Efficacy of Zylet vs. Lotemax for the Treatment of Ocular Surface Inflammation/MGD/Blepharitis: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Efficacy of Zylet vs. Lotemax for the Treatment of Ocular Surface Inflammation/MGD/Blepharitis (NCT01456780), a randomized phase 4 study. The primary outcome is Ocular Surface Disease Index.

2. Clinical Question

3. Trial Design

The registry describes a Phase IV, randomized, quadruple-masked, parallel-group trial sponsored by Massachusetts Eye and Ear Infirmary. The brief summary calls it a single-site study. Enrollment is listed as 60, and the status is completed. The registry dates the study start to 2011-08 and primary completion to 2013-03.

Three arms are described: Zylet, Lotemax and Bausch & Lomb lubricant drops. The Zylet arm received loteprednol/tobramycin, the Lotemax arm received loteprednol, and the lubricant arm received artificial tears. Each arm description specifies dosing twice a day for 4 weeks. The registry identifies random allocation and a parallel model, but details of sequence generation, allocation concealment, the masking procedures, and who was masked are not reported in the registry record.

The brief summary says efficacy was to be assessed using in-vivo confocal microscopy, corneal fluorescein staining, grading of meibomian gland dysfunction and a validated ocular symptom assessment questionnaire. The posted primary outcome is OSDI at the Week 4 time point. Although four outcome measures are listed, the details and results for the other measures are not reported in the registry record. The record does not describe visit schedules beyond the stated primary time point and treatment duration, nor does it explain how the posted outcome group sizes relate to enrollment.

This design allows the posted OSDI means to be compared across the randomized treatment arms, but the available registry information does not establish how all trial conduct or analysis decisions were implemented. The original protocol, participant flow, adherence information and analysis populations 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.

Overall Study

Reasons for not completing this period:

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 Ocular Surface Disease Index, measured over Week 4 Time Point.

The primary endpoint is the Ocular Surface Disease Index (OSDI) at the Week 4 time point. OSDI is a questionnaire intended to measure symptoms of dry eye disease. Its 12 questions rate symptoms from 0 to 4, with higher responses indicating symptoms present more often. The registry describes an overall scale from 0 to 100, where 0 indicates no dry-eye symptoms and 100 indicates severe dry-eye symptoms.

The score is calculated from the answers to the questions that were completed. The registry’s description says the individual values are added, multiplied by 25, and divided by the number of questions answered. This means the score reflects reported symptoms rather than a direct examination of ocular surface signs. The brief summary separately mentions clinical and imaging assessments, but the primary posted outcome is the questionnaire score.

Patient-reported symptom measures can capture aspects of a condition that may not be represented by clinical grading alone. In general, a mean score provides a summary of the group’s responses, while the spread of scores indicates how variable those responses are. The posted outcome is reported as a mean with a standard deviation. The registry record does not report a threshold for a clinically important OSDI change or explain how missing questionnaire answers were handled.

7. Results Posted in the Registry

• Lotemax: mean 46.40 versus 56.60 on control; difference -10.20 (95% CI -26.09 to 5.69), standardized effect d = -0.43; z-test p = 0.208.
• Bausch & Lomb Lubricant Drops: mean 48.40 versus 56.60 on control; difference -8.20 (95% CI -21.69 to 5.29), standardized effect d = -0.40; z-test p = 0.234.

8. Statistical Interpretation

9. Statistical Methods Explained

The posted outcome is continuous: OSDI is summarized using a mean and standard deviation for each arm. The comparisons are expressed as mean differences, with Zylet as the reference. In general, a mean difference is calculated by subtracting the reference-arm mean from the comparison-arm mean. A negative value in these comparisons indicates that the comparison arm had a lower observed mean OSDI score than Zylet. Because higher OSDI scores correspond to more severe symptoms, that direction describes the observed score pattern, not a causal or clinical conclusion on its own.

What does the mean summarize?

A group mean describes the average score among the participants contributing to that outcome summary. It does not show whether most individuals had scores close to the mean, whether responses clustered in subgroups, or how scores changed for individuals over time. The standard deviation describes variation among the recorded scores around the group mean. It is not the standard error of the mean and should not be interpreted as a confidence interval.

