Evaluation of Contact Lenses and Conjunctival Staining in Normal Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Evaluation of Contact Lenses and Conjunctival Staining in Normal Patients (NCT00799422), a randomized na study. The primary outcome is Mean Circumlimbal Conjunctival Staining Score.

2. Clinical Question

3. Trial Design

The registry describes a randomized, double-masked crossover study of contact lens fit, lens parameters, and circumlimbal conjunctival staining in normal patients. The study enrolled 26 participants and is marked completed. The primary outcome population consists of participants who completed all study visits. The posted outcome data include 22 participants for each product condition; the registry record does not report why the outcome group is smaller than the enrollment total.

In a crossover design, participants receive more than one condition in a sequence, so comparisons can draw on measurements from the same people under different conditions. Here, the three care products were dispensed in randomized order. The descriptions state that each product was used for one week with a fresh pair of Acuvue Oasys contact lenses, with a 36-hour washout before each use. The registry record does not report the sequence-generation method, allocation concealment, or the roles of the people masked.

The primary outcome was measured at one week. Two secondary measures were changes from dispense at one week in lens base curve and lens diameter. The phase is listed as not applicable. The registry record does not report the original sample-size justification, a target enrollment rationale, or the detailed analysis plan for this crossover design. In particular, it does not describe how the analysis handled within-participant correlation, sequence, or possible period effects.

The result summaries are therefore best read as descriptive outcome data from the completed-visit group, with the recalculated comparisons interpreted cautiously. The posted record does not establish that these summary-statistic comparisons reproduce any planned crossover model.

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: In this 3-treatment, 3-period, 6-sequence crossover study, each subject received all 3 products in randomized order and used 1 product at a time for a duration of 1 week before switching to the next assigned product. A 36-hour washout preceded each usage period.

First Week of Wear

Reasons for not completing this period:

Second Week of Wear

Third Week of Wear

Analysis population for the primary outcome, as defined in the registry: This reporting group includes all participants who completed all study visits.

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Mean Circumlimbal Conjunctival Staining Score, measured over 1 week.

The primary endpoint is the mean circumlimbal conjunctival staining score at one week. Investigators assessed the bulbar conjunctiva with a slit-lamp and lissamine green ophthalmic dye. Staining was graded in four regions: nasal, temporal, inferior, and superior. Each region used a clinical scale from grade 0 for no staining to grade 3 for dense staining. The grades were summed, producing a total score from 0 to 12. The registry states that a lower score represents a more desirable outcome.

This endpoint captures the extent and grade of staining across multiple regions rather than relying on one eye region alone. A mean summarizes the average score in each product condition; the standard deviation describes how much individual scores varied around that average. Those group summaries do not show the distribution of individual scores or how each participant’s score changed from one product condition to another.

The outcome is relevant to the study’s stated focus on conjunctival staining during contact lens care product use. It should be interpreted as a measure on the stated grading scale, not as a direct measure of a broader clinical outcome. The registry record does not report a threshold for a clinically important difference or define how much change in the score would matter to participants.

7. Results Posted in the Registry

• Complete Easy Rub: mean 5.55 versus 6.39 on control; difference -0.84 (95% CI -2.40 to 0.72), standardized effect d = -0.32; z-test p = 0.291.
• Clear Care: mean 5.68 versus 6.39 on control; difference -0.71 (95% CI -1.96 to 0.54), standardized effect d = -0.34; z-test p = 0.265.

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.

Mean Change From Dispense (Day 0) in Lens Base Curve at 1 Week

• 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:
  • Complete Easy Rub: mean -0.27 versus -0.25 on control; difference -0.02 (95% CI -0.12 to 0.08), standardized effect d = -0.12; z-test p = 0.688.
  • Clear Care: mean -0.25 versus -0.25 on control; difference 0.00 (95% CI -0.09 to 0.09), standardized effect d = 0.00; z-test p = 1.000.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Complete Easy Rub and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Clear Care and the control. The interval gives the range of effects that remain compatible with the data.

