Performance Comparison of Two Monthly Replacement Silicone Hydrogel Multifocal Lens Types: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Performance Comparison of Two Monthly Replacement Silicone Hydrogel Multifocal Lens Types (NCT06232590), a randomized na study. The primary outcome is Lens Handling for Insertion.

2. Clinical Question

The question is about a participant-reported handling score, rather than a clinical examination or an objective measure of insertion performance. The recorded comparison is between the average ratings for the test and control lenses. The test-lens mean was 96.0 and the control-lens mean was 95.0; the recorded mean difference was 1.0, with the test lens as the higher-scoring lens.

Because participants used both lens types in different sequences, this was a crossover comparison. In principle, such a design can compare lens experiences within participants, while sequence and period effects may also be relevant to interpretation. The registry record does not report how the statistical analysis handled pairing, sequence, or period. It therefore supports describing the recorded summary and comparison, but not a more detailed reconstruction of the analysis.

3. Trial Design

The registry describes a randomized, single-masked, crossover study of two monthly replacement silicone hydrogel multifocal lens types. Enrollment was 60, and the record lists the study status as completed. The recorded start date was 2024-02-23 and the primary completion date was 2024-07-09. The sponsor was CooperVision International Limited (CVIL).

Participants were assigned to one of two sequences. In one sequence, participants wore the control lens for 1 month and then the test lens for 1 month. In the other, participants wore the test lens for 1 month and then the control lens for 1 month. The control lens was comfilcon A and the test lens was lehfilcon A. The registry summary describes the participants as existing wearers, and lists presbyopia as the condition.

Randomization assigns participants to the order in which they receive the lens types. This can help balance sequence assignment, but it does not by itself establish how the investigators addressed other features of a crossover design. The identity of the masked party, details of random-sequence generation, allocation concealment, any washout period, and procedures for handling possible carryover are not reported in the registry record.

The primary endpoint summaries list 59 observations for each lens. The registry record does not explain why the analysis counts differ from the enrollment figure, whether any participants did not contribute a score for one or both periods, or how missing measurements were handled. It also does not describe the analysis population or provide a participant flow account. These omissions limit assessment of how the recorded outcome summaries relate to the randomized sequences.

The record lists one outcome measure and no posted secondary outcomes. It does not report the trial’s original sample-size rationale or detailed statistical analysis plan. The planning illustration associated with the observed comparison is not evidence about the assumptions used to design or conduct this trial.

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: First Intervention

Period 2: Second Intervention

Reasons for not completing this period:

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 Handling for Insertion, measured over 1 month.

The primary endpoint is “Lens Handling for Insertion,” measured as a participant’s subjective rating on a 0-100 scale. A rating of 0 represents very difficult insertion and a rating of 100 represents very easy insertion. The participant considered a typical day in the last 1 month of wearing the study lens, and the rating was collected in office.

This measure captures the wearer’s experience of a practical task associated with lens use. A high score corresponds to a more favorable ease-of-insertion rating on the defined scale. The endpoint is therefore directly relevant to the specific handling question being asked, but it should not be read as a measure of other aspects of lens performance, such as vision, comfort, or clinical outcomes; those are not the primary outcome described in the registry record.

The registry reports the mean and standard deviation for each lens. The control-lens mean was 95.0, with a standard deviation of 9.0; the test-lens mean was 96.0, with a standard deviation of 8.0. The recorded timeframe is 1 month. The record does not report a threshold for a meaningful difference in this rating, so the numerical result alone cannot establish whether a difference would matter to participants in practice.

As a general statistical point, a mean describes the average score, while a standard deviation describes how dispersed individual scores are around that average. Neither quantity shows the full distribution of ratings or explains why participants gave the ratings they did. The registry record does not provide those individual-level details.

7. Results Posted in the Registry

• Test Lens: mean 96.00 versus 95.00 on control; difference 1.00 (95% CI -2.07 to 4.07), standardized effect d = 0.12; z-test p = 0.524.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: each participant’s insertion-handling experience is represented by a score on a 0-100 scale. The registry reports a mean and standard deviation for each lens, then a mean difference with a confidence interval and unadjusted p-value. The mean difference is reported as 1.0, with the test-lens mean higher than the control-lens mean. This is a description of the recorded comparison, not a new calculation.

What does the mean describe?

In general, the mean is the arithmetic average of the recorded scores in a group or condition. It gives a compact description of the center of the scores, but it can conceal variation among participants. The reported means were 95.0 for the control lens and 96.0 for the test lens. Since the scale defines larger values as easier insertion, the direction of the recorded mean difference favors a higher ease rating for the test lens. The registry does not report a threshold for interpreting the size of that difference as important.

