Clinical Performance Assessment of a Daily Wear Monthly Replacement Soft Silicone Hydrogel Contact Lens: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Performance Assessment of a Daily Wear Monthly Replacement Soft Silicone Hydrogel Contact Lens (NCT04055519), a randomized na study. The primary outcome is Distance VA (logMAR) With Study Lenses.

2. Clinical Question

This is a product-performance assessment, not a treatment trial for a disease outcome. The stated purpose was to obtain on-eye performance data to inform contact lens product development. Visual acuity was measured for each eye individually with study lenses in place, at a distance of 4 meters using a letter chart. The record does not describe a separate clinical threshold for a meaningful difference in logMAR, nor does it report a prespecified superiority or equivalence objective. The result therefore addresses the observed visual-acuity summaries and their statistical uncertainty, rather than establishing that the products are equivalent or that either has a clinically important advantage.

3. Trial Design

This was a randomized, single-masked, crossover study of daily-wear monthly replacement soft silicone hydrogel contact lenses. The registry lists the study as completed, with enrollment of 36. The start date was 2019-09-19 and the primary completion date was 2019-12-03. The sponsor was Alcon Research. The listed phase was NA, which is not a drug-phase designation for this device study.

Participants were randomized to a sequence: lehfilcon A followed by comfilcon A, or comfilcon A followed by lehfilcon A. Each product was intended to be worn in both eyes for 30 days, at least 8 hours a day and 5 days a week. Lenses were to be removed nightly for cleaning and disinfection. Multi-purpose disinfection solution is also listed as an intervention. The registry does not report further details of masking, such as which groups were masked, or the method used to generate or implement the random allocation.

A crossover design means that each participant is scheduled to receive both products in sequence, so comparisons can potentially account for stable differences between participants. That design can be useful when outcomes are measured under both products in the same people. However, the registry record does not report a washout period, sequence-specific outcome summaries, or the method used to handle within-person or within-eye correlation. It also does not report whether the posted summaries combine observations from both eyes in a particular way. Those omissions prevent a detailed assessment of whether the comparison used the crossover structure as intended.

The record lists the primary outcome as distance VA with study lenses, measured at Day 30 after a minimum of 6 hours of wear for each product. The analysis population is described as all subjects and eyes exposed to any study lenses evaluated in the study. The reported number for each product is 36. The interpretation of that denominator as participants, eyes, or another analysis unit is not further clarified 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: This reporting group includes all randomized subjects/eyes (36/72) as treated. Note: Two subjects received investigational product misallocations and were exposed to the incorrect study product in the sequence.

First Wear Period (30 Days)

Second Wear Period (30 Days)

Analysis population for the primary outcome, as defined in the registry: This analysis population includes all subjects/eyes exposed to any study lenses evaluated in this 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.

Population: This analysis population includes all subjects exposed to any study lenses evaluated in this study.

6. Primary Endpoint

The registry lists the primary outcome as Distance VA (logMAR) With Study Lenses, measured over Day 30 after a minimum of 6 hours of wear, each product.

The primary endpoint was distance visual acuity (VA) with study lenses, recorded in logarithm minimum angle of resolution, or logMAR. VA was assessed for each eye individually while the study lenses were in place. Measurement used a letter chart at a distance of 4 meters. The stated timeframe was Day 30 after a minimum of 6 hours of wear for each product.

LogMAR gives a numerical scale for visual acuity. The registry explains that a value of 0 equates to 20/20 Snellen visual acuity, described as normal distance eyesight, and that a lower logMAR value indicates better visual acuity. Thus, in the reported means, a more negative value is in the direction of better measured acuity. The observed values were -0.13 for LID017569 and -0.14 for Biofinity.

