Pilot Study for Investigating the Effect of the Bruder Eye Hydrating Compress on Contact Lens Discomfort in Contact Lens Wearers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Pilot Study for Investigating the Effect of the Bruder Eye Hydrating Compress on Contact Lens Discomfort in Contact Lens Wearers (NCT02848222), a randomized na study. The primary outcome is Mean Change in the Duration of Subject-reported Comfortable Contact Lens Daily Wear Time (Hours Per Day).

2. Clinical Question

The study’s stated purpose was to assess whether daily warm-compress use was associated with improvement in ocular oil gland function and comfortable wearing time. The posted primary outcome addresses the latter: change in comfortable daily wearing time, measured in hours per day from baseline through one month. The results report the outcome by group and include a registry-reported overall analysis across all three groups.

This is a pilot comparison, not a broad test of all warm compresses or all contact lens wearers. The registry record describes three specific routines, including different frequencies of the Bruder compress and a twice-daily washcloth routine. The results therefore speak to those study groups and this reported measure; they do not establish how other routines, populations, or durations would compare.

3. Trial Design

This was a randomized, parallel-group study with no masking, listed as phase NA. The registry reports enrollment of 60 participants and a completed study. The listed study dates are 2016-07 for start and 2017-12 for primary completion. The sponsor was the University of Alabama at Birmingham.

Participants were assigned to one of three routines. Group 1 used the Bruder Moist Heat Compress twice daily: ten minutes in the morning before contact lens insertion and ten minutes in the evening after lens removal. Group 2 used the Bruder compress once daily for ten minutes in the evening after lens removal. Group 3 used a hot-water-warmed washcloth twice daily for ten minutes in the morning before lens insertion and ten minutes in the evening after lens removal. The study summary describes assessment after one month of daily application.

For the primary outcome, the registry describes 25 participants randomized to Group 1, with 18 completing; seven discontinued early, and one participant’s data were not used because of poor compliance, leaving 17 analyzed. Group 2 had 18 randomized and 17 completing. Group 3 had 17 randomized and completed. The posted outcome results use 17 participants in each group.

The record lists one outcome measure and one analysis. It reports an ANOVA across the three groups and also contains group-level results that permit simple, unadjusted pairwise recalculations. Details about the original sample-size justification, the study’s full statistical analysis plan, and any interim analyses are not reported in the registry record. The absence of masking and the reliance on a participant-reported outcome are relevant when interpreting the results.

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.

Overall Study

Analysis population for the primary outcome, as defined in the registry: In Gr1, 25 subjects were randomized, 18 subjects completed, 7 discontinued early and 1 subject's data was not used due to poor compliance resulting in 17 subjects analyzed. In Gr2, 18 subjects were randomized and 17 completed. In Gr3, 17 subjects were randomized and completed.

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: While 18 subjects in Group 1 completed all visits in the study, one subject's data was not used in the analysis due to poor compliance with instructions on using the Bruder compress and inaccessibility to an appropriate heating appliance for a prolonged period of time during the study period. Thus, only 17 subjects' data were analyzed.

6. Primary Endpoint

The registry lists the primary outcome as Mean Change in the Duration of Subject-reported Comfortable Contact Lens Daily Wear Time (Hours Per Day), measured over Baseline through 1 month.

The primary endpoint is mean change in the duration of subject-reported comfortable contact lens daily wear time, measured in hours per day from baseline through one month. It captures how long participants said they could comfortably wear their lenses each day, rather than a laboratory measure of lens performance or an objective assessment of eye function.

A change-from-baseline measure is used to describe how the reported wearing time changed during the study period. Comparing changes across the three groups can help distinguish the pattern observed during each assigned routine from the pattern observed in the other study groups. The endpoint is directly related to the study’s stated interest in comfortable wearing time. The study summary also mentions ocular oil gland function, but the posted primary outcome is comfortable wearing time.

The registry reports group means and standard deviations for this continuous outcome. A mean summarizes the group’s average reported change; a standard deviation describes how varied individual changes were around that group average. Neither quantity shows the range of every participant’s experience. The registry record does not give further detail about the exact instrument, diary, or measurement procedure used to capture wearing time, so those features cannot be assessed from the posted record.