The registry reports Week 4 mean OSDI values of 56.6 for Zylet, 46.4 for Lotemax, and 48.4 for Bausch & Lomb Lubricant Drops. The corresponding standard deviations are 22.4, 24.8 and 18.9. The outcome group sizes are 17, 17 and 20, respectively. These summaries describe the posted outcome data; they do not explain whether participants missing the endpoint were excluded, imputed, or handled another way.

How should the mean differences be read?

The comparison estimates are -10.2 for Lotemax versus Zylet and -8.2 for Bausch & Lomb Lubricant Drops versus Zylet. A mean difference retains the scale of the endpoint, so these estimates are in OSDI units. In general, the sign indicates direction and the magnitude indicates the distance between the reported group means. The registry record does not report a threshold for interpreting an OSDI difference as clinically important, so the estimates should not be labeled important or unimportant based only on their numerical size.

What does a confidence interval express?

In general, a confidence interval describes uncertainty around an estimate under the assumptions of the statistical method. It gives a range of values reasonably compatible with the observed data and method; it does not mean that the true value has a particular probability of lying in that specific calculated interval. The reported intervals are -26.09 to 5.686 for Lotemax versus Zylet and -21.69 to 5.29 for Bausch & Lomb Lubricant Drops versus Zylet. Both include zero, the value corresponding to no mean difference. Their breadth reflects uncertainty in estimating the between-arm difference from the posted summaries.

What does a p-value express?

The unadjusted p-values are 0.208 for Lotemax versus Zylet and 0.234 for Bausch & Lomb Lubricant Drops versus Zylet. In general, a p-value describes how unusual data at least as discordant with a specified null model would be if that model and the test assumptions held. It is not the probability that the null model is true, nor a measure of the size or clinical relevance of a difference. These are explicitly unadjusted values; the registry record does not report a multiplicity adjustment or a sponsor analysis to compare against them.

The calculations are unadjusted recalculations based on the posted means, standard deviations and group sizes. In general, such summary-statistic comparisons do not account for covariates or additional design features unless those are incorporated in the method. The registry record does not report the original statistical analysis plan, the test used for the primary endpoint, covariate adjustment, handling of missing data, or the analysis population. It also does not report interim analyses or a sample-size justification. The posted statistics should therefore be read as a limited, unadjusted comparison, not as a reconstruction of every planned or performed analysis.

10. Confidence Intervals and Precision

The confidence intervals convey substantial uncertainty about the Week 4 mean differences. For Lotemax versus Zylet, the estimate is -10.2 OSDI units and the 95% confidence interval ranges from -26.09 to 5.686. For Bausch & Lomb Lubricant Drops versus Zylet, the estimate is -8.2 OSDI units and the 95% confidence interval ranges from -21.69 to 5.29. Each interval includes zero, so the posted data are compatible with no mean difference as well as with a range of negative or positive differences.

In general, a wider interval indicates less precision about the size of an effect. Precision depends on features such as the variability of the outcome and the amount of information available for the comparison. The posted outcome group sizes are 17 for Zylet, 17 for Lotemax and 20 for Bausch & Lomb Lubricant Drops, and the reported standard deviations indicate variation in OSDI scores within each arm. The record does not report a target precision or a clinically important difference against which these intervals could be judged.

A confidence interval is not a guarantee that every value in its range is equally plausible, and it does not convert an uncertain estimate into a conclusion about clinical importance. The ranges also concern the mean difference, not the range of individual participants’ scores. The registry record gives no adjusted confidence intervals and no separate inferential results for the other listed outcomes. These intervals should therefore be interpreted as uncertainty around the unadjusted Week 4 OSDI comparisons only.

11. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for 80% power and participants per arm for 90% power. They are planning illustrations based on the observed effect, not the trial’s original design assumptions. The stated assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, a normal approximation, and an effect to detect set to the stated fraction of the observed effect. These sample-size figures are not observed power.

For Lotemax versus Zylet, planning for 100% of the observed effect gives 85 participants per arm for 80% power and 113 participants per arm for 90% power. Planning for 75% of the observed effect gives 150 participants per arm for 80% power and 201 participants per arm for 90% power. Planning for 50% of the observed effect gives 338 participants per arm for 80% power and 452 participants per arm for 90% power.

