Clinical Performance of Two Reusable Silicone Hydrogel Contact Lenses: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Clinical Performance of Two Reusable Silicone Hydrogel Contact Lenses (NCT05431478), a randomized na study. The primary outcome is Visual Acuity With Study Lenses at Week 1 Follow-Up.

2. Clinical Question

3. Trial Design

This was a randomized, double-masked, crossover study of serafilcon A (LID022821) and senofilcon A (AOHP) contact lenses. The registry record lists an enrollment of 68 and a completed study. The recorded start date is 2022-07-15 and the primary completion date is 2022-09-09. The study has no applicable phase designation.

In a crossover design, participants receive each intervention in sequence rather than remaining in one treatment group throughout. The two randomized sequences were LID022821 followed by AOHP, or AOHP followed by LID022821. Each lens type was worn bilaterally for at least 10 hours per day for approximately 14 days. Visual acuity was assessed at Week 1 in each wear period. The registry description does not give further details about the timing of assessments or any transition between periods.

The crossover structure matters for interpreting the results. The two lens-specific groups of 68 are not evidence of 136 distinct participants: the registry enrollment is 68, and the listed sequences indicate that participants wore both lens types. Measurements under the two lenses are therefore connected through participants, rather than representing two wholly separate groups. Paired or otherwise crossover-aware methods can use that connection, but the registry record does not report the statistical model used for the posted comparison.

The intervention list also includes CLEAR CARE, described as the daily cleaning and disinfection product. The stated clinical purpose was to assess the performance of the two reusable silicone hydrogel contact lenses during daily wear. The sponsor was Alcon Research. Further protocol details, including original design assumptions and any washout procedures, are not reported in the registry record.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Before assignment: This reporting group includes all enrolled participants/eyes (68/136).

Period 1, Approximately 14 Days

Period 2, Approximately 14 Days

Analysis population for the primary outcome, as defined in the registry: Safety Analysis Set.

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: Safety Analysis Set: All subjects/eyes exposed to any study lenses evaluated in this study.

6. Primary Endpoint

The registry lists the primary outcome as Visual Acuity With Study Lenses at Week 1 Follow-Up, measured over Week 1, each wear period. A wear period was approximately 14 days..

The primary endpoint is visual acuity with the study lens in place at Week 1 of each wear period. The registry describes measurement using logarithmic Minimum Angle of Resolution charts and reports the result as a mean in logMAR, with standard deviation as the dispersion measure. Each eye was assessed individually, and the analysis population is identified as the Safety Analysis Set.

Visual acuity is relevant to this study because the stated aim is to assess clinical performance of the lenses while they are being worn. The logMAR scale expresses acuity numerically: the registry notes that 0.0 corresponds to 20/20 Snellen acuity, and a negative value denotes better than 20/20 visual acuity. The posted mean values are negative for both lenses. These group means describe the average recorded acuity; they do not show the range of individual results or whether every participant had the same result.

The registry explicitly states that no hypothesis testing was pre-specified for this endpoint. That distinction is important: a reported mean and its dispersion are descriptive summaries, while a hypothesis test addresses a specified inferential question. A recalculated comparison can help describe the difference and its uncertainty, but it does not change the stated endpoint or establish that a formal hypothesis test was part of the original plan. Additional details about the clinical threshold for a meaningful difference are not reported in the registry record.

7. Results Posted in the Registry

• AOHP: mean -0.11 versus -0.12 on control; difference 0.01 (95% CI -0.02 to 0.04), standardized effect d = 0.13; z-test p = 0.438.

8. Statistical Interpretation

9. Statistical Methods Explained

What does a mean describe?

A mean is the arithmetic average of the observations included in a group summary. Here, it gives a compact description of visual acuity with each study lens in place at Week 1 of the relevant wear period. The LID022821 mean is -0.12 logMAR, and the AOHP mean is -0.11 logMAR. A mean alone does not indicate how tightly individual observations cluster around that average, whether the distribution is skewed, or whether some participants had results far from it.

The reported standard deviation describes spread among observations around the group mean. The standard deviations are 0.07 for LID022821 and 0.08 for AOHP. Standard deviation is not the same as the standard error: the former describes variation among observations, while the latter describes the uncertainty in an estimated mean. The registry record does not explain how eye-level measurements were combined or modeled in the reported summaries, even though each eye was assessed individually.

What does the mean difference represent?

