sample-size illustration also shows how planning depends on the assumed effect size. Smaller effects require more participants under the stated planning assumptions. Because the calculations use the observed effect and do not document the trial’s original design justification, they should not be mistaken for evidence about the adequacy of the completed study.

Finally, the posted outcome and safety summaries are limited records of what was measured and reported. The outcome counts, missing-data approach, multiplicity plan, and analysis population are not fully described. Recognizing these distinctions helps readers separate a descriptive result from a fully documented confirmatory analysis and keeps conclusions appropriately tied to the available evidence.

17. 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 gives limited information about the statistical analysis. It does not report a formal analysis plan, the model used for the primary comparison, or whether the analysis accounted for the crossover design’s within-participant pairing, treatment sequence, or period. It also does not report whether carryover was assessed. These omissions make it difficult to evaluate the assumptions behind the posted interval and unadjusted p-value.

The outcome summaries list 66 participants for each lens, while enrollment is 67. The reason for the difference is not reported in the registry record. The record does not state whether the same participants contributed results for both lenses, how incomplete measurements were handled, or which analysis population was used. Missing-data assumptions and sensitivity analyses are not reported.

The primary measure is a subjective rating at day 27. The registry record does not provide individual-level distributions, participant preference counts, a threshold for meaningful difference, or results for secondary outcomes. It also does not describe the scale’s validation or how the endpoint was selected. Therefore, the practical meaning of the mean difference and the diversity of participant experiences cannot be assessed from the posted summaries.

The sample-size illustration is based on the observed effect and stated planning assumptions, rather than a reported original design justification. The registry record does not report interim analyses or a multiplicity plan. Safety information is limited to the posted adverse-event counts, without further detail on event definitions, timing, or attribution by lens period. These limits do not negate the reported statistics, but they restrict how completely the trial’s design, analysis, and results can be evaluated.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Evaluation of Monthly Replacement Lenses in Habitual Soft Contact Lens Wearers Who Report Frequent Digital Devise Use — NCT05166902.
• Registry record last updated 2023-07-27; status last verified 2022-05.
• Results first posted 2023-07-27.
• 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.

21. Record Summary

NCT05166902 is a completed randomized, double-masked crossover trial sponsored by CooperVision, Inc. It evaluated two monthly silicone hydrogel contact lenses in habitual soft contact lens wearers reporting frequent digital device use. Participants were assigned to wear Lens A and then Lens B, or Lens B and then Lens A, with each lens worn for one month. Enrollment was 67.

The primary endpoint was the day 27 subjective rating of handling on removal, measured from 0, very difficult, to 10, very easy. The posted means were 8.3 for Lens A and 8.8 for Lens B, with an estimated mean difference of 0.5 units and a confidence interval from -0.022 to 1.022. The unadjusted p-value was 0.06.

The registry record lists one outcome measure and zero posted analyses. It reports no serious adverse events or deaths among the listed at-risk participants. Details of the primary analysis, missing-data handling, analysis populations, and original sample-size justification are not reported in the registry record.