Comparison of Clinical Performance of Two Monthly Replacement Toric Soft Contact Lenses: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Clinical Performance of Two Monthly Replacement Toric Soft Contact Lenses (NCT06165627), a randomized na study. The primary outcome is Mean Distance Visual Acuity With Study Lenses at Day 30.

2. Clinical Question

The statistical question is about the difference in average measured visual acuity, not about whether either lens is suitable for an individual. The reported endpoint is assessed for each eye individually while the study lens is in place. The record presents a mean for T30fA and a mean for Biofinity Toric, alongside a mean difference and an interval for that difference. It does not provide separate results by randomized sequence or a description of how the crossover structure was incorporated into the comparison.

3. Trial Design

The study is listed as randomized, double-masked, and crossover, with an enrollment of 67. It is marked completed. Its recorded start date is 2024-01-23, and its primary completion date is 2024-05-12. The registry lists the phase as not applicable.

In a crossover design, participants receive more than one study treatment in successive periods. In this trial, the two described sequences reverse the order of the toric lenses: T30fA followed by Biofinity Toric, or Biofinity Toric followed by T30fA. Randomization assigns the sequence. This design can allow comparisons within the same participant, but the registry record does not state whether the posted comparison uses paired observations, how period or sequence effects were handled, or whether any washout was used. Those details are not reported in the registry record and should not be inferred from the design label alone.

The arm descriptions say that lenses were worn in both eyes during waking hours for at least 12 hours per day. Each wear period is described as 30 days [-1/+3 days] according to the randomization assignment. The primary outcome was assessed at Day 30 of each wear period. The record lists lehfilcon A and comfilcon A toric contact lenses as devices and also lists CLEAR CARE. The described randomized sequences and the reported primary comparison concern T30fA and Biofinity Toric.

The planned enrollment is not separately described from the recorded enrollment. The trial's original sample-size justification, anticipated treatment difference, original power target, and any interim analyses are not reported in the registry record. The record lists one outcome measure and no posted analyses apart from the presented outcome values and comparison. It does not give a fuller statistical analysis plan.

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: Of the 67 enrolled, 1 participant was discontinued following randomization but prior to exposure to the study lenses. This reporting group includes all participants exposed to any study lenses evaluated in this study (66).

First Wear Period (Approx. 30 Days)

Second Wear Period (Approx. 30 Days)

Analysis population for the primary outcome, as defined in the registry: Safety Analysis Set: All subjects/eyes exposed to any study lenses evaluated in this study with non-missing response. Note, One subject in the Biofinity Toric arm lost a lens on the way to the visit. Hence, the assessment was taken on 1 eye only.

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 Mean Distance Visual Acuity With Study Lenses at Day 30, measured over Day 30 of each wear period. A wear period was 30 days [-1/+3 days] according to randomization assignment..

The primary endpoint is mean distance visual acuity with study lenses at Day 30 of each wear period. Visual acuity was measured eye by eye with the lens in place while the participant read letter charts. Results are expressed in logarithm minimum angle of resolution, or logMAR. The registry explains that a logMAR value of 0 corresponds to 20/20 Snellen visual acuity and that lower logMAR values represent better eyesight.

Visual acuity is a continuous measurement, so the reported outcome is a mean with a standard deviation rather than a count of people meeting a threshold. Comparing means describes the average measured value in each lens group. The mean difference provides a summary of the numerical separation between those averages. The registry reports T30fA at -0.07 logMAR and Biofinity Toric at -0.06 logMAR. These are close values on the reported scale; their clinical importance cannot be determined from the means alone because a threshold for a meaningful difference is not reported in the registry record.

The registry defines the outcome population as the Safety Analysis Set: all subjects or eyes exposed to any study lenses and evaluated with a non-missing response. It notes that one subject in the Biofinity Toric arm lost a lens on the way to the visit, so the assessment was taken on one eye only. This detail matters because visual acuity is measured at the eye level, while the study sequence is assigned to participants. The record does not fully explain the handling of two eyes from the same participant in the analysis.

7. Results Posted in the Registry

• Biofinity Toric: mean -0.06 versus -0.07 on control; difference 0.01 (95% CI -0.01 to 0.03), standardized effect d = 0.17; z-test p = 0.348.