The recalculated unadjusted mean difference is expressed as AOHP minus LID022821, yielding 0.01 logMAR. Its sign indicates the direction of that subtraction, not a judgment about clinical importance. This is a simple comparison of the posted group means. It is not, by itself, evidence that the original analysis used the same calculation or that it incorporated the crossover structure.

Because each participant wore both lenses, an analysis could account for paired observations. In paired data, the difference within a participant can be more informative than treating observations under each lens as unrelated. The uncertainty of that difference depends on how the measurements move together within participants. The registry record does not report a paired analysis, a mixed model, a period effect, a sequence effect, or another crossover-specific method. Those details should not be inferred from the displayed means and standard deviations.

How should the confidence interval be understood?

A confidence interval expresses uncertainty around an estimated effect under the assumptions of its calculation. It gives a range of values that are reasonably compatible with the observed estimate and method; it is not a range containing a fixed proportion of individual participants’ measurements. The recalculated interval for the mean difference extends below and above zero. That means the calculation does not pin down the direction of the difference with high precision. The interval is an unadjusted recalculation from summary statistics and should not be taken as a substitute for a reported crossover-model interval.

Precision depends on both the amount of information and the variability relevant to the estimate. A narrow interval gives a more precise estimate than a wide interval, while an interval spanning meaningfully different effects leaves more uncertainty. Whether the interval rules out clinically important effects cannot be assessed from the registry record because it does not state a clinical equivalence margin or other threshold for importance.

What does the p-value add?

The recalculated unadjusted p-value is 0.438. In general, a p-value is a measure of how unusual results at least as incompatible with a specified null hypothesis would be if that hypothesis and the calculation assumptions were true. It is not the probability that the null hypothesis is true, and it is not a measure of the size or importance of an effect. The registry explicitly states that no hypothesis testing was pre-specified for this endpoint. The recalculated p-value therefore describes an unadjusted calculation, not a pre-specified confirmatory analysis.

The p-value and confidence interval are related ways of describing uncertainty for a particular calculation, but neither removes concerns about whether the calculation matches the study design. In a crossover trial, treating repeated observations as independent can misrepresent uncertainty. Since the registry does not report the statistical model, the recalculated p-value should be interpreted cautiously and not as a definitive assessment of the paired trial data.

Why does variation matter?

Variation affects how much information the results provide about a mean or contrast. The standard deviations describe observed dispersion, but they do not reveal the full correlation structure across eyes, participants, periods, and lens conditions. In studies with correlated observations, an analysis must account for that dependence to estimate uncertainty appropriately. General statistical practice recognizes that ignoring dependence can make standard errors and confidence intervals misleading; the direction and extent of any difference cannot be determined from this record.

The registry does not report a missing-data method, an imputation procedure, or how incomplete period or eye measurements would be handled. It also does not report an analysis model, covariate adjustment, or sensitivity analysis. These absences limit what can be reconstructed from the posted aggregate summaries. The trial’s original statistical plan and design assumptions are not reported in the registry record.

What is and is not established by recalculation?

A recalculated result uses the posted summary statistics to provide a simple unadjusted comparison. It is useful for orienting readers to the magnitude and direction of the difference and its approximate uncertainty. It does not recover participant-level data, adjust for the crossover sequence, or verify how the sponsor analyzed the trial. The discrepancy field is false, so there is no posted discrepancy flag indicating a conflict that would require the sponsor’s own analysis to take precedence. Even so, the registry record does not contain a sponsor-reported inferential analysis for this endpoint.

For this reason, the most defensible statistical reading combines the descriptive lens-specific means with the limitations of the recalculation. The means are reported outcomes; the comparison is unadjusted; the design is crossover; and the record does not describe a model that connects those elements. This distinction preserves the useful descriptive information without assigning more certainty to the comparison than the record supports.

10. Confidence Intervals and Precision

The posted standard deviations are 0.07 for LID022821 and 0.08 for AOHP. They describe the spread of the recorded visual acuity values around each lens-specific mean. They are not confidence limits, and they do not by themselves show how precisely the mean difference is estimated.

The recalculated unadjusted mean difference is 0.01 logMAR, with a confidence interval that extends on both sides of zero. The interval therefore leaves uncertainty about the direction of the difference under the unadjusted calculation. It should not be read as proof that there is no difference: values on either side of zero remain compatible with that interval. Nor does it establish equivalence, because the registry record does not state an equivalence margin or a clinical threshold for an important difference.