Mean Change From Dispense (Day 0) in Lens Diameter at 1 Week

• 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:
  • Complete Easy Rub: mean 0.13 versus 0.15 on control; difference -0.02 (95% CI -0.08 to 0.04), standardized effect d = -0.19; z-test p = 0.528.
  • Clear Care: mean 0.14 versus 0.15 on control; difference -0.01 (95% CI -0.07 to 0.05), standardized effect d = -0.10; z-test p = 0.740.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Complete Easy Rub and the control. The interval gives the range of effects that remain compatible with the data.
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between Clear Care and the control. The interval gives the range of effects that remain compatible with the data.

The two secondary outcomes concern changes in lens base curve and lens diameter from dispense to one week. Across these measures, the product-condition means are close in the posted summaries, and the recalculated comparisons against ReNu MultiPlus are small relative to their uncertainty. The pattern is broadly consistent with the primary outcome in the limited sense that these summaries do not display a clear, precise separation among product conditions.

These secondary measurements address lens parameters rather than conjunctival staining, so they add a different kind of descriptive information. They should not be treated as confirmation of the primary result: similarity in lens measurements does not prove similarity in staining, and an uncertain staining comparison does not determine the lens-parameter results. The outcomes reflect distinct measurements and can have different sources of variability.

The registry record reports no analyses for the secondary outcomes. The numerical comparisons are recalculated and unadjusted, rather than reported results from a prespecified crossover analysis. The record does not state whether the secondary outcomes were designated confirmatory, how many analyses were planned, or whether multiplicity was addressed. This limits the strength of any inference based on individual secondary comparisons.

General explanation: secondary outcomes can help describe a study and can suggest questions for further research, but conclusions based on multiple unadjusted comparisons are more vulnerable to chance findings. The appropriate weight depends on whether the outcomes and analysis were prespecified, how many comparisons were considered, and whether the statistical method matches the design. Those details are not reported in the registry record. The overall secondary pattern is therefore best read as descriptive context alongside, rather than independent proof of, the primary outcome.

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

• Mean Change From Dispense (Day 0) in Lens Base Curve at 1 Week
• Mean Change From Dispense (Day 0) in Lens Diameter at 1 Week

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous: it is a numerical score formed by summing grades across eye regions. The registry reports a mean and standard deviation for each product condition. In general, a mean describes the center of a group’s observed values, while a standard deviation describes their spread. Neither summary alone shows the full score distribution or the pattern of each participant’s repeated measurements.

The registry identifies ReNu MultiPlus as the comparison reference. The recalculated mean differences subtract the ReNu MultiPlus mean from the mean for the named product. Thus, a negative difference indicates a lower observed average score in that product condition. For this endpoint, lower scores are described as more desirable. This direction is a feature of the score definition; it does not by itself establish clinical importance.

The comparison estimates are recalculated unadjusted results based on posted group summaries. They include a mean difference, a confidence interval, and an unadjusted p-value. General explanation: a confidence interval describes a range of effect values compatible with the data under the calculation’s assumptions. A p-value measures how unusual the data would be under a specified no-difference model; it is not the probability that there is no effect, and it does not measure the size or importance of an effect.

The calculations use summary means and standard deviations, but the study is a crossover. General explanation: a crossover analysis can use the fact that outcomes from the same participant across conditions are paired. The precision of a paired comparison depends partly on how strongly the repeated measurements within a participant are related. The registry record does not report this correlation or a detailed crossover analysis. Consequently, the posted summaries are not enough to reconstruct a paired analysis or assess potential sequence and period effects. The recalculated comparisons should not be mistaken for a reported crossover-model result.

The unadjusted p-values are not described as adjusted for multiple comparisons. There are two primary comparisons against ReNu MultiPlus, along with two secondary outcome measures. General explanation: when several outcomes or comparisons are examined, the chance of at least one apparently unusual result can increase if each is assessed separately. Adjustment methods can address that issue, but the registry record does not report whether an adjustment was planned or used. The p-values should therefore be read as unadjusted rather than as a family-wise assessment.

