A Study to Evaluate the Product Feasibility of a New Silicone Hydrogel Contact Lens: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Study to Evaluate the Product Feasibility of a New Silicone Hydrogel Contact Lens (NCT01412983), a randomized na study. The primary outcome is Visual Acuity.

2. Clinical Question

3. Trial Design

The registry describes a completed, randomized, single-masked crossover study sponsored by Bausch & Lomb Incorporated. It lists the condition as myopia and enrollment as 100. The recorded start was 2011-08, and primary completion was 2011-09. The study was not assigned a phase; the phase entry is NA. Its stated objective was to determine clinical feasibility and evaluate the performance of investigational lenses developed by Bausch + Lomb.

The two devices were the Bausch + Lomb investigational soft contact lens and the Ciba Vision Air Optix Aqua soft contact lens. In general, a crossover design compares interventions across periods within participants, but the registry does not report the allocation sequence, period schedule, lens-wearing duration beyond the one-week outcome timeframe, or any washout arrangements. It also does not explain how the single masking was implemented or who was masked. Those details should not be inferred from the design labels alone.

The primary outcome was visual acuity, measured in LogMAR, at one week. Its stated population was all eligible dispensed eyes. The arm summaries report 96 eyes for the test lens and 95 for the comparator. Overall comfort was the posted secondary outcome, also at one week; its arm counts were 96 and 97. These outcome counts are not necessarily counts of distinct participants, and the registry does not explain the differences among them. The enrollment figure and outcome-specific counts describe different record entries and should not be treated as interchangeable.

The registry lists two outcome measures and no reported analyses. It does not report the original statistical analysis plan, the original sample-size justification, missing-data procedures, or whether analyses accounted for the crossover structure. The registry record marks the study as completed. Its posted results therefore describe particular outcome summaries, while several details needed to assess how those summaries were generated 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: 100 participants (200 eyes) were enrolled in this 2 week crossover study. Participants were divided into 2 groups wearing one study lens for 1 week and then crossing over to the other study lens for 1 week. 96 participants completed the study, 1 participant was ineligible at baseline while 3 participants were discontinued during the study.

1st Period

Reasons for not completing this period:

2nd Period

Analysis population for the primary outcome, as defined in the registry: All eligible dispensed eyes

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: All participants enrolled in the study

6. Primary Endpoint

The registry lists the primary outcome as Visual Acuity, measured over One week.

The primary endpoint is visual acuity measured in LogMAR, with the timeframe recorded as one week. The outcome description specifies the mean difference in high-contrast LogMAR across all lens visual acuities between the lens groups, among all eligible dispensed eyes. A continuous endpoint such as this retains information about the measured values rather than reducing them to a simple count of participants who did or did not meet a threshold. Comparing group means is one way to describe the average difference in the recorded measurement.

The registry labels the arm summaries as least-squares means and gives standard deviations. The posted means are -0.054 for the Bausch + Lomb test lens and -0.051 for the Ciba Vision lens. The comparison is expressed as the Ciba Vision mean minus the test-lens mean, yielding a mean difference of 0.003 LogMAR. These summaries describe the observed outcome values in the posted groups; they do not, by themselves, convey all details of the analysis model or how repeated measurements in a crossover study were handled.

Visual acuity is the primary endpoint because the registry identifies it as the main measure for assessing lens performance. The endpoint provides a quantitative comparison at the stated assessment time. It does not alone capture every aspect of lens experience: overall comfort was recorded separately as a secondary outcome. No clinically important difference threshold for the LogMAR outcome is reported in the registry record, so the endpoint’s numerical scale cannot be used to classify the observed estimate as clinically important or unimportant.

7. Results Posted in the Registry

• Ciba Vision Soft Contact Lens: mean -0.05 versus -0.05 on control; difference 0.00 (95% CI -0.03 to 0.04), standardized effect d = 0.03; z-test p = 0.857.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Overall Comfort

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • Ciba Vision Soft Contact Lens: mean 82.70 versus 81.90 on control; difference 0.80 (95% CI -5.34 to 6.94), standardized effect d = 0.04; z-test p = 0.798.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Ciba Vision Soft Contact Lens and the control. The interval gives the range of effects that remain compatible with the data.

