Punctal Plug Study to Determine the Safety and Retention Times of Various Lengths of Canalicular Stents in Volunteers: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Punctal Plug Study to Determine the Safety and Retention Times of Various Lengths of Canalicular Stents in Volunteers (NCT00743249), a randomized na study. The primary outcome is Mean Retention Time.

2. Clinical Question

The study was designed to examine safety and retention time for the two stent lengths in volunteers, including people with or without dry eye. Its primary outcome was a continuous measure: the mean number of days that the stent was retained during the stated follow-up period. A secondary outcome was the percentage of subjects retaining the stent at Month 3. These outcomes describe retention over follow-up and retention status at a specified visit, respectively; they are related but not interchangeable.

The posted results give the mean retention time as 87.4 days for the 10 mm arm and 61.9 days for the 20 mm arm. The unadjusted recalculation of the difference, defined as 20 mm minus 10 mm, is -25.5 days, with a 95% confidence interval from -40.01 to -10.99 days. The registry record does not report a sponsor analysis for this comparison. These figures describe the posted summaries and their estimated contrast, not a general conclusion about every patient or setting.

3. Trial Design

The registry identifies this as a randomized, parallel-group study with no masking. It lists the phase as NA and the status as completed. Enrollment is recorded as 60. The study start is listed as 2008-10, and primary completion is listed as 2009-02. Alcon Research is named as the sponsor. The registry record does not report further details of the randomization procedure, such as how the allocation sequence was generated or concealed.

Participants were assigned to a 10 mm or 20 mm MINI MONOKA canalicular stent. In each arm, the device was inserted in the lower lacrimal canaliculus of one eye for up to 3 months. The brief study description states that participants could have dry eye or not. The registry names healthy status and dry eye among the conditions. It does not report how these characteristics were distributed across arms, or whether assignment was stratified by them.

Masking is listed as none. The record therefore does not describe a masked design, but it does not give further information about the knowledge of participants, investigators, or outcome assessors regarding assigned stent length. The primary outcome was assessed by investigators through slit lamp examinations at study visits to establish whether a stent was present. The visit schedule beyond the stated interval is not reported in the registry record.

The primary endpoint population is listed as intent to treat. The outcome summaries show 28 participants in the 10 mm arm and 29 in the 20 mm arm, while the safety summaries list 30 at risk in each arm. These are the denominators recorded for the respective summaries; the registry record does not explain the difference between them. It also does not report a flow of participants through follow-up, reasons for missing outcome data, or the handling of withdrawals.

The record lists two outcome measures and one posted secondary outcome. It does not report a statistical analysis plan, a sample-size justification for the original trial, or the procedures used to analyze the original data. The planning figures associated with the posted summaries are illustrative calculations based on the observed effect, rather than the documented basis for the completed study's enrollment.

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:

Analysis population for the primary outcome, as defined in the registry: Intent to treat

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: This reporting group includes all randomized participants for whom stent insertion was successfully completed (57).

6. Primary Endpoint

The registry lists the primary outcome as Mean Retention Time, measured over From baseline (Day 0) up to Month 3.

The primary endpoint is mean retention time in days, measured from baseline (Day 0) up to Month 3. The registry describes an investigator using slit lamp examination at study visits to determine whether the canalicular stent was present. The endpoint therefore summarizes how long stents were retained over the stated follow-up interval. The record does not explain the precise calculation used to derive an individual retention time when a stent was not observed at a visit.

A mean is a measure of the central value of a continuous outcome. Comparing arm means provides a concise way to describe the average retention time in each randomized group. The accompanying standard deviation describes the spread of individual observations around the mean; it is not the uncertainty interval for the arm mean or for the difference between arms.

Retention time is relevant to the stated study purpose because the trial sought to assess how long stents remained in place. It differs from the secondary outcome, which records whether a subject retained the stent at Month 3. A time-based average can reflect variation across the follow-up period, while a status at a particular visit gives a yes-or-no result at that time. Interpretation of either measure depends on how visits, missing observations, and retention time were defined. Those details are not reported in the registry record.

7. Results Posted in the Registry

• Canalicular Stent, 20 mm: mean 61.90 versus 87.40 on control; difference -25.50 (95% CI -40.01 to -10.99), standardized effect d = -0.90; z-test p = <0.001.

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.

Percentage of Subjects Retaining the Stent at Month 3

• Endpoint type: Binary: the percentage of participants with the event (counts rebuilt from the posted percentages and group sizes).
• Test: Unadjusted two-proportion z-test, with a Wald 95% confidence interval for the risk difference.
• Result:
  • Canalicular Stent, 20 mm: 48.3% (14/29) versus 92.9% (26/28) on control; risk difference -44.6 percentage points (95% CI -65.1 to -24.0), risk ratio 0.52 (0.35–0.77); unadjusted two-proportion z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the proportion with the event is statistically lower for Canalicular Stent, 20 mm than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The registry record lists one posted secondary outcome: the percentage of subjects retaining the stent at Month 3. Its overall direction is consistent with the primary retention-time summaries: the posted percentage is higher in the 10 mm arm than in the 20 mm arm. This pattern offers a status-at-visit perspective alongside the primary measure of mean retention time across follow-up, but it does not make the outcomes equivalent.