Visual acuity is used as a direct measure of distance vision while wearing the lenses, matching the study’s stated purpose of gathering on-eye performance data. The endpoint is continuous, and the registry reports its mean and standard deviation for each product. This supports a descriptive comparison of average measured acuity and the spread of observations. The record does not report a clinically meaningful difference threshold, a responder definition, or a rationale for selecting this endpoint beyond the stated performance-assessment purpose. It also states that no formal hypothesis testing was planned. Consequently, the endpoint results describe measured visual acuity at the specified visit and do not by themselves establish a clinically important difference between products.

7. Results Posted in the Registry

• Biofinity: mean -0.14 versus -0.13 on control; difference -0.01 (95% CI -0.04 to 0.02), standardized effect d = -0.17; z-test p = 0.480.

8. Statistical Interpretation

9. Statistical Methods Explained

The reported endpoint is continuous: distance visual acuity measured in logMAR. A continuous outcome can take a range of numerical values, so the registry summarizes it using a mean and standard deviation. The mean describes the average recorded value in a group. The standard deviation describes how dispersed individual observations are around that group mean. Here, the mean was -0.13 with a standard deviation of 0.06 for LID017569, and -0.14 with a standard deviation of 0.06 for Biofinity.

The direction of the scale matters for interpretation. The registry states that lower logMAR values indicate better visual acuity, with 0 corresponding to 20/20 Snellen visual acuity. Thus a more negative mean is numerically in the direction of better acuity. The difference reported for Biofinity relative to LID017569 is -0.01 logMAR. This is an unadjusted difference in group means, not a separately adjusted estimate accounting for a particular set of covariates or for the crossover sequence.

A confidence interval expresses uncertainty around an estimated quantity. In general, it describes a range of values reasonably compatible with the data and the method used to calculate the interval. The interval for the mean difference is -0.038 to 0.018. Since it includes zero, the data summarized by this interval do not rule out zero difference under the calculation used. The interval also includes values on both sides of zero, corresponding to possible differences in either direction. A confidence interval does not provide a probability that a particular treatment effect is true, and its clinical interpretation depends on whether the values it spans are meaningful for the outcome. A clinical threshold is not reported in the registry record.

The registry reports an unadjusted p-value of 0.48. In general, a p-value summarizes how incompatible observed data are with a specified null model, under the assumptions of the test. It is not the probability that the null hypothesis is true, and it does not quantify the size or clinical importance of a difference. In this study, the registry explicitly states that no formal hypothesis testing was planned. The p-value should therefore be treated as a descriptive unadjusted comparison rather than as the result of a planned primary test.

What does the crossover structure imply?

In general, a crossover design exposes participants to more than one study condition in a randomized order. If the same participant contributes measurements under both conditions, comparing within-participant outcomes can reduce the influence of stable differences between people. But the validity and precision of a crossover estimate depend on the analysis accounting appropriately for the repeated observations and on relevant design features, such as period and sequence. The registry lists randomized sequences, but does not report the statistical model, a washout period, or any analysis of period or sequence effects. It is therefore not possible to determine from the record whether the displayed comparison uses paired data or how the crossover structure was incorporated.

Both eyes were to receive each product, and the outcome description says VA was collected for each eye individually. The registry’s population description includes subjects and eyes, while each arm’s displayed count is 36. The method for combining or modeling two eyes from the same participant is not reported in the registry record. In general, measurements from the same person may be correlated; treating correlated observations as independent can make uncertainty estimates misleading. Without the analysis details, the reported comparison should be read as the registry’s displayed summary rather than as a fully specified eye-level or participant-level model.

What does the standard deviation tell the reader?

The standard deviation of 0.06 in each product group is a measure of observed variability, not a measure of precision of the difference. Precision also depends on the amount and structure of data, including whether observations are paired or clustered. The standard error values listed for the group means are 0.01 for each product, but the record does not explain their derivation or the handling of repeated eyes. The interval around the difference offers a direct summary of uncertainty for the displayed contrast.

Why does the analysis plan matter?