7. Results Posted in the Registry

• Group 2: Once Daily Application of Bruder Compress: mean 8.50 versus 9.20 on control; difference -0.70 (95% CI -2.87 to 1.47), standardized effect d = -0.22; z-test p = 0.527.
• Group 3: Twice Daily Application of Warm Washcloth: mean 7.10 versus 9.20 on control; difference -2.10 (95% CI -3.98 to -0.22), standardized effect d = -0.75; z-test p = 0.029.

8. Statistical Interpretation

9. Statistical Methods Explained

The primary outcome is continuous: it is a duration measured in hours per day. The registry reports the mean and standard deviation for each group. A mean provides a concise summary of the group’s average change, while a standard deviation describes the spread of participant results around that average. A standard deviation is not the uncertainty in the mean; uncertainty in an estimated mean difference is conveyed more directly by a confidence interval.

What does the overall ANOVA test?

The registry reports an ANOVA across the three groups and gives p = 0.02. In general, an analysis of variance tests whether the observed pattern of group means is consistent with a common underlying mean, allowing for variation among participants. A small p-value indicates that the data would be relatively unusual under the test’s null model, if the model assumptions hold. It does not measure the size or importance of a difference, and it does not state which specific groups differ. The registry does not report the ANOVA’s test statistic, degrees of freedom, or a confidence interval for the overall test.

What are the pairwise recalculations?

The posted group summaries also allow simple, unadjusted comparisons of each of the other groups with the twice-daily Bruder group. These recalculations use group means and standard deviations to estimate a mean difference and its uncertainty. They are not adjusted for other variables and are not the registry-reported ANOVA. For once-daily Bruder compared with twice-daily Bruder, the recalculated mean difference is -0.7 hours per day; the 95% confidence interval runs from -2.868 to 1.468, with p = 0.527. For twice-daily washcloth compared with twice-daily Bruder, the recalculated mean difference is -2.1 hours per day, with p = 0.029. The reported interval for this latter contrast lies below zero.

The subtraction order matters: the reported comparisons express the other group relative to the twice-daily Bruder group. A negative estimate therefore means the other group’s posted mean is lower under that ordering. These simple contrasts do not replace the overall test. Nor do their unadjusted p-values account for the fact that multiple comparisons may be considered. The registry record does not report a multiplicity procedure, so the recalculated pairwise p-values should be interpreted with that limitation in mind.

Why might a confidence interval matter more than a p-value?

In general, a confidence interval shows a range of values compatible with the observed data under the method used. It conveys both the direction of the estimated contrast and its precision. A wide interval allows a broader range of possible differences than a narrow interval. If an interval includes zero for a mean difference, the data are compatible with no difference as well as with values on either side of zero, within the interval and under the model. That is the case for the recalculated once-daily versus twice-daily Bruder contrast. An interval entirely on one side of zero is more consistent with a difference in that direction under the calculation, but it does not establish a broadly applicable effect.

What can and cannot be verified?

The registry record names ANOVA as the reported method but does not give the full statistical plan or detailed modeling specifications. It does not report whether covariates were included, how missing outcomes were handled in the sponsor’s analysis, or whether assumptions were checked. The pairwise calculations are explicitly unadjusted recalculations from the posted summaries. Because the record flags a discrepancy, the sponsor’s own analysis takes precedence over those recalculations when describing the study’s reported analysis.

In general, analyses of means rely on assumptions about how observations behave, including independence and the suitability of the model for the outcome’s distribution. The record does not report diagnostic results, so it is not possible to evaluate those assumptions from the posted results. The small analyzed groups also mean that estimates and intervals may be sensitive to individual observations. These are interpretive considerations, not findings that a particular assumption was violated.