The posted primary outcome population includes participants who completed all study visits. This is a complete-visit reporting group, not necessarily every participant enrolled. The record does not report participant-level missingness, reasons for non-completion, imputation, or sensitivity analyses. General explanation: missing outcomes can affect both the representativeness of a reported group and the uncertainty of comparisons, depending on why they are missing and how they are handled.

Two additional continuous measures are reported: change from dispense in lens base curve and lens diameter at one week. Their means and standard deviations are descriptive summaries. The registry record reports no analyses for these outcomes. The calculated comparisons are also unadjusted, and should be considered exploratory rather than definitive, especially in the absence of a stated analysis plan or multiplicity strategy.

Finally, the registry lists enrollment as 26, while the outcome summaries contain 22 observations in each product condition. In a crossover, the same participants may contribute to more than one condition, so these condition counts should not be added to infer the number of unique participants. The registry record does not explain the difference between enrollment and the completed-visit outcome group.

11. Confidence Intervals and Precision

The primary mean differences are estimated with limited precision. For Complete Easy Rub, the recalculated difference from ReNu MultiPlus is -0.84, with a confidence interval from -2.4 to 0.720. For Clear Care, the difference is -0.71, with a confidence interval from -1.959 to 0.539. Both intervals include zero, so each is compatible with no mean difference under the calculation’s assumptions. Each also spans differences in either direction, so the direction and size of a possible difference are not tightly determined.

General explanation: a confidence interval is useful because it communicates uncertainty around an estimate rather than presenting the point estimate as exact. A narrower interval indicates greater precision, while a wider interval leaves more possible effect values compatible with the data. The interval does not assign a probability to the particular effect being inside it; its interpretation depends on the statistical procedure and assumptions.

The posted standard deviations are 2.3 for ReNu MultiPlus, 2.94 for Complete Easy Rub, and 1.91 for Clear Care, with 22 observations in each condition. The variation in scores and the relatively small completed-visit group contribute to the uncertainty. Since this was a crossover study, the repeated observations within participants may also matter for precision. The registry record does not report the within-participant correlation needed to assess that aspect of uncertainty.

These intervals come from unadjusted recalculations using posted summaries, not a reported crossover analysis. They do not account for any unreported multiplicity procedure. The record also does not report a clinically important difference threshold, so the intervals cannot be used to decide whether a particular possible difference would matter clinically. They are most useful as a transparent description of statistical uncertainty around the recalculated comparisons.

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 events. The listed illustrations use a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They consider detecting 100%, 75%, or 50% of the observed effect. These are planning assumptions for the illustrations; the trial’s original sample-size assumptions and justification are not reported in the registry record.

The 80% power column describes the number of participants per arm that a hypothetical study would need, under those assumptions, to have an 80% chance of detecting the specified effect if that effect were the true one. The 90% power column gives the corresponding planning target for a 90% chance. Higher planned power generally requires more participants under otherwise similar assumptions. The figures are not the number enrolled or analyzed in this trial.

The rows for smaller fractions of the observed effect require more participants because smaller differences are harder to distinguish from random variation. The entries use the observed effect as the starting point for hypothetical planning; they are not evidence that such an effect is real or clinically important. Different assumptions about the effect, variability, study design, or analysis could produce different planning estimates. Since the trial is a crossover, the two-arm equal-allocation illustration does not by itself represent a complete design-specific sample-size analysis for the study.

This is not observed power. It is a planning illustration based on the posted effect estimates, not an assessment of the probability that the completed trial detected an effect.