The standard deviations were 9.0 for the control lens and 8.0 for the test lens. In general, a standard deviation describes how widely scores vary around their mean. It is not a confidence interval for the mean, and it does not describe the uncertainty in the mean difference by itself. In a crossover trial, the correlation between the same participant’s scores under the two lenses can affect the uncertainty of a paired comparison. That correlation is not reported in the registry record.

What does the confidence interval add?

In general, a confidence interval combines an estimate with information about its precision. Under repeated use of the same method and assumptions, intervals at a stated confidence level are designed to cover the underlying parameter at the corresponding long-run rate. The recorded 95% confidence interval for the mean difference extends from -2.073 to 4.073. It includes zero and values on both sides of zero. This means the reported data do not pinpoint the direction of the difference with high precision.

The interval should be interpreted alongside the design and analysis method. The registry record does not specify whether the interval comes from a paired analysis, a model that accounts for period and sequence, or another approach. It also does not provide enough detail to reproduce the interval from participant-level observations. Accordingly, the interval describes the comparison as recorded, while its underlying model assumptions are not fully documented in the registry.

How should the p-value be read?

The unadjusted p-value is 0.524. In general, a p-value is calculated under a null hypothesis and a statistical model; it describes the frequency of results at least as incompatible with that null model as the observed result, if the model and null hypothesis apply. It is not a measure of the probability that the observed result happened “by chance,” and it does not measure clinical importance. A p-value does not replace the estimate and interval, which convey direction, scale, and precision.

The registry does not report whether the p-value is based on a paired test, a crossover model, or another method. The term “unadjusted” indicates that the posted value is not presented as adjusted for multiplicity. It does not tell the reader which covariates, periods, sequences, or other design features were included. Those analytic details are not reported in the registry record.

Why does crossover structure matter?

General explanation: in a crossover study, participants receive more than one treatment or intervention in sequence. The analysis may use within-participant comparisons, which can account for stable differences between participants. Period effects, sequence effects, and carryover from an earlier period may also be relevant. Randomization of order can help address sequence assignment, but it does not itself show which model was fitted or how these effects were handled. The registry record reports the two sequences and their duration, but does not report a washout period or the statistical approach to period and carryover.

The registry reports 59 observations for each lens. It does not report whether all observations came from participants with ratings in both periods, how incomplete pairs were handled, or which participants were included in the analysis. The distinction matters because an analysis based on paired observations and one that treats the lens summaries as independent may use different information and uncertainty assumptions. No individual-level data or detailed analysis population description is reported.

What does over-dispersion mean in general?

General explanation: over-dispersion occurs when observed variability is greater than a statistical model expects. It is a concern in some count-data models, where it can make standard errors and confidence intervals too small if ignored. This endpoint is a continuous rating summarized by means and standard deviations, and the registry record does not report an over-dispersion analysis. That concept is not a substitute for the more directly relevant questions about pairing, period, missingness, and model specification in this crossover comparison.

The registry lists one outcome measure and no posted secondary outcomes. It does not report a complete statistical analysis plan, the original sample-size justification, any interim analyses, or adjustments for multiple comparisons. Those details should not be inferred from the reported p-value or from the separate planning illustration.

10. Confidence Intervals and Precision

The recorded mean difference is 1.0, with a 95% confidence interval from -2.073 to 4.073. The estimate gives the central value of the comparison, while the interval communicates uncertainty around it under the method used. The interval includes zero and spans negative and positive differences. Thus, the posted comparison does not resolve whether the test-lens mean is lower or higher than the control-lens mean in the population represented by the analysis.

In general, a narrower interval indicates greater precision, while a wider interval indicates more uncertainty about the estimate. Precision is not the same as importance: even a precise estimate may be too small to matter, and an imprecise estimate may include differences that would matter in either direction. The registry record does not give a participant-important threshold for the insertion-handling score, so the interval cannot be classified against such a threshold.

The interval’s interpretation also depends on the statistical method and analysis population. This was a crossover design, but the registry record does not report whether the comparison accounted for within-participant pairing, period, or sequence. Nor does it report how missing ratings were handled. Those omissions make it difficult to assess whether the reported precision reflects the design’s paired structure or which observations contributed to the comparison.

The standard deviations of 9.0 for the control lens and 8.0 for the test lens describe score variability, not the precision of the mean difference. The record does not provide the within-participant correlation or individual ratings, so the uncertainty cannot be independently reconstructed from the posted summaries alone. The confidence interval and p-value should therefore be read as the registry’s recorded comparison, with the analytic details not reported in 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 planning illustration reports participants per arm for 80% power and participants per arm for 90% power. These are planning estimates based on the observed effect, not observed power. They are not a report of the number enrolled in this crossover trial or a statement of the trial’s original design target.