10. Confidence Intervals and Precision

The confidence intervals attached to the pairwise recalculations help show how much uncertainty remains around the estimated mean differences. For once-daily Bruder versus twice-daily Bruder, the recalculated difference is -0.7 hours per day, and its 95% confidence interval extends from -2.868 to 1.468. Because this interval includes zero, the posted summaries are compatible with no difference as well as with differences in either direction within the interval. The interval is broad relative to the estimate, so the contrast is not pinned down precisely by these data.

For twice-daily washcloth versus twice-daily Bruder, the recalculated mean difference is -2.1 hours per day, and the reported interval lies below zero. The result is more precise in direction under this unadjusted calculation than the interval for the once-daily versus twice-daily Bruder comparison. Still, its width reflects substantial uncertainty about the size of the contrast. The group sizes are small, and the calculation is based on posted summary statistics rather than individual participant data.

In general, a 95% confidence interval describes the range of values that would be compatible with the data under the statistical method and its assumptions. It is not a guarantee that the true value lies within the particular interval, and it does not capture every source of uncertainty, such as limitations in measurement or missing data. The registry does not post confidence intervals for its overall ANOVA result. These pairwise intervals are recalculated, not reported by the sponsor, and they should be considered alongside the discrepancy between those calculations and the sponsor’s own analysis.

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 accompanying sample-size display is a planning illustration based on the observed effect in each pairwise comparison, not the original study’s design. For this continuous outcome, the displayed quantities are participants per arm, not total events. The assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. The calculation considers detecting the stated fraction of the observed effect. The registry record does not report the trial’s original sample-size justification or its original planning assumptions.

The 80% power column gives the estimated number of participants per arm for a future study to have an 80% chance of detecting the specified effect under those assumptions, if the effect and model assumptions used for planning apply. The 90% power column uses a higher target probability of detecting that effect, and therefore generally requires more participants per arm. These values are prospective planning illustrations; this is not observed power.

Rows that plan for 75% or 50% of the observed effect assume a smaller effect to detect than the row based on 100% of the observed effect. Smaller effects are harder to distinguish from random variation, so they require more participants per arm under the same planning assumptions. The displayed curve should be read as another view of that planning relationship, not as a result observed in the completed trial.

These calculations are especially sensitive to the observed effect used as their starting point. The pairwise estimates come from small groups, and the comparison against washcloth differs from the comparison between the two Bruder schedules. Planning figures based on these estimates should therefore be treated as illustrations, not as a definitive sample-size recommendation or evidence that the trial had a particular probability of success.

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 = -0.700; pooled standard deviation σ = 3.225.
2. n = 2 × (1.96 + 0.842)² × 3.225² / -0.700² = 333.2, rounded up to 334 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 <- -0.699999999999999                      # observed difference in means
sigma <- 3.22490309931942                     # 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(2848222)
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 = 334 (80% power), 447 (90% power)
 75% of observed effect: n per arm = 593 (80% power), 793 (90% power)
 50% of observed effect: n per arm = 1,333 (80% power), 1,785 (90% power)
power.t.test: 334.1 
Simulated power at n = 334 per arm: 0.796 (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. Analyses Reported by the Sponsor

The registry’s own reported analysis is an ANOVA across all three groups, with p = 0.02. The posted record does not give the ANOVA estimate, confidence interval, or further test details. The pairwise estimates and p-values shown alongside it are simple, unadjusted recalculations from the posted group means and standard deviations; they are not a substitute for the sponsor’s analysis.

The recalculated comparison of once-daily Bruder with twice-daily Bruder gives a mean difference of -0.7 hours per day, a 95% confidence interval from -2.868 to 1.468, and p = 0.527. The recalculated comparison of twice-daily washcloth with twice-daily Bruder gives a mean difference of -2.1 hours per day and p = 0.029. The registry record flags a discrepancy between the reported analysis and the recalculation. Accordingly, the sponsor’s own analysis takes precedence when stating the trial’s reported statistical result.

The overall ANOVA addresses the three-group comparison, whereas the recalculations address specific pairs without adjustment. Those analyses ask different questions and need not produce the same p-value. However, the registry record does not explain the discrepancy or provide enough detail to determine its cause. It is therefore appropriate to report the sponsor’s overall result as posted and present the pairwise recalculations only as supplementary, unadjusted summaries.