Overall comfort is the one posted secondary outcome. Its group summaries and unadjusted comparison offer an additional view of lens experience alongside the primary visual-acuity endpoint. The secondary estimate is close to zero on its scale, and its confidence interval includes zero. Taken together, the primary and secondary summaries do not point to a clear separation between the lens groups in their reported average outcomes. This is a description of the posted estimates, not proof that the lenses are equivalent on either measure.

Comfort and visual acuity measure different aspects of product performance, so agreement or lack of separation across them does not make one outcome a substitute for the other. The registry identifies visual acuity as primary and comfort as secondary. The primary endpoint therefore has the prespecified priority indicated by the registry’s outcome listing, while the secondary result is best read as supporting context rather than as an independent confirmation of the primary comparison.

Secondary outcomes are often interpreted with less weight because examining multiple outcomes creates more opportunities for apparently notable results to arise by chance. General methods for addressing this include prespecifying a hierarchy or adjusting inference across outcomes. The registry does not report whether either approach was planned or used. The posted comparison is unadjusted, and there are no reported analyses. Consequently, the secondary result should not be used to make a strong inferential claim on its own.

The secondary summary also has its own outcome-specific count and measurement scale. The registry reports 96 observations for the test lens and 97 for the comparator for comfort, while the primary counts differ. It does not describe why the counts differ or how missing measurements were handled. That uncertainty limits assessment of whether the secondary and primary summaries represent precisely comparable sets of participants or eyes. The overall pattern is informative as a record of the outcomes posted, but it does not resolve questions about analysis choices, missingness, or clinical importance.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Overall Comfort

9. Statistical Interpretation

10. Statistical Methods Explained

For a continuous outcome, a mean describes the average recorded value in a group. A standard deviation describes how spread out values are around that average. The registry labels its group estimates as least-squares means and reports standard deviations for both lenses. A least-squares mean is generally a model-based group average, but the registry does not describe the model used to obtain these particular estimates. The posted recalculations use the summary statistics and are unadjusted; they should not be confused with an account of the original model.

What does a mean difference represent?

A mean difference subtracts one group’s average from the other’s. For the primary comparison, the posted estimate is 0.003 LogMAR for Ciba Vision minus Bausch + Lomb. A value near zero describes a small difference between the reported averages on the scale used. The sign depends on the comparison direction: reversing the order of subtraction would reverse the sign without changing the underlying separation between the means. The comparison should therefore be read alongside the stated lens order, not as an isolated signed number.

A mean difference does not describe every individual outcome. Participants or eyes may have values above or below each group average, and the standard deviation gives a broad description of that variability. It does not give the full distribution, identify outliers, or show whether the same participant’s values changed between periods. Those questions require details or data not included in the registry record.

How should the confidence interval be read?

A confidence interval expresses uncertainty around an estimate using a method with a stated long-run coverage property. In plain terms, it indicates a range of values that are reasonably compatible with the observed estimate under the method’s assumptions. A narrower interval indicates greater precision than a wider interval on the same scale. An interval that includes zero does not establish that the true difference is exactly zero; it indicates that zero is among the values compatible with the interval procedure. Nor does an interval that includes zero demonstrate equivalence.

The primary interval extends from -0.030 to 0.036. Its span includes both negative and positive possible differences, as well as zero. The registry does not state a threshold for clinical importance, so statistical uncertainty cannot be translated into a judgment about practical importance. The interval also does not account for uncertainty about unreported design and analysis choices.

What does the p-value add?

A p-value summarizes how unusual the observed result, or a result more extreme under a defined test statistic, would be if the null model and its assumptions held. It is not the probability that the null hypothesis is true, and a large p-value is not proof that there is no effect. The posted primary p-value is unadjusted and comes from a simple recalculation based on the outcome summaries. The registry lists no reported analyses, so the original test, model, and any adjustments are not reported in the registry record.

The recalculated comparison uses an approximate pooled standard deviation and group counts from the posted summaries. Such a calculation can offer a straightforward descriptive comparison, but it may not reproduce a planned crossover analysis. A crossover design can involve within-participant comparisons, period effects, or sequence effects. Whether and how these features were addressed is not reported in the registry record. The recalculation should therefore be understood as an unadjusted comparison of the available group summaries, not as evidence that any particular crossover model was used.