8. Statistical Interpretation

9. Statistical Methods Explained

The outcome is continuous: each eye receives a logMAR visual-acuity measurement, and the registry reports the mean and standard deviation for each lens. A mean describes the central average of the recorded measurements. A standard deviation describes how spread out measurements are around that average. These quantities answer different questions: the mean gives a summary of the typical level, while the standard deviation describes variation among measurements. Neither alone shows the full distribution of results.

What does the mean difference represent?

The posted comparison gives a mean difference of 0.01 logMAR for Biofinity Toric relative to T30fA. Its direction follows the ordering of the reported means: Biofinity Toric is -0.06 and T30fA is -0.07. Because lower logMAR is better on this scale, the positive difference means the Biofinity Toric mean is numerically higher, or less low, than the T30fA mean. This is a group-average contrast, not a description of the difference for every eye or participant.

The comparison also reports the group standard deviation as 0.06 for each lens. Similar reported spreads do not imply that individual responses were identical or that measurements from the same participant were independent. In general, a crossover study may produce paired observations, and paired analysis can use the association between a participant's measurements. The analysis method used for the posted estimate is not reported in the registry record. It is therefore not possible to tell from the record whether the estimate reflects a paired, crossover-specific analysis or a simpler comparison of group summaries.

How should the p-value be read?

The unadjusted p-value is 0.348. In general, a p-value describes how compatible the observed data are with a specified null hypothesis under the assumptions of the statistical test. It is not the probability that the null hypothesis is true, and it does not measure the size or practical importance of a difference. A p-value that is not small does not prove that the two means are the same. Here, it accompanies an estimate close to zero and an interval that crosses zero, so the results leave uncertainty about the direction and size of the difference.

The record calls the p-value unadjusted. No adjustment for multiple testing is described. There is one posted outcome measure and zero secondary outcomes posted, but the registry does not explain whether other outcomes or analyses were planned, conducted, or considered in the study's analysis plan. The p-value should not be treated as if multiplicity has been addressed.

Why does design matter for the analysis?

In general, crossover data can contain measurements from the same participant under each treatment. Such measurements may be correlated. Treating correlated measurements as if they came from unrelated participants can misrepresent the uncertainty. Period effects, sequence effects, and changes over time may also be relevant in crossover studies. The registry identifies the study as crossover and gives the two randomized orders, but it does not describe how these considerations were handled. It also does not report a washout period or a model specification. These methodological details are not reported in the registry record.

There is also an eye-level consideration. The outcome is measured for each eye, and the record defines the analysis set using subjects or eyes. Measurements from two eyes in the same participant may be related. The record does not state how that relationship was handled, nor does it give the number of participants contributing paired eye-level observations to each posted result. It notes that one subject in the Biofinity Toric arm had only one eye assessed after losing a lens on the way to the visit.

What can the reported quantities establish?

The mean, standard deviation, mean difference, interval, and p-value describe the posted continuous outcome comparison. They do not reveal the distribution of individual changes, the proportion of participants who improved, or the performance of each lens for every participant. Those results are not reported in the registry record. The comparison is also not an equivalence or non-inferiority analysis on the information available: no margin or decision rule for either purpose is reported.

In general, statistical significance and clinical importance are distinct. A small p-value would not by itself show that a difference matters to patients, and a larger p-value does not show that the treatments are equivalent. Judging importance requires context, including a threshold or interpretation framework for the scale, neither of which is reported in the registry record. The posted data support describing the observed means and their uncertainty, without converting the result into a claim of benefit or lack of benefit.

10. Confidence Intervals and Precision

The reported mean difference is 0.01 logMAR, with an interval extending from a small negative value to a small positive value. The registry does not state the confidence level for that interval, so its level is not reported in the registry record. Because the interval crosses zero, the data are compatible with a small difference in either direction under the interval procedure used. The interval does not establish that the means are exactly equal.

Precision concerns the range of values that remain compatible with the data and the analysis, not whether the point estimate looks close to zero. The posted interval spans both sides of zero, so it does not settle the direction of the difference. Its endpoints are close to zero on the logMAR scale, but the registry does not provide a threshold for a clinically meaningful difference. Statistical uncertainty and practical importance therefore cannot be collapsed into a single conclusion.

The p-value of 0.348 is consistent with uncertainty around a small estimated difference, but it is not a substitute for the interval. The standard deviations are 0.06 for both groups. The reported comparison also gives standard errors, but the registry does not describe the method used to derive them or clarify how the crossover and eye-level structure were incorporated. That omission limits independent appraisal of the interval's precision.