14. Multiplicity, Missing Data and Analysis Populations

The record lists one primary outcome and one reported analysis, an ANOVA across the three groups. It also supports two pairwise recalculations comparing the other groups with the twice-daily Bruder group. The registry record does not report whether the sponsor planned additional comparisons, whether the ANOVA was followed by a specified post hoc procedure, or whether any multiplicity adjustment was applied. The recalculated pairwise p-values are unadjusted and should not be treated as if they account for testing multiple contrasts.

In general, considering multiple comparisons increases the chance that at least one result appears unusual by chance. Methods that adjust for multiplicity can address that issue, but the record does not identify such a method. It is not possible to infer from the posted p-values whether any adjustment was used in the sponsor’s overall analysis. The sponsor-reported ANOVA result and the unadjusted pairwise recalculations should remain clearly distinguished.

The primary outcome description gives group-specific analysis counts and notes early discontinuation and the exclusion of one Group 1 participant’s data for poor compliance. The posted outcome results include 17 participants per group. The registry record does not report a detailed missing-data method, whether the sponsor used an intention-to-treat population, how missing values were handled, or how the compliance-related exclusion was incorporated into the analysis. It also does not provide participant-level outcome data that would allow an independent evaluation of missingness or alternative analyses.

In general, missing data can affect a comparison if the participants with unavailable outcomes differ systematically from those whose outcomes are included. A sensitivity analysis can help assess how conclusions depend on assumptions about missing results, but such analyses are not reported in the registry record. The record also does not provide enough information to determine whether the analysis population was defined in advance or whether the reported outcome analysis followed a prespecified plan.

These reporting gaps limit assessment of analysis choices. They do not establish that a particular method was inappropriate; they mean that readers cannot verify the details from this registry record. The discrepancy flagged between the sponsor’s own analysis and the simple recalculations adds a further reason to keep the analysis types separate and avoid treating the recalculated contrasts as the definitive trial result.

15. 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 3% reporting threshold.

The posted safety figures report zero serious adverse events in each group, with 25 participants at risk in Group 1, 18 in Group 2, and 17 in Group 3. The record also reports zero participants affected by other adverse events in each group and zero deaths. These at-risk counts reflect the safety populations shown in the registry and are not identical to the 17 analyzed participants per group for the primary outcome.

These figures describe what was recorded in this study; they do not prove that no adverse event could occur with these routines. The groups were small, and the record gives no serious adverse event terms because none are listed. It does not provide further detail about how events were collected or classified, or about the duration of safety follow-up beyond the study summary. The safety results should therefore be read as a summary of recorded events in this completed pilot, not as a comprehensive assessment of risk.

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

The posted results describe three groups of contact lens wearers followed through the study’s one-month primary outcome period. Their reported mean changes in comfortable daily wearing time were 9.2 hours per day for twice-daily Bruder use, 8.5 hours per day for once-daily Bruder use, and 7.1 hours per day for twice-daily washcloth use. The registry’s overall ANOVA is reported with p = 0.02. Those findings summarize the data recorded for these study groups and this outcome.

The pairwise calculations add detail but are not the sponsor’s reported overall analysis. The once-daily versus twice-daily Bruder contrast has a confidence interval that includes zero, while the twice-daily washcloth versus twice-daily Bruder interval lies below zero. These recalculations are unadjusted, and the record flags a discrepancy between them and the sponsor’s analysis. The sponsor’s own analysis takes precedence.

These results do not establish how much comfortable wearing time any individual participant should expect, whether the routines would have the same results in other groups, or whether differences persist beyond the reported period. They also do not establish that one routine is superior in a broader clinical sense. The endpoint is participant-reported wearing time, and the registry record does not provide the measurement instrument or detailed missing-data and analysis procedures.

In general, a pilot study can describe observed patterns and inform planning for future research, but estimates from small groups can be uncertain. The sample-size display is a planning illustration based on observed effects, not evidence about the probability that the completed study would detect an effect. Taken together, the posted record offers a limited statistical account of a three-group comparison rather than a definitive answer for all contact lens wearers or warm-compress routines.