Why does variability matter?

More variability makes it harder to estimate a group mean precisely when the sample size is unchanged. In a continuous outcome, the standard deviation is one summary of that variability. The primary group standard deviations are both 0.115. The reported group counts are 96 and 95. These quantities jointly inform the uncertainty in a simple mean comparison, but they do not convey the full dependence structure that may arise when the same participants contribute measurements under both lenses.

Over-dispersion is a general concern when observed variability is greater than a model allows. If a model understates variability, its standard errors may be too small and its intervals too narrow. The registry does not report a model or an assessment of over-dispersion, so there is no basis for claiming that it occurred in this study. This is a general consideration for interpreting model-based results, not a finding about these data.

What do the recalculated results mean?

The recalculated estimates are simple, unadjusted comparisons from the posted summary statistics. They are useful for describing the arithmetic relationship between the reported group means and for illustrating the uncertainty under the calculation’s assumptions. They do not replace an analysis that uses participant-level crossover data, adjustment factors, or methods specified in a protocol. The registry does not report whether such an analysis was performed outside the posted record. The record also does not provide enough detail to verify the analysis population or to determine how incomplete measurements were handled.

All inferential methods rely on assumptions. For a simple continuous-outcome comparison, assumptions may concern independence, distributional behavior, and the way variability is estimated. In a crossover study, the relationship between observations from the same participant matters as well. The group summaries alone cannot establish whether these assumptions were met. Accordingly, the numerical results support a cautious description of the posted means and their calculated uncertainty, rather than a complete reconstruction of the trial’s original statistical analysis.

11. Confidence Intervals and Precision

The primary mean difference is 0.003 LogMAR, and the 95% confidence interval extends from -0.030 to 0.036. The interval includes zero, so the posted estimate is compatible with no average difference under the interval method. It also includes values on either side of zero, which means the estimate is not precise enough to determine the direction of the difference from these summaries alone.

The interval gives more information than the point estimate alone: it indicates the range of values compatible with the data and calculation assumptions. Its endpoints should not be treated as exact limits on the true difference. A confidence interval is a measure of statistical uncertainty, not a range that contains every individual eye’s outcome. It also does not account for unknown sources of uncertainty, such as unreported analysis choices or handling of missing measurements.

The registry does not report a clinical importance threshold for LogMAR. Thus, the interval cannot be classified as excluding or including a clinically meaningful difference on the basis of the record. An interval that crosses zero is not proof of equivalence, and a non-significant result does not establish that the lenses perform identically. A formal equivalence question would require a prespecified margin and an analysis appropriate to that objective; those details are not reported in the registry record.

For overall comfort, the posted mean difference is 0.8 units, with a 95% confidence interval from -5.337 to 6.937. That interval also spans zero and a range of values on either side. The registry gives no threshold for an important comfort difference. Both outcomes should therefore be interpreted as estimates with uncertainty, not as definitive classifications of sameness or difference.

12. 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 event counts. They are illustrations based on the observed effect, rather than the study’s original design calculation. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning scenario uses the stated fraction of the observed effect as the effect to detect. The original trial’s sample-size assumptions are not reported in the registry record.

The 80% power column gives the number of participants per arm that the illustration estimates would be needed for an 80% chance of detecting the specified effect under those assumptions, if that effect and the other assumptions were correct. The 90% power column gives the corresponding number for a 90% chance. These are planning probabilities for hypothetical future studies; they do not describe the probability that this completed study detected a real effect.

The display considers planning for 100%, 75%, and 50% of the observed effect. The smaller the effect one wishes to detect, the more participants the illustration requires, because a smaller signal is harder to distinguish from random variation. For example, under planning for 100% of the observed primary effect, the figures are 23,067 participants per arm for 80% power and 30,881 participants per arm for 90% power. These large illustrative counts reflect the small observed difference relative to the variability in the posted summaries. They are not recommendations for a future study and do not establish what sample size would be appropriate for a clinical objective.