For Bausch & Lomb Lubricant Drops versus Zylet, planning for 100% of the observed effect gives 99 participants per arm for 80% power and 133 participants per arm for 90% power. Planning for 75% of the observed effect gives 176 participants per arm for 80% power and 236 participants per arm for 90% power. Planning for 50% of the observed effect gives 396 participants per arm for 80% power and 530 participants per arm for 90% power.

In general, the 80% and 90% columns describe the planned probability of detecting the specified effect under the assumptions if that effect is present. The higher-power target requires more participants in these illustrations. The smaller the effect targeted relative to the observed effect, the more participants are needed. These calculations are not a report of the study’s actual design justification; that justification and its original assumptions are not reported in the registry record.

12. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -10.200; pooled standard deviation σ = 23.630.
2. n = 2 × (1.96 + 0.842)² × 23.630² / -10.200² = 84.3, rounded up to 85 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 <- -10.2                      # observed difference in means
sigma <- 23.6304887803871                     # 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(1456780)
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 = 85 (80% power), 113 (90% power)
 75% of observed effect: n per arm = 150 (80% power), 201 (90% power)
 50% of observed effect: n per arm = 338 (80% power), 452 (90% power)
power.t.test: 85.2 
Simulated power at n = 85 per arm: 0.800 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

13. Multiplicity, Missing Data and Analysis Populations

The registry lists four outcome measures, but the posted results include the primary OSDI outcome and no posted secondary results. The registry record reports no analyses. It does not describe a statistical analysis plan, identify a hierarchy among outcomes, or state whether the primary comparison was prespecified in its reported form. The analysis population for the endpoint is also not reported in the registry record.

Multiplicity arises when several outcomes or comparisons are assessed. In general, considering many statistical tests can increase the chance of at least one apparently unusual result even when there are no true effects. Statistical approaches can account for that issue, but the registry record does not report whether any adjustment, testing hierarchy, or other multiplicity strategy was planned or used. The posted p-values are unadjusted, so they should not be treated as multiplicity-adjusted evidence.

The available record does not describe missing questionnaire data, exclusions, withdrawals, adherence, or the handling of incomplete OSDI responses. Although the OSDI description explains how completed answers contribute to a score, that does not establish how missing items or missing visits were treated in the analysis. The analysis population—such as whether the reported summaries include all randomized participants or a subset—is not reported in the registry record.

Details of randomization implementation, covariate adjustment, model selection, interim analyses and sensitivity analyses are also not reported in the registry record. Without those details, the recalculated comparisons should be understood as unadjusted summaries of the posted data, not as a substitute for a complete protocol-based analysis. This limits assessment of whether the reported comparisons follow the trial’s original statistical plan.

14. Safety Results

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

Deaths

Other (non-serious) adverse events

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

Most frequent non-serious adverse event terms

The serious adverse event figures list 20 participants at risk in each of the Zylet, Lotemax and Bausch & Lomb Lubricant Drops groups. The number affected by serious adverse events is 0 in each group, and deaths are listed as 0 in each group. The record lists no top serious-event terms.

These figures describe the registry’s posted serious-event counts for the stated groups. They do not establish that no other adverse events occurred: the separate other-adverse-event counts affected are 2 for Zylet, 1 for Lotemax and 2 for Bausch & Lomb Lubricant Drops. The registry record does not provide event descriptions, severity details, timing, or an explanation of how events were attributed to treatment. It also does not explain why the safety counts at risk differ from the outcome group sizes.

In general, a zero count in a study record means no event was reported in that category among the stated group, not that the risk is absent. The safety figures should be read as descriptive counts, with the limited follow-up and reporting details available in the record. They do not support a broader safety comparison beyond the events and groups recorded.

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

The posted Week 4 OSDI means were lower in the Lotemax and lubricant arms than in the Zylet arm. The unadjusted mean differences were -10.2 for Lotemax versus Zylet and -8.2 for Bausch & Lomb Lubricant Drops versus Zylet. Both confidence intervals include zero, and the unadjusted p-values are 0.208 and 0.234, respectively. The data therefore leave considerable uncertainty about the size and direction of the underlying mean differences.

These results do not establish that one treatment is better, worse, or equivalent to another. A failure to distinguish the means with these estimates is not proof that the treatments have the same effect. Conversely, the observed lower means in the comparison arms do not by themselves establish a treatment benefit. The registry record does not report a clinically important OSDI threshold, so the clinical importance of the estimates cannot be determined from these summaries alone.