Precision is also tied to the study design and analysis. Participants wore both lens types, so a crossover-aware estimate could make use of the paired measurements. The registry record does not describe whether the posted comparison accounts for that pairing. The interval is therefore best treated as an unadjusted recalculation from posted summary statistics, not as a definitive measure of uncertainty from a fully specified crossover analysis.

The endpoint measures acuity at Week 1 of each wear period, and the sample summaries do not reveal the distribution of individual values or any results at other times. The interval’s statistical precision cannot answer whether the measured difference matters clinically. That interpretation would require a meaningful threshold, which is 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 figures are participants per arm, not total events. They are illustrations computed from the observed effect, rather than the trial’s original design assumptions. The listed assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning scenario asks how many participants per arm would be needed to detect a stated fraction of the observed effect.

For planning for 100% of the observed effect, the listed values are 887 participants per arm for 80% power and 1,188 participants per arm for 90% power. For planning for 75% of the observed effect, the corresponding values are 1,577 and 2,111 participants per arm. For planning for 50% of the observed effect, they are 3,548 and 4,750 participants per arm.

In plain language, 80% power is the assumed chance of detecting the specified effect under the planning assumptions if that effect is present; the 90% column uses a higher target chance of detection. These are planning illustrations, not observed power. Smaller effects are harder to detect and therefore require more participants under the same assumptions. The values do not establish what enrollment the trial needed under its actual design, and they do not incorporate a reported crossover-specific calculation. The trial’s own original sample-size justification and design assumptions are not reported in the registry record.

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 = 0.075.
2. n = 2 × (1.96 + 0.842)² × 0.075² / 0.010² = 886.9, rounded up to 887 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 <- 0.0751664818918645                     # 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(5431478)
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 = 887 (80% power), 1,188 (90% power)
 75% of observed effect: n per arm = 1,577 (80% power), 2,111 (90% power)
 50% of observed effect: n per arm = 3,548 (80% power), 4,750 (90% power)
power.t.test: 887.9 
Simulated power at n = 887 per arm: 0.803 (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 outcome measure and no secondary outcomes. It states that no hypothesis testing was pre-specified for the primary endpoint. The unadjusted p-value associated with the recalculated comparison should therefore not be interpreted as the outcome of a stated pre-specified testing plan. No multiplicity adjustment is reported, and the registry record does not describe a family of confirmatory tests or a hierarchy of endpoints.

Multiplicity becomes relevant when several outcomes, comparisons, time points, or subgroups are tested. In general, conducting many tests can increase the chance of obtaining an apparently unusual result by chance. The record does not report such a testing program, but it also does not give a complete statistical analysis plan from which all planned comparisons could be checked. Whether any additional analyses were conducted outside the posted record is not reported in the registry record.

The analysis population is identified as the Safety Analysis Set. The registry record does not further define membership in that set or state how participants with incomplete measurements were handled. A missing-data procedure, such as complete-case analysis or imputation, is not reported. It is also not reported whether all enrolled participants contributed data to each lens-specific mean or whether both eyes and both periods were available for everyone.

The crossover design raises specific analysis questions, including how within-participant pairing and period or sequence effects were handled. Those methods are not reported in the registry record. There are no posted analysis rows. Consequently, the available summaries do not establish whether the inferential comparison used a model appropriate to the crossover design, how missing data were incorporated, or whether the analysis population was restricted in a way that affected the estimate.

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 registry lists serious adverse events as affecting 0 participants in each reported group, and deaths as 0 in each group. For pretreatment, the reported at-risk counts were 68, with 0 serious adverse events and 0 other adverse events affected. For each lens-specific ocular group, the at-risk count was 136; serious adverse events and other adverse events affected 0. For each lens-specific non-ocular group, the at-risk count was 68, with 0 serious adverse events and 0 other adverse events affected.

These are the event counts recorded in the registry for the stated groups and at-risk denominators. They do not establish that no unrecorded events occurred, and they should not be generalized beyond the participants and periods represented by the record. The registry’s group labels distinguish ocular and non-ocular categories for each lens, but the record does not provide further detail about the at-risk counting method. No top serious-event terms are listed. These safety figures are descriptive registry reports, not a statistical comparison of safety between lenses.

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

The posted results describe mean visual acuity at Week 1 of each wear period for two reusable silicone hydrogel contact lenses. The mean was -0.12 logMAR with LID022821 and -0.11 logMAR with AOHP. The recalculated unadjusted difference was 0.01 logMAR, and its confidence interval extended to both sides of zero. The record therefore presents close group means but leaves uncertainty around the direction and size of the contrast.