Prespecification helps distinguish planned inferential analyses from calculations made to describe posted summaries. The registry states that no formal hypothesis testing was planned. The record does not report a detailed statistical analysis plan, adjustment variables, missing-data method, or a prespecified clinically meaningful difference. These details matter when assessing whether a statistical comparison addresses the study’s original objectives and whether its uncertainty is calculated in a way that respects the design.

In general, over-dispersion means that data vary more than a model’s assumptions allow. It is especially relevant for count outcomes and some generalized models; it is not a reported feature of this continuous VA endpoint. No over-dispersion assessment is reported for this study, and none can be inferred from the mean and standard deviation alone.

10. Confidence Intervals and Precision

The unadjusted mean difference is -0.01 logMAR, with a confidence interval from -0.038 to 0.018. The interval crosses zero, so it includes no difference in the group means. It also spans values in both directions: negative values correspond to a lower mean with Biofinity under the reported subtraction, while positive values correspond to a higher mean with Biofinity. Since lower logMAR indicates better acuity, the direction of a numerical difference can be interpreted using that scale definition, but the registry does not report a threshold for clinical importance.

The interval communicates more than the point estimate alone. The point estimate is one value derived from the observed summaries; the interval illustrates that the estimate is uncertain. The range is compatible with more than a single exact effect, and its inclusion of zero means that the posted comparison does not clearly distinguish a difference from no difference using that interval. This does not prove the products are equivalent. Establishing equivalence would require a prespecified margin and an analysis designed to assess whether the uncertainty lies within that margin; neither is reported in the registry record.

In general, confidence-interval width depends on the amount of information and the variability of the data, as well as the analysis method. Here, the standard deviation is 0.06 for each product and the reported sample size is 36 for each. Because the design is crossover and both eyes were assessed, the way observations were paired or clustered would also be relevant to precision. Those details are not reported in the registry record, so the interval should be interpreted as the displayed unadjusted interval, without assuming a particular model for the repeated measurements.

The unadjusted p-value is 0.48, but it does not substitute for the interval. The interval gives a range of plausible mean differences on the outcome scale, whereas the p-value condenses a comparison relative to a null model. Neither alone indicates whether a difference is important to users of the lenses. The record does not report a minimum clinically important difference. The precision is therefore best described as an estimate centered near zero with uncertainty extending to either side, rather than as proof of no difference or proof of a particular product advantage.

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 figures are participants per arm, not total events. They are illustrative calculations based on the observed effect, not the original design assumptions for this trial. The listed planning 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 at the stated fraction of the observed effect. The trial’s own original sample-size assumptions and justification are not reported in the registry record.

The 80% power column gives the number of participants per arm that the planning calculation estimates would be needed to have an 80% chance of detecting the chosen effect under those assumptions, if that effect were present and the model assumptions held. The 90% power column expresses the corresponding planning target for a 90% chance. These are design-planning quantities, not descriptions of what happened in the completed study. The figures are not observed power.

The rows illustrate planning for 100%, 75%, and 50% of the observed effect. For example, planning for 100% of the observed effect gives 566 participants per arm for 80% power and 757 participants per arm for 90% power. Planning for 50% of the observed effect gives 2,261 participants per arm for 80% power and 3,027 participants per arm for 90% power. A smaller effect is harder to distinguish from random variation, so it requires more participants under the same planning assumptions. The displayed calculations are not a recommendation for a future trial and do not establish that the present study was adequately or inadequately powered.

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 = -0.010; pooled standard deviation σ = 0.060.
2. n = 2 × (1.96 + 0.842)² × 0.060² / -0.010² = 565.1, rounded up to 566 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 <- -0.01                      # observed difference in means
sigma <- 0.06                     # 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(4055519)
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 = 566 (80% power), 757 (90% power)
 75% of observed effect: n per arm = 1,005 (80% power), 1,345 (90% power)
 50% of observed effect: n per arm = 2,261 (80% power), 3,027 (90% power)
power.t.test: 566.1 
Simulated power at n = 566 per arm: 0.799 (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 lists one primary outcome measure: distance VA in logMAR with study lenses. It states that no formal hypothesis testing was planned. No secondary outcome measures are posted in the record. The record does not report a multiplicity strategy, such as adjustment for multiple endpoints, comparisons, time points, or subgroup analyses. With only the listed primary endpoint, multiplicity cannot be assessed beyond noting that no adjustment method is described.