The curve represents the same general planning relationship: requirements rise as the target effect becomes smaller, under the stated assumptions. The figures are planning illustrations, not observed power. Observed power is not an interpretation of the result’s precision; the confidence interval and the uncertainty in the estimate are more informative for describing what the posted data can distinguish.

13. 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 = 0.003; pooled standard deviation σ = 0.115.
2. n = 2 × (1.96 + 0.842)² × 0.115² / 0.003² = 23,067.0, rounded up to 23,067 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 <- 0.003                      # observed difference in means
sigma <- 0.115                     # 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(1412983)
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 = 23,067 (80% power), 30,881 (90% power)
 75% of observed effect: n per arm = 41,008 (80% power), 54,899 (90% power)
 50% of observed effect: n per arm = 92,268 (80% power), 123,521 (90% power)
power.t.test: 23067.9 
Simulated power at n = 23,067 per arm: 0.798 (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.

14. Multiplicity, Missing Data and Analysis Populations

The registry lists visual acuity as the primary outcome and overall comfort as a secondary outcome. It reports two outcome measures and no analyses. Testing or estimating more than one outcome raises a general multiplicity issue: the more comparisons considered, the greater the chance that at least one may appear notable by chance if each is interpreted without regard to the others. Common approaches include prespecifying a primary outcome, defining an ordered testing strategy, or adjusting statistical inference. The registry record does not report whether any multiplicity strategy was specified or used.

The primary outcome is identified in the record, which helps distinguish its role from the secondary measure. However, the posted p-values are unadjusted recalculations, and no reported analysis results are listed. The registry does not state whether there were additional analyses that were not posted, whether the primary analysis was adjusted for the crossover design, or whether the outcome hierarchy was part of an original statistical plan. Those details are not reported in the registry record, so the strength of formal inferences across outcomes cannot be fully assessed.

The record gives the primary analysis population as all eligible dispensed eyes, but does not describe the criteria for eligibility, the relationship between eyes and participants in the analysis, or whether all randomized participants were included. It lists outcome counts of 96 and 95 for visual acuity and 96 and 97 for comfort. The reasons for these different counts, any missing measurements, and the methods used to handle missing data are not reported in the registry record. It is therefore not appropriate to assume that observations were missing at random, that all participants completed every assessment, or that a particular imputation method was used.

For a crossover study, sequence, period, and within-participant structure can affect analysis choices. The registry does not report the sequence allocation, period-specific results, carryover assessment, washout details, or whether the primary analysis used paired information. These omissions do not demonstrate a flaw, but they limit an independent assessment of whether the posted summaries capture the intended design. The original statistical plan, including any interim analyses or stopping rules, is not reported in the registry record.

15. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The adverse-event record lists 99 participants at risk in each lens group. It records zero serious adverse events and zero other adverse events in both groups. No serious-event terms are listed. The death counts are not reported in the registry record.

These figures describe the counts entered in the registry for the stated groups; they should not be read as proof that no adverse events of any kind could occur. A zero count in a posted summary means that no events were recorded in that category for the listed group and record, not that risk is absent. The record does not provide event definitions, exposure time, details of monitoring, or a narrative account of how events were collected and classified.

The two groups are reported with the same number at risk, but the study is described as a crossover and the record does not explain how exposure to each lens was represented in the safety summaries. The figures therefore give a concise account of posted counts, not a full comparative safety analysis. They should be interpreted alongside the limited timeframe and the absence of additional safety detail in the registry record.

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

The posted primary result estimates a small average difference between the lens groups in high-contrast visual acuity at one week. Its confidence interval includes zero and allows for values in either direction. The result does not establish a clear average difference, but it also does not prove that the lenses are identical or equivalent. The record gives no clinical importance threshold with which to judge whether possible differences would matter.

The study’s stated purpose was to assess clinical feasibility and product performance. That context matters: the registry describes a specific comparison, in a particular study population, at a recorded timeframe. The findings should not be generalized automatically to other lenses, other populations, or longer periods of use. Enrollment was 100, while the posted outcome counts vary by endpoint and group; the registry does not explain those differences.

The comfort result offers additional information about a separate aspect of performance, but it is secondary and unadjusted. Its estimate and interval should not be treated as a confirmatory test of the primary result. The record lists no reported analyses and does not explain the original statistical plan, crossover analysis, or missing-data handling. The simple recalculations describe the posted summary statistics; they cannot recover unreported analyses or design details.