The endpoint is a self-reported symptom measure at the Week 4 time point. It does not by itself describe changes in the other clinical and imaging measures named in the brief summary. Results for those measures are not reported in the registry record. The record also does not provide the analysis population, missing-data methods or a complete analysis plan, all of which matter when interpreting a trial result.

The conclusions that can be drawn are therefore narrow: the posted OSDI summaries describe the observed group means, variability and unadjusted mean differences at Week 4. They do not establish effects on other outcomes, durability beyond the stated time point, or implications beyond the trial’s recorded population and setting.

16. Why This Trial Matters Statistically

This trial illustrates why a difference between observed group means is only one part of statistical interpretation. The point estimates favor lower OSDI scores in the Lotemax and lubricant groups relative to Zylet, but the confidence intervals include zero and extend across values in both directions. Reporting the estimate together with its interval makes the uncertainty visible rather than reducing the interpretation to the direction of the means or a p-value alone.

The endpoint is a patient-reported symptom score, while the brief summary also names clinical grading and imaging outcomes. This distinction matters: different outcome types may capture different aspects of ocular surface disease, and a result on a questionnaire cannot stand in for unreported findings on other measures. The registry lists four outcome measures but does not report secondary results or an analysis plan, leaving the broader outcome picture incomplete.

The sample-size illustrations also show how planning changes with the effect targeted. Under the stated assumptions, smaller fractions of the observed effect require more participants per arm for the same power target. Such illustrations help explain the relationship between effect size, precision and planning, but they are not the study’s original justification and do not describe observed power.

Finally, the record’s gaps around missing data, analysis populations, multiplicity and randomization implementation are statistically important. They limit how fully readers can evaluate the path from trial conduct to the posted estimates. The study is therefore a useful example of interpreting effect estimates cautiously when registry information provides group summaries but limited detail about the analysis process.

17. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The posted OSDI outcome summaries include 17 participants in the Zylet arm, 17 in the Lotemax arm and 20 in the Bausch & Lomb Lubricant Drops arm. The registry lists enrollment as 60 but does not explain the relationship between enrollment and the outcome group sizes. Participant flow, exclusions and reasons for missing outcome data are not reported in the registry record.

The primary endpoint is reported at Week 4. Although treatment is described as lasting 4 weeks, longer-term outcome data are not reported in the registry record. The brief summary names additional clinical and imaging assessments, but their results are not posted in the information available for this analysis. The record also lacks a stated threshold for clinically important OSDI differences.

The brief summary describes a single-site study, which may limit how readily its findings can be generalized to other settings. Further details about eligibility, baseline characteristics, treatment adherence, randomization implementation and masking procedures are not reported in the registry record. The original sample-size justification and statistical analysis plan are also not reported.

Only unadjusted comparisons can be described from the posted summaries. Missing-data methods, analysis populations, covariate adjustment, multiplicity handling and interim analyses are not reported in the registry record. These limitations restrict interpretation of the uncertainty and prevent a full assessment of whether the posted analysis followed the original plan.

18. Related Tutorials

19. Related Statistical Calculators

20. Sources

• ClinicalTrials.gov: Efficacy of Zylet vs. Lotemax for the Treatment of Ocular Surface Inflammation/MGD/Blepharitis — NCT01456780.
• Registry record last updated 2017-08-01; status last verified 2017-07.
• Results first posted 2017-06-19.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

21. Record Summary

The registry record describes a completed Phase IV, randomized, quadruple-masked, parallel trial sponsored by Massachusetts Eye and Ear Infirmary. The brief summary calls it a single-site study. Enrollment is listed as 60, with study start in 2011-08 and primary completion in 2013-03.

The three arms were Zylet, Lotemax and Bausch & Lomb Lubricant Drops, each described as twice-daily treatment for 4 weeks. The primary outcome was OSDI at the Week 4 time point. Posted mean scores were 56.6 for Zylet, 46.4 for Lotemax and 48.4 for lubricant drops. The unadjusted recalculated comparisons had confidence intervals that included zero.

The registry record does not report secondary outcome results, a detailed analysis plan, missing-data methods, or the original sample-size justification. Serious adverse events and deaths were listed as 0 in each group, with other adverse events affected listed as 2, 1 and 2, respectively.