The listed assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The target effect is set to a stated fraction of the observed effect. The registry record does not report the assumptions used for the trial’s original design or sample-size justification; the illustration is explicitly computed from the observed effect instead.

For 100% of the observed effect, the estimate is 1,139 participants per arm for 80% power and 1,524 participants per arm for 90% power. For 75% of the observed effect, the estimates are 2,024 participants per arm for 80% power and 2,709 participants per arm for 90% power. For 50% of the observed effect, they are 4,553 participants per arm for 80% power and 6,095 participants per arm for 90% power. The rows illustrate that smaller assumed effects require more participants to detect under the stated assumptions.

In general, power is the probability that a specified analysis will reject its null hypothesis when a particular effect is true, under the assumptions used for planning. The 80% and 90% columns represent different target probabilities for detecting the assumed effect. They do not say what probability this completed trial had of finding an effect, and the figures should not be interpreted as observed power. The estimates are per arm, not total event counts; the registry’s general note distinguishes these continuous-outcome figures from time-to-event planning figures, which use total events.

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 = 1.000; pooled standard deviation σ = 8.515.
2. n = 2 × (1.96 + 0.842)² × 8.515² / 1.000² = 1,138.1, rounded up to 1,139 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 <- 1                      # observed difference in means
sigma <- 8.5146931829632                     # 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(6232590)
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 = 1,139 (80% power), 1,524 (90% power)
 75% of observed effect: n per arm = 2,024 (80% power), 2,709 (90% power)
 50% of observed effect: n per arm = 4,553 (80% power), 6,095 (90% power)
power.t.test: 1139 
Simulated power at n = 1,139 per arm: 0.797 (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, the primary endpoint for lens handling for insertion, and no posted secondary outcomes. It reports an unadjusted p-value for the primary comparison. The record does not report a multiplicity-adjustment procedure or a complete analysis plan describing how multiple outcomes or analyses, if any, were to be handled. With no secondary outcomes posted, the reported result should be understood as the comparison recorded for this endpoint, not as evidence about unreported outcomes.

Multiplicity is a general statistical issue that arises when several hypotheses are tested. If many tests are conducted, the chance of at least one apparently notable result can increase unless the analysis plan accounts for that testing. The registry’s listing of a single outcome measure does not establish whether additional analyses were planned or conducted. The registry record lists no analyses, while separately recording the arm summaries and comparison; it does not explain the relationship between those entries.

Missing-data details are also not reported. The outcome summaries list 59 observations for the control lens and 59 for the test lens, while the enrollment figure is 60. The record does not explain the difference, state whether measurements were missing, describe reasons for any missing scores, or specify how missing data were treated. It does not report whether observations were paired for every participant contributing to the comparison.

The analysis population is not described in the registry record. It is therefore not possible to determine from the record whether the comparison included all randomized participants, only participants who completed both periods, or another defined set. The record also does not describe whether protocol deviations affected inclusion, or whether sensitivity analyses assessed missing outcomes.

These omissions do not invalidate the posted summary, but they limit independent assessment of the analysis. In particular, the crossover structure makes information about paired observations and period handling useful for understanding the estimated difference and its uncertainty. The registry record does not report those methods, and they should not be inferred from the numerical result.

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 registry record lists no serious adverse events for either lens. For the control lens, 0 serious adverse events affected participants among 60 at risk; for the test lens, 0 affected participants among 59 at risk. The record lists 0 deaths for each lens. It also lists 4 participants affected by other adverse events among 60 at risk for the control lens and 4 among 59 at risk for the test lens.

These are the recorded counts and at-risk denominators. They do not provide details about the type, timing, duration, severity, or relatedness of the other adverse events. The registry lists no serious adverse-event terms. The record does not explain the at-risk denominator difference between lenses or how adverse events were assigned and counted within the crossover periods.

Zero recorded serious events is not proof that serious events cannot occur, and the adverse-event summaries alone do not establish comparative safety. The counts should be interpreted as descriptive registry data for this study, with the limited event detail and follow-up information reported in the registry record.

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

The result describes how participants rated insertion handling for two monthly replacement multifocal lenses after the recorded 1-month timeframe. The average score was 95.0 for the control lens and 96.0 for the test lens, on a scale where higher values mean easier insertion. The registry’s mean-difference estimate was 1.0, and its 95% confidence interval ranged from -2.073 to 4.073. The recorded unadjusted p-value was 0.524.

These data show high average ratings for both lenses and a small difference between the reported means. The interval includes no difference and possible differences in either direction. The record does not report a threshold for a meaningful change in the score, so the numerical difference cannot be translated into a claim about practical importance. The p-value is not a probability that either lens is superior, and the result does not establish equivalence.