The serious and other adverse-event entries show zero recorded events in the listed groups, with 99 at risk in each. These entries are limited registry summaries and do not establish an absence of risk. Taken together, the posted data characterize the observed group summaries and their uncertainty. They do not support a claim of equivalence, a definitive judgment about clinical importance, or a broad conclusion about performance beyond the study conditions recorded.

17. Why This Trial Matters Statistically

This study illustrates why an estimated difference, its uncertainty, and the design context need to be considered together. The primary mean difference is close to zero, but the confidence interval extends to values on both sides of zero. A point estimate alone would hide that uncertainty; a p-value alone would not show the range of differences compatible with the data. The interval and the scale of the endpoint help describe the precision more directly.

It also illustrates why a non-significant result is not equivalent to evidence of sameness. An equivalence conclusion requires a defined margin and an analysis designed around that margin. The registry does not report either. The visual-acuity comparison therefore remains an estimate with uncertainty, rather than a formal conclusion that the two lenses perform equivalently.

The crossover label raises questions about analysis structure that are important for interpreting results. General crossover methods may use within-participant comparisons and consider period or sequence effects, but the registry does not describe the analysis or design details needed to assess those features. Simple recalculations from group summaries are transparent as unadjusted comparisons, yet they cannot reproduce an analysis that uses unposted participant-level information.

Finally, the planning illustrations show how sample-size requirements depend on the effect targeted and the assumptions used. They are not evidence about the study’s original design, nor do they measure the probability that the completed study detected an effect. Distinguishing a planning illustration from an original justification or an observed result is essential when reading registry-based statistical summaries.

18. 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’s design description is brief. Although the study is labeled randomized, single-masked, and crossover, the allocation sequence, masking details, periods, washout arrangements, and exposure schedule are not reported in the registry record. These details matter for understanding how outcomes from the two lenses were compared, particularly if participants contributed measurements under both lenses.

The primary endpoint is defined for all eligible dispensed eyes, but the relationship between eyes and participants is not described. Enrollment is 100, while the primary outcome counts are 96 and 95 and the comfort counts are 96 and 97. The record does not explain these differences, identify the reasons for any unavailable observations, or describe missing-data handling. Participant characteristics and further eligibility details are also not reported in the registry record.

The registry gives group means and standard deviations, but no participant-level data, period-specific summaries, or distributions. It lists no reported analyses. The original statistical model, any adjustment for the crossover structure, the multiplicity approach, and the sample-size justification are not reported. The unadjusted recalculations based on summary statistics are therefore not a substitute for the original analysis and may not capture design features that require individual-level information.

Both outcomes are recorded at one week, so the posted summaries address that timeframe rather than longer-term outcomes. The registry does not state a clinically important difference threshold for either measure. Safety entries provide event counts but not detailed definitions, collection methods, or exposure information. These limitations restrict the conclusions that can be drawn from the record; they do not, by themselves, establish that the study procedures or analyses were inadequate.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: A Study to Evaluate the Product Feasibility of a New Silicone Hydrogel Contact Lens — NCT01412983.
• Registry record last updated 2014-04-29; status last verified 2014-03.
• Results first posted 2014-04-29.
• 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.

22. Record Summary

The registry record describes a completed randomized, single-masked crossover study of an investigational Bausch + Lomb soft contact lens and a Ciba Vision Air Optix Aqua soft contact lens in people with myopia. Enrollment was 100, and the recorded study dates were 2011-08 to 2011-09.

The primary outcome was high-contrast visual acuity in LogMAR at one week, among all eligible dispensed eyes. The posted mean difference was 0.003, with a 95% confidence interval from -0.030 to 0.036 and an unadjusted p-value of 0.857. Overall comfort was the secondary outcome. The record lists zero serious and zero other adverse events in each group, with 99 at risk per group; death counts are not reported in the registry record.

No analyses are listed as reported. The original statistical plan, sample-size justification, crossover analysis details, and missing-data methods are not reported in the registry record. The posted recalculations describe the available group summaries and should be interpreted with those limitations in mind.