17. Why This Trial Matters Statistically

This trial is statistically instructive because it brings together three treatment routines, a continuous participant-reported outcome, an overall analysis, and pairwise comparisons. The overall ANOVA and the pairwise recalculations answer related but distinct questions. Keeping those questions separate prevents an overall p-value from being mistaken for evidence about each individual comparison.

The record also shows why effect estimates and confidence intervals add information beyond a p-value. The once-daily versus twice-daily Bruder estimate is -0.7 hours per day, with a confidence interval spanning zero and a p-value of 0.527. The twice-daily washcloth contrast has a different estimate and an interval lying below zero. The width and position of an interval help readers assess both direction and precision, while a p-value alone does not convey the range of plausible differences.

Small analyzed groups make transparent reporting especially important. The registry provides group means, standard deviations, analysis counts, and some information on discontinuation and compliance. It does not provide a full analysis plan, missing-data approach, or multiplicity details. Those omissions make it harder to evaluate how the reported results were produced and how the overall and pairwise analyses relate.

Finally, the sample-size illustrations show how planning depends on the effect chosen to detect: planning for a smaller effect requires more participants per arm. Because the display uses observed effects from this pilot, it should be read as a conditional planning exercise rather than a definitive design prescription. Together, these features make the record a useful example of why statistical interpretation depends on the analysis question, uncertainty, and completeness of reporting—not only on whether a p-value is below a threshold.

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.

Several limitations are specific to this record and study. The primary endpoint is self-reported comfortable contact lens wearing time, and the record does not identify the measurement instrument or provide further detail about how the daily duration was captured. Since the study was not masked, participants knew which routine they used. These design features are relevant to interpreting a reported outcome, though the record does not establish that they biased the results.

The groups were small: the primary outcome results include 17 analyzed participants in each group. In Group 1, the registry reports that seven of 25 randomized participants discontinued early and one participant’s data were not used because of poor compliance; 18 completed. Group 2 had 18 randomized and 17 completed, while Group 3 had 17 randomized and completed. The registry does not explain the missing-data method or report sensitivity analyses, so the effect of these exclusions and discontinuations on the estimates cannot be assessed from the posted record.

The record reports an overall ANOVA p-value but does not include its test statistic or confidence interval. It also does not provide a detailed statistical plan, multiplicity procedure, or rationale for the original sample size. The unadjusted pairwise recalculations differ from the sponsor’s reported analysis, and the record does not explain that discrepancy. The sponsor’s own analysis takes precedence; the recalculations are supplementary.

Finally, the primary outcome covers baseline through one month, and the registry record does not provide longer-term outcome results. The results are specific to the three listed routines and the enrolled study groups. They cannot, from this record alone, establish patterns for other populations, schedules, or follow-up periods.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Pilot Study for Investigating the Effect of the Bruder Eye Hydrating Compress on Contact Lens Discomfort in Contact Lens Wearers — NCT02848222.
• Registry record last updated 2018-05-17; status last verified 2018-05.
• Results first posted 2018-05-17.
• 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

This completed randomized, unmasked, parallel-group pilot enrolled 60 participants and compared three daily warm-compress routines in contact lens wearers reporting reduced comfortable wearing time. The primary outcome was mean change in self-reported comfortable contact lens daily wear time, in hours per day, from baseline through one month.

The posted outcome results include 17 participants in each group. Mean changes were 9.2 hours per day for twice-daily Bruder compress use, 8.5 hours per day for once-daily Bruder use, and 7.1 hours per day for twice-daily warm washcloth use. The registry reports an overall ANOVA p-value of 0.02. Simple unadjusted pairwise recalculations are also available, but the record flags a discrepancy; the sponsor’s own analysis takes precedence.

The record reports zero serious adverse events, zero other adverse events, and zero deaths in the listed safety groups. It does not report the original sample-size justification, full analysis plan, multiplicity procedure, or detailed missing-data method. The sample-size display is a planning illustration based on observed effects, not a report of the trial’s original design assumptions.