The endpoint results include 65 for T30fA and 62 for Biofinity Toric. The registry defines the analysis set as exposed subjects or eyes with a non-missing response, but does not fully clarify whether the reported counts represent participants, eyes, or another analysis unit. It notes one one-eye assessment in the Biofinity Toric arm. This matters because the outcome is measured for each eye and observations may be related within participants. No confidence level or fuller analysis description is 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 sample-size figures are planning illustrations based on the observed effect, not a report of the trial's original design calculation. They are expressed as participants per arm, not as total events. The assumptions listed for the illustration are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is set at the stated fraction of the observed effect.

The 80% power column gives the illustrative number of participants per arm for a design that would have an 80% chance of detecting the specified effect if the assumptions and effect were correct. The 90% power column describes the corresponding planning target for a 90% chance. These are prospective planning concepts; they do not describe the probability that the completed trial's result is true. This illustration is not observed power.

The rows consider planning for 100%, 75%, and 50% of the observed effect. For the full observed effect, the illustration lists 566 participants per arm for 80% power and 757 participants per arm for 90% power. For 75% of the observed effect, it lists 1,005 per arm and 1,345 per arm, respectively. For 50% of the observed effect, the corresponding figures are 2,261 and 3,027 per arm. Smaller effects need more participants to detect under the same planning assumptions.

These figures should not be read as the number enrolled, analyzed, or needed to validate the trial's conclusion. They are based on the observed difference and a simplified two-arm calculation. The study itself is a crossover trial, while the illustration assumes equal allocation between two arms and does not describe a crossover-specific calculation. The trial's own sample-size assumptions and justification 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 = 0.060.
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(6165627)
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: 0.801 (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 posted. It lists zero analyses, so detailed analysis outputs or model descriptions are not reported. The posted comparison includes an unadjusted p-value, but the registry does not say whether any multiplicity strategy was planned or used. The number of outcomes in the registry alone cannot establish how many analyses were conducted or considered.

Multiplicity arises when several hypotheses are tested: the more tests performed, the greater the chance of at least one apparently unusual result under a set of null hypotheses. In general, adjustment or a prespecified hierarchy can address this issue. Whether either approach was applicable or used in this trial is not reported in the registry record. The unadjusted p-value should therefore be interpreted as the reported single comparison, without assuming correction for additional testing.

The analysis population is described as the Safety Analysis Set, comprising subjects or eyes exposed to any study lenses and evaluated with a non-missing response. Results list 65 for T30fA and 62 for Biofinity Toric. The registry does not explain in detail how missing outcome values were handled, whether any imputation was used, or how the analysis set maps to participants versus eyes. It specifically notes that one subject in the Biofinity Toric arm lost a lens on the way to the visit and had an assessment on one eye only.

For a crossover trial, missing one period or one eye can affect the available comparisons differently, depending on the analysis method. The record does not state whether participants with incomplete measurements contributed to a paired analysis, how incomplete sequences were handled, or whether any sensitivity analyses were conducted. The treatment of missing data and the analysis populations beyond the stated Safety Analysis Set are not reported in the registry record. These gaps limit assessment of whether the posted estimate could be affected by missing measurements or analysis choices.

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 and other adverse events separately for pretreatment, T30fA ocular, T30fA nonocular, Biofinity Toric ocular, and Biofinity Toric nonocular categories. Each listed category has zero affected entries for serious events and zero affected entries for other events. Deaths are also listed as zero in each category, and no serious event terms are listed.

The record gives the number at risk for each category: 66 for pretreatment, 132 for each ocular treatment category, and 66 for each nonocular treatment category. These are the registry's category-specific denominators, not a count to combine across rows. In particular, the ocular categories may represent eyes, and the registry does not explain the denominator structure further in this adverse-event listing.

Zero recorded events means none were entered for those categories in the posted record. It does not show that the possibility of an event is absent, and it does not resolve the visual-acuity comparison. The adverse-event timeframe and further details about collection or attribution are not reported in the registry record.

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

The posted results describe mean distance visual acuity at Day 30 of each wear period. T30fA had a mean of -0.07 logMAR and Biofinity Toric had a mean of -0.06 logMAR. The difference reported for Biofinity Toric relative to T30fA is 0.01 logMAR. Since lower values correspond to better eyesight, the T30fA mean is numerically lower. The reported interval crosses zero, and the unadjusted p-value is 0.348, leaving uncertainty about the direction and size of any underlying difference.