The registry also does not report a detailed statistical analysis plan. In particular, the method used to account for the randomized crossover sequence, repeated product periods, two eyes per participant, or possible period effects is not reported in the registry record. The presence of a comparison between product means does not establish that a paired or crossover-specific inferential model was used. The record does not report covariate adjustment or a predefined hierarchy of analyses.

Missing-data methods are not reported in the registry record. There is no description of how missing VA measurements, incomplete product periods, withdrawals, or unusable eye-level assessments were handled. The displayed count of 36 for each product does not by itself show whether all scheduled measurements were available, how missing observations were treated, or whether the same participants contributed to both product summaries.

The primary population is described as all subjects and eyes exposed to any study lenses evaluated in the study. The registry does not provide a further definition of analysis sets, such as an intention-to-treat population or a per-protocol population. It also does not report a participant flow accounting for exclusions from the endpoint analysis. As a result, the scope of the reported summaries can be described using the registry’s stated population, but the details needed to reproduce the analysis or evaluate the consequences of missing data are not available.

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 5% reporting threshold.

The safety record lists serious adverse events, other adverse events, and deaths for pre-treatment and product-specific groups. In the pre-treatment group, 36 were at risk for serious adverse events and 36 for other adverse events; zero serious events and zero other events were recorded, with zero deaths. For LID017569 ocular events, 72 were at risk in each adverse-event category, with zero serious events, zero other events, and zero deaths. For LID017569 nonocular/systemic events, the at-risk count was 36 in each category, with zero events and zero deaths.

For Biofinity ocular events, 72 were at risk in each category, with zero serious events, zero other events, and zero deaths. For Biofinity nonocular/systemic events, 36 were at risk in each category, with zero events and zero deaths. The registry lists no top serious adverse-event terms.

These are the recorded counts for the listed groups and at-risk denominators. The record does not clarify whether the ocular denominator represents eyes or another unit, so it should not be interpreted as a count of participants. Zero recorded events means none were listed in these registry categories; it does not establish that no events occurred outside the recorded definitions or observation periods. The registry does not report further information on event collection, severity grading, or attribution.

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

The results describe distance visual acuity measured with the study lenses at Day 30 after a minimum of 6 hours of wear for each product. The mean was -0.13 logMAR for LID017569 and -0.14 logMAR for Biofinity, with a standard deviation of 0.06 for each. Given that lower logMAR indicates better acuity, the observed mean for Biofinity is numerically lower. The unadjusted difference is -0.01 logMAR, and its confidence interval extends from -0.038 to 0.018.

Those summaries support a limited statement: the observed group means were close, and the displayed interval includes zero as well as differences in either direction. They do not establish that the products are equivalent. Equivalence requires a defined margin and an analysis designed for that question; neither is reported. The record also provides no clinical threshold for deciding whether a difference in logMAR would matter to participants or clinicians.

The unadjusted p-value of 0.48 should not be interpreted as proof of no difference. It summarizes the comparison relative to a null model, but the registry says no formal hypothesis testing was planned. Nor does that value indicate the probability that either product is better. The confidence interval and point estimate provide the more direct description of the magnitude and uncertainty of the displayed mean difference.

The study’s randomized crossover design and inclusion of measurements from each eye are relevant to how the estimate should be analyzed. Yet the record does not report the model, the handling of within-participant or within-eye correlation, sequence or period effects, or missing measurements. Those limitations mean the posted summaries cannot answer every design-based question. They also do not support conclusions about outcomes beyond the stated distance-VA measure, timeframe, and study population. The registry’s stated purpose was to obtain on-eye performance data to inform contact lens product development, and the results should be interpreted within that scope.