That description does not establish that the lenses are equivalent, interchangeable, or different in a clinically important way. Equivalence requires a prespecified margin and an analysis designed to assess whether the uncertainty lies within that margin; neither is reported in the registry record. The record also states that no hypothesis testing was pre-specified for the endpoint. The unadjusted recalculation should not be treated as a substitute for such a plan.

Interpretation is further limited by the crossover design and the absence of reported crossover-analysis details. The participants wore both lenses in randomized sequence, but the record does not state how the paired measurements, periods, or sequence were handled in an inferential model. The posted summary statistics cannot resolve those questions. The outcome is also limited to visual acuity at the stated follow-up time; it does not by itself summarize every aspect of lens performance or later experience.

The registry reports zero affected participants for serious and other adverse events in the listed groups, and zero deaths. These are the reported counts for the recorded groups, not proof of absence of any unreported event or a comparative safety conclusion. Overall, the record supports a descriptive account of the endpoint and safety counts, while leaving important details about clinical thresholds, missing data, and analysis methods unreported.

16. Why This Trial Matters Statistically

This trial illustrates why the design and the statistical summary need to be read together. A randomized crossover study lets participants wear both lens types, so each participant can contribute observations under both conditions. That structure can make within-participant comparisons informative, but it also means that the two lens-specific sets of observations are not automatically independent. The method used to account for pairing is important to the uncertainty around a contrast.

The registry provides means and standard deviations for each lens, along with a recalculated unadjusted comparison, but does not report a crossover-specific model or a prespecified hypothesis test. That contrast between descriptive results and inferential claims is a central statistical lesson: arithmetic comparisons can be useful, but their uncertainty depends on the study design and assumptions behind the calculation. A reader should distinguish the reported outcomes from any additional recalculation.

The record also shows why a small numerical difference and an imprecise interval should not be converted into a claim of equivalence. Such a conclusion needs a clinical threshold and a suitable analysis, neither of which is reported. Likewise, sample-size planning figures based on the observed effect are illustrations, not evidence about the trial’s original design or its observed power. Clear reporting of the intended analysis, missing-data approach, and clinically meaningful thresholds would make the inferential context easier to evaluate.

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 primary result is a mean visual acuity measurement at Week 1 of each wear period. The registry does not report additional primary time points, secondary outcome measures, or a clinical threshold for interpreting the difference. It also does not provide individual participant results or enough distributional detail to assess the shape of the outcome data from the group summaries.

The study is a crossover trial, but the record does not describe a crossover-aware statistical model or report how within-participant correlation, period, or sequence was handled. No hypothesis testing was pre-specified for the endpoint, and no analysis rows are posted. The recalculated unadjusted comparison consequently cannot answer whether a model-based analysis would yield different uncertainty.

The registry identifies the Safety Analysis Set but does not define it in detail. Methods for missing measurements, incomplete periods, or eye-level data are not reported. The original sample-size justification and the trial’s design assumptions are also not reported in the registry record. Planning illustrations based on the observed effect should not be used to infer the study’s original enrollment rationale.

The record reports zero serious adverse events and zero deaths in the listed groups, but does not provide event narratives or further details about the at-risk counting method. The results are therefore limited to the specific outcome and safety summaries posted in the registry. They should not be extended to unreported outcomes or interpreted as establishing clinical equivalence or a comprehensive safety comparison.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Clinical Performance of Two Reusable Silicone Hydrogel Contact Lenses — NCT05431478.
• Registry record last updated 2023-09-21; status last verified 2022-09.
• Results first posted 2023-09-21.
• 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

NCT05431478 is a completed, randomized, double-masked crossover study sponsored by Alcon Research. It enrolled 68 participants with refractive errors and compared serafilcon A lenses (LID022821) with senofilcon A lenses (AOHP). Participants were randomized to wear the lens types in opposite sequences. Each lens was worn bilaterally for at least 10 hours per day for approximately 14 days, with CLEAR CARE used for daily cleaning and disinfection.

The primary outcome was mean visual acuity with study lenses at Week 1 of each wear period, measured in logMAR. The posted means were -0.12 for LID022821 and -0.11 for AOHP. The recalculated unadjusted mean difference was 0.01 logMAR, with an interval extending on both sides of zero and an unadjusted p-value of 0.438. No hypothesis testing was pre-specified for this endpoint. The registry reports zero serious adverse events and zero deaths in the listed groups. Crossover analysis details, missing-data methods, and the original sample-size justification are not reported in the registry record.