These results do not establish that the lenses are equivalent. Equivalence requires a prespecified margin and an analysis designed to assess whether the difference lies within that margin; neither is reported in the registry record. Nor do the results establish non-inferiority or a clinically important advantage. The registry does not report a threshold for interpreting the size of a difference on the logMAR scale.

The finding concerns group averages for a measured visual-acuity endpoint, not every participant's experience. The record does not provide distributions of individual changes, responder counts, or results by randomized sequence. The crossover design means each sequence received both study lenses, but details of the analysis of repeated observations and eyes are not reported. This limits how fully the posted comparison can be interpreted as accounting for the design.

The safety listing records zero serious events, zero other events, and zero deaths in its categories. These are descriptive entries from the registry and should not be generalized beyond the reported record. Taken together, the posted data support a narrow statistical description: the two reported average values are close, and the uncertainty interval does not identify a clear direction. They do not support a broader claim that one lens works better, that the lenses perform the same, or that there is no risk.

16. Why This Trial Matters Statistically

This trial is statistically notable because it combines a crossover design with an outcome measured separately for each eye. Crossover designs can make within-participant comparisons informative, but valid uncertainty estimates depend on how repeated measurements, periods, and treatment sequence are handled. Eye-level measurements can also be correlated within a participant. The registry identifies the design and measurement level, yet does not report the analytical details needed to evaluate these dependencies.

The observed mean difference is small relative to the scale values reported, and its interval includes zero. That makes precision and interpretation more important than a simple focus on whether a p-value crosses a threshold. The unadjusted p-value is 0.348, but it does not establish equality or explain whether a difference would matter. A clinically meaningful threshold is not reported in the registry record.

The planning illustration also shows how strongly sample-size requirements depend on the effect being targeted: planning for a smaller fraction of the observed effect requires more participants per arm under the listed assumptions. These are generic planning illustrations rather than the original design rationale, and their two-arm assumptions do not describe the crossover analysis in detail.

Finally, the result illustrates a common limitation of registry reporting: numeric outcome summaries may be available while key details about analysis populations, missing data, multiplicity, and crossover modeling are not. A careful reading separates what is directly reported—the means, difference, interval, and p-value—from what would require a fuller analysis plan or report.

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 leaves important analytical details unspecified. It identifies a randomized, double-masked crossover design and gives the two treatment orders, but does not report the model used for the primary comparison or whether it accounted for participant-level pairing, period, sequence, or possible carryover effects. No washout information is reported. These omissions prevent a detailed assessment of how closely the estimate reflects the crossover structure.

The outcome is measured for each eye, while the treatment sequence is assigned to participants. The record does not explain how correlations between two eyes from the same participant were handled. It also defines the population in terms of subjects or eyes, leaving the precise unit represented by the reported arm counts unclear. One subject in the Biofinity Toric arm had only one eye assessed after losing a lens while travelling to the visit.

Missing-data procedures, sensitivity analyses, and analysis populations beyond the stated Safety Analysis Set are not reported in the registry record. The record lists one outcome measure, no secondary outcomes, and zero analyses, but does not describe whether other outcomes or tests were planned or performed. The confidence level for the interval and the original statistical analysis plan are also not reported.

Finally, no clinically meaningful difference threshold, equivalence margin, or non-inferiority margin is reported. The posted summary statistics therefore support description of the observed means and their uncertainty, but not a definitive judgment about clinical importance or equivalence.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Comparison of Clinical Performance of Two Monthly Replacement Toric Soft Contact Lenses — NCT06165627.
• Registry record last updated 2025-05-29; status last verified 2025-05.
• Results first posted 2025-05-29.
• 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

NCT06165627 is a completed randomized, double-masked crossover study comparing T30fA, identified as lehfilcon A toric contact lenses, with Biofinity Toric, identified as comfilcon A toric contact lenses. The registry lists an enrollment of 67 and conditions of ametropia and astigmatism. Participants were assigned to opposite sequences of the two lenses.

The primary outcome is mean distance visual acuity in logMAR at Day 30 of each wear period. The posted means are -0.07 for T30fA and -0.06 for Biofinity Toric; the reported mean difference is 0.01, with an interval crossing zero and an unadjusted p-value of 0.348. Lower logMAR values represent better eyesight.

The record lists zero serious and other adverse events and zero deaths in its reported categories. Further details of the crossover analysis, missing-data handling, and the trial's original sample-size rationale are not reported in the registry record.