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 = -0.840; pooled standard deviation σ = 2.639.
2. n = 2 × (1.96 + 0.842)² × 2.639² / -0.840² = 155.0, rounded up to 155 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 <- -0.84                      # observed difference in means
sigma <- 2.63946964369738                     # 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(799422)
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 = 155 (80% power), 208 (90% power)
 75% of observed effect: n per arm = 276 (80% power), 369 (90% power)
 50% of observed effect: n per arm = 620 (80% power), 830 (90% power)
power.t.test: 156 
Simulated power at n = 155 per arm: 0.794 (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 identifies one primary outcome and two secondary outcomes. It does not report a multiplicity strategy, such as a prespecified hierarchy among outcomes or an adjustment across comparisons. The posted comparison p-values are unadjusted recalculations. They should not be interpreted as if they were adjusted for the number of outcomes or comparisons considered. The registry record does not report how many additional analyses may have been conducted outside the posted entry.

The record lists no reported analyses for the primary and secondary measures. It provides group means and standard deviations, from which simple comparisons have been recalculated, but it does not give a detailed statistical analysis plan. The original method for analyzing the randomized crossover, including how repeated measurements, treatment sequence, or period were handled, is not reported in the registry record. Nor is a model-based estimate from a sponsor analysis reported in this entry.

The primary reporting population is participants who completed all study visits. The registry record does not report how many participants failed to complete visits, why any participant did not complete, or whether all enrolled participants were included in any other analysis population. Missing-data methods, imputation, and sensitivity analyses are not reported in the registry record. The condition summaries include 22 observations each, but that count does not explain the outcome status of all 26 enrolled participants.

These gaps matter because the interpretation of repeated-measure comparisons depends on both the analysis method and the relation between missingness and outcomes. General explanation: missing data can affect estimates if the likelihood of having an observed outcome is related to the outcome or treatment experience. No missing-data mechanism can be inferred from the posted record. Likewise, no claim about prespecification, interim analyses, or adjustment can be made from information that is not reported in the registry record.

In this setting, the most cautious reading is to treat the posted group summaries as descriptive and the recalculated comparisons as unadjusted. The registry record does not establish whether the full planned statistical procedures would yield the same estimates or uncertainty.

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 5% reporting threshold.

Most frequent serious adverse event terms

Serious events with the highest arm-level rate: pulmonary embolism (4.5%).

The serious adverse event summaries list 22 participants at risk in each product condition. One serious adverse event is recorded for ReNu MultiPlus, and none are recorded for Complete Easy Rub or Clear Care. The registry lists pulmonary embolism among the top serious adverse event terms at 4.5%. It does not provide enough detail in this entry to establish a causal relationship between a product and an event.

No other adverse events are recorded in the posted group summaries. Death counts are not reported in the registry record. These figures describe the adverse event entries for the listed groups; they do not establish that no other events occurred outside the reported data.

General explanation: small groups provide limited information about uncommon events, and a zero count in a group does not establish absence of risk. The counts should be read as a compact record of what was reported, not as a comparative safety estimate. The registry record does not report additional detail about event timing, severity beyond the serious classification, relatedness assessments, or a formal safety comparison.

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

The posted primary outcome means are 6.39 for ReNu MultiPlus, 5.55 for Complete Easy Rub, and 5.68 for Clear Care, based on 22 observations in each condition among participants who completed all visits. The recalculated unadjusted differences are -0.84 for Complete Easy Rub versus ReNu MultiPlus and -0.71 for Clear Care versus ReNu MultiPlus. The negative estimates correspond to lower average staining scores, which the registry describes as more desirable.

Both confidence intervals include zero, and the unadjusted p-values are 0.291 and 0.265. The results therefore do not provide a clear statistical distinction between either product and ReNu MultiPlus in these recalculated comparisons. This is not proof that the products are equivalent, nor proof that any difference is absent. The intervals remain compatible with effects in either direction.

The study is a randomized crossover, but the registry entry does not report a detailed crossover analysis. The posted recalculations use summary statistics and do not incorporate unreported within-participant correlations or other design features. This makes the comparison estimates less definitive than a clearly reported analysis tailored to the randomized crossover could be. The registry record also does not report an equivalence margin, a threshold for clinical importance, or an adjustment for multiple comparisons.