The finding applies to this participant-reported insertion-handling endpoint as recorded. It does not answer questions about visual performance, comfort, other handling tasks, longer-term use, or outcomes in populations beyond the existing wearers described in the registry summary. The registry lists presbyopia as the condition but does not report further detail about the participants or eligibility criteria.

The crossover design means participants used both lens types in a specified order. The registry reports the sequences but does not report whether the comparison accounted for paired measurements, period, or sequence, or whether there was a washout period. It also does not explain the outcome analysis counts or report missing-data methods. These gaps mean the result should be read as the posted comparison, without assuming an undocumented analysis method.

The safety record lists no serious adverse events and no deaths, with other adverse events recorded for each lens. Those descriptive counts are not enough to establish comparative safety, particularly because event details and handling across crossover periods are not reported. Overall, the posted evidence is limited to the summarized insertion ratings and adverse-event counts, with no basis for claims about broader lens performance.

16. Why This Trial Matters Statistically

This trial is statistically interesting because it uses a crossover design to compare two lenses that participants wore in sequence. Such designs can make within-participant comparisons possible, which may be useful when the outcome is a subjective rating and each participant can experience both lens types. But the value of that design depends on how the analysis handles paired observations, treatment order, period effects, and possible carryover. The registry record reports the sequences but not those analytic details.

The reported insertion scores are near the top of the defined scale for both lenses. That context matters for interpretation: a difference in means has to be understood in relation to the scale, the observed spread of ratings, and a threshold for meaningful change. The standard deviations are reported, but a threshold for participant-important difference is not. High averages alone do not establish that the lenses are interchangeable or that scores cannot differ meaningfully for some participants.

The comparison also illustrates why estimates and confidence intervals are more informative than a p-value alone. The point estimate is 1.0, while the confidence interval extends from -2.073 to 4.073 and includes zero. The interval conveys uncertainty about direction and size; the unadjusted p-value of 0.524 is not a measure of practical significance.

Finally, the registry’s planning illustration uses the observed effect and stated hypothetical assumptions, rather than documenting the study’s original design rationale. Keeping planning estimates separate from the trial’s actual design and results prevents a retrospective illustration from being mistaken for evidence of observed power or a prespecified target.

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 crossover analysis. It does not say whether the estimate and confidence interval account for within-participant pairing, period, sequence, or possible carryover. It does not report a washout period or identify who was masked under the single-masked designation. These details affect how the design and comparison can be assessed.

The endpoint is subjective and collected in office. Although the scale anchors and timeframe are described, the registry does not report the exact wording or administration procedures beyond the general description, nor does it give individual ratings or their distribution. A meaningful-difference threshold is not reported, making it difficult to determine how the numerical difference relates to participants’ perceptions.

The analysis counts are 59 for each lens, whereas enrollment is listed as 60. The record does not explain this, describe participant flow, identify the analysis population, or report missing-data handling. It is also unclear whether every participant contributed ratings under both lenses. This limits interpretation of the summaries in the context of the randomized sequences.

The registry reports one outcome measure and no posted secondary outcomes. It does not report the original sample-size rationale, full statistical analysis plan, or any interim analyses. The planning illustration is based on the observed effect under stated hypothetical assumptions and cannot fill those gaps.

Safety information is also brief: serious-event counts, other-event counts, at-risk denominators, and deaths are listed, but details of the other events and their timing or relatedness are not reported. The record therefore supports only a narrow description of the recorded handling outcome and adverse-event summaries.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Performance Comparison of Two Monthly Replacement Silicone Hydrogel Multifocal Lens Types — NCT06232590.
• Registry record last updated 2025-02-12; status last verified 2024-11.
• Results first posted 2025-02-12.
• 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

The registry record describes a completed randomized, single-masked crossover study comparing a control monthly replacement silicone hydrogel multifocal lens, comfilcon A, with a test lens, lehfilcon A. Participants wore each lens for 1 month in one of two sequences. The registry summary identifies existing wearers with presbyopia and lists enrollment of 60.

The primary endpoint was a subjective 0-100 rating of ease of insertion, considering a typical day in the last 1 month of wear. The control-lens mean was 95.0 and the test-lens mean was 96.0. The recorded mean difference was 1.0, with a 95% confidence interval from -2.073 to 4.073 and an unadjusted p-value of 0.524.

The registry lists no serious adverse events and no deaths for either lens, and records other adverse events affecting 4 participants for each lens. It does not report detailed crossover-analysis methods, missing-data handling, an analysis population, or the trial’s original sample-size assumptions.