16. Why This Trial Matters Statistically

This trial illustrates why a numerical difference, its uncertainty, and the analysis plan need to be considered together. The reported means are -0.13 and -0.14 logMAR, while the unadjusted mean difference is -0.01. The difference’s confidence interval, -0.038 to 0.018, includes zero and values in either direction. That context is more informative than focusing on the point estimate or p-value alone.

The crossover structure is also statistically important. Because participants were assigned to wear both products in sequence, an analysis may need to account for repeated measurements within people and possibly within eyes. Such design-aware analysis can affect both the estimated comparison and its precision. The registry does not report how those dependencies were handled, so readers cannot assess whether the posted comparison uses the full structure of the study.

The record’s statement that no formal hypothesis testing was planned is essential context for the unadjusted p-value. It discourages treating that value as a prespecified decision rule. The absence of a reported clinical difference threshold also means that statistical uncertainty cannot be translated into a judgment about practical importance. These are distinct questions: what the data estimate, how uncertain the estimate is, and whether a difference matters in use.

Finally, the safety counts demonstrate the importance of interpreting denominators carefully. Ocular groups list 72 at risk, while nonocular/systemic groups list 36, and the record does not clarify the unit behind each count. A clear account of whether a denominator represents participants, eyes, or observations is necessary for meaningful comparisons. In this respect, the registry offers useful summary results while leaving several analysis details unreported.

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 central limitation is the lack of a reported statistical analysis plan. Although the study is randomized and crossover, the registry does not describe the model used for the outcome comparison or whether it accounted for sequence, period, paired measurements, or correlation between eyes from the same participant. This matters because the endpoint was collected separately for each eye, while the displayed count is 36 for each product and the exact analysis unit is not clarified.

The registry states that no formal hypothesis testing was planned and does not report a clinically meaningful difference threshold. The unadjusted p-value and confidence interval can describe the displayed comparison, but the record does not establish that the comparison was a prespecified confirmatory analysis. It also cannot support an equivalence conclusion because no equivalence objective or margin is reported.

The record does not report a washout period, missing-data method, participant flow for the endpoint, or details of how incomplete product periods were handled. It does not provide separate results by randomized sequence or information on possible period effects. The masking description is limited to single masking, without identifying who was masked or how masking was maintained. These omissions restrict assessment of bias and reproducibility.

The endpoint concerns distance VA at the stated Day 30 assessment after a minimum of 6 hours of wear for each product. The registry does not report a threshold for clinical importance or additional information that would broaden interpretation beyond that measure and timeframe. Safety entries report zero events in the listed categories, but further event-collection and attribution details are not reported in the registry record.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Clinical Performance Assessment of a Daily Wear Monthly Replacement Soft Silicone Hydrogel Contact Lens — NCT04055519.
• Registry record last updated 2021-05-13; status last verified 2021-04.
• Results first posted 2021-05-13.
• 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

NCT04055519 is a completed randomized, single-masked crossover study sponsored by Alcon Research. It enrolled 36 participants and assessed lehfilcon A contact lenses (LID017569) and comfilcon A contact lenses (Biofinity) in randomized wearing sequences. The stated regimen was daily wear in both eyes for 30 days per product, at least 8 hours a day and 5 days a week, with nightly removal for cleaning and disinfection.

The primary endpoint was distance VA in logMAR at Day 30 after a minimum of 6 hours of wear for each product. The registry reports means of -0.13 for LID017569 and -0.14 for Biofinity, with standard deviations of 0.06 for each. The unadjusted mean difference is -0.01, with a confidence interval from -0.038 to 0.018 and an unadjusted p-value of 0.48. The registry states that no formal hypothesis testing was planned.

Serious and other adverse-event counts were zero in the listed groups, as were deaths. The record does not report a detailed crossover analysis method, missing-data approach, or clinically meaningful difference threshold.