The secondary lens measurements provide descriptive context but do not resolve the uncertainty in the primary outcome. Likewise, the serious adverse event figures are descriptive and are too limited to support a broad comparative safety conclusion. The completed-visit population and the unreported reasons for the difference between enrollment and outcome counts also constrain interpretation.

Overall, the record describes observed staining and lens-measurement summaries under the three product conditions. It does not establish a definitive difference, equivalence, clinical importance, or causal safety conclusion. The most defensible interpretation is bounded by the uncertainty in the estimates and by the statistical and missing-data details that are not reported in the registry record.

17. Why This Trial Matters Statistically

This trial is statistically notable because it uses a randomized crossover design to compare several product conditions within a study focused on both staining and lens parameters. Repeated measurements can be informative: when participants serve as their own comparison, stable differences between people may be less influential. But that potential advantage depends on an analysis that uses the paired structure and reports the relevant uncertainty.

The registry entry makes the design and outcome summaries visible, but it does not report the detailed analysis needed to assess how the crossover structure was handled. In particular, within-participant correlations, sequence effects, period effects, and the original sample-size rationale are not reported. The recalculated comparisons provide an accessible descriptive benchmark, while also illustrating why summary means alone cannot reconstruct all design-specific analyses.

The estimates are modest in the score’s units and have confidence intervals that include zero. These features underscore the difference between a point estimate and a precise conclusion. The secondary measures also show why multiple outcome reporting needs context: results across related outcomes can be informative, but unadjusted comparisons without a stated plan should not be treated as a collection of confirmatory tests.

For biostatisticians and clinical researchers, the record highlights the importance of reporting analysis populations, handling of repeated measures, missing-data methods, multiplicity decisions, and sample-size assumptions. Those details help readers distinguish an outcome summary from a design-appropriate inferential result. The trial’s posted information supports careful description, while several key elements needed for stronger statistical interpretation are not reported in the registry record.

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 posted primary analysis group is restricted to participants who completed all study visits. Although 26 participants were enrolled, 22 observations are reported for each product condition. The registry record does not report the reasons for this difference, the number of participants with incomplete outcomes, or whether missingness differed by condition. This limits assessment of potential selection effects.

The crossover structure is a central trial-specific limitation for interpreting the recalculated comparisons. The registry describes randomized product order and washout, but does not report the period-by-period outcome data, within-participant covariance, or a model accounting for sequence and period. The recalculated comparisons from condition-level summaries cannot capture all information from repeated measurements. The record also does not report whether carryover was assessed.

The product descriptions state that each product was used for one week with a fresh pair of Acuvue Oasys contact lenses, with a 36-hour washout preceding use. The registry record does not report fuller details about adherence, protocol deviations, or how such issues were handled in the outcome analysis. Further eligibility characteristics beyond the normal-patient description are not reported in the registry record, limiting assessment of how broadly the results apply.

There is no reported clinical-importance threshold for the staining score, and no multiplicity strategy is described for the primary comparisons and secondary outcomes. The analysis plan, original sample-size justification, and missing-data methods are not reported in the registry record. These gaps, together with the modest completed-visit group and the imprecision of the comparisons, argue for treating the posted results as descriptive rather than definitive.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Evaluation of Contact Lenses and Conjunctival Staining in Normal Patients — NCT00799422.
• Registry record last updated 2012-11-16; status last verified 2012-11.
• Results first posted 2012-11-16.
• 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, double-masked crossover study of contact lens care products in normal patients. The study enrolled 26 participants. The primary outcome summaries include 22 participants per product condition among those who completed all study visits.

The primary measure was mean circumlimbal conjunctival staining score at one week, with lower scores described as more desirable. The registry also reports changes in lens base curve and lens diameter. ReNu MultiPlus is the comparison reference for the posted recalculated comparisons.

The primary recalculated differences favor lower average scores for Complete Easy Rub and Clear Care relative to ReNu MultiPlus, but both confidence intervals include zero. The registry record does not report a detailed crossover analysis, multiplicity method, missing-data approach, or original sample-size rationale. The findings are therefore best read as descriptive estimates with substantial uncertainty.