The secondary comparison has an unadjusted recalculated p-value of <0.001. The registry record lists no reported analysis for this outcome. The result should therefore be read as a summary-statistic recalculation, not as a documented sponsor-reported analysis. The reported analyses field is empty, and the registry record does not describe an analysis plan for the secondary endpoint.

Unadjusted secondary results generally carry less weight than a prespecified primary result because multiple outcomes or comparisons can increase the chance of finding an apparently noteworthy result by chance. This is a general statistical concern, not a claim that a particular adjustment was required or performed in this trial. The registry record does not report a multiplicity strategy, a hierarchy for interpreting outcomes, or whether the secondary analysis was prespecified.

The secondary result can add context to the primary endpoint by asking whether the arms also differed in retention status at Month 3. It cannot establish that the primary finding is unbiased, explain why retention differed, or answer questions not measured by the study. The outcome's interpretation also depends on the definition and availability of Month 3 status, details that are not reported in the registry record.

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

• Percentage of Subjects Retaining the Stent at Month 3

9. Statistical Interpretation

10. Statistical Methods Explained

The primary outcome is continuous, and the posted arm summaries consist of a mean, standard deviation, and sample size for each stent length. A mean gives the arithmetic average on the outcome scale. Here that scale is days of retention. A standard deviation describes variation among observations in an arm. A larger standard deviation indicates more spread in the observed values, but it does not alone show whether an estimate is precise or whether a difference is important.

What does the mean difference express?

The contrast is defined as the 20 mm arm mean minus the 10 mm arm mean. A negative estimate therefore means the posted average is lower for the 20 mm arm. The recalculated estimate is -25.5 days. Its units remain days, which makes the contrast directly interpretable on the outcome scale. The estimate is not an adjusted effect: it uses the posted arm summaries without accounting for additional participant characteristics or other covariates.

What does a confidence interval add?

A confidence interval describes the statistical uncertainty around an estimate under the method's assumptions. For the mean difference, the 95% interval extends from -40.01 to -10.99 days. It is an interval for the contrast, not a range containing 95% of individual retention times. The interval gives a set of values compatible with the data and calculation method; it does not account for every possible source of uncertainty, such as measurement limitations or missing outcomes.

In general, a confidence interval is useful because it presents both the direction and precision of an estimated contrast. An interval concentrated around a narrow range indicates more precision than a broad interval. Whether a range is clinically important cannot be decided from statistical precision alone. The registry record does not state a threshold for a meaningful difference in retention time.

How should the p-value be read?

The unadjusted p-value for the recalculated primary comparison is <0.001. In general, a p-value is calculated under a null hypothesis and describes the compatibility of the data with that hypothesis, given the chosen statistical procedure. It is not a measure of effect size, does not give the probability that a result is false, and does not establish that a finding is clinically important. Since the registry record lists no reported analyses, the p-value should be understood as belonging to the unadjusted recalculation from the posted summaries, not as a documented sponsor-reported test.

In general, a comparison of means can use information about the sample sizes and variability in both arms to estimate uncertainty. The posted arm standard deviations are 16.8 days and 36.0 days. The larger spread in the 20 mm arm means its observed retention times were more variable around that arm's mean. The record does not identify the sponsor's analysis method, its assumptions, or whether any adjusted model was used. The recalculated comparison is therefore a simple, unadjusted summary-statistic comparison, not evidence of the trial's complete analytic approach.

Why distinguish the primary and secondary measures?

The primary measure summarizes mean retention time over the follow-up interval. The secondary measure reports the percentage of subjects retaining the stent at Month 3. A mean uses the measured time scale; a percentage summarizes a binary status at a specified visit. General statistical reasoning treats these as related but distinct outcomes: they can support a coherent overall pattern while answering different questions. A single endpoint does not reveal every feature of the other, and different endpoint definitions can lead to different uncertainty and analysis considerations.

The secondary outcome's posted arm percentages are 92.9% and 48.3%, with an unadjusted recalculated p-value of <0.001. The record gives participant counts retaining the stent as 26 and 14, respectively, among outcome denominators of 28 and 29. These descriptive figures should not be confused with a time-to-event analysis. The registry record does not report a time-to-event model or the handling of observations whose status was not available at the Month 3 assessment.

What can variability and over-dispersion mean?

In general, over-dispersion refers to greater variation in data than a chosen statistical model expects. It matters because a model that understates variability can produce uncertainty estimates that are too narrow and p-values that are too small. The primary endpoint is continuous, and the record does not report that an over-dispersion model was used or was needed. The difference between the two posted standard deviations alone does not establish over-dispersion. It does, however, make it important not to assume that the arms had identical variability when interpreting the summaries.

The mean comparison does not describe the full distribution of retention times. Two arms can have different spreads even when their means are the focus of the analysis. The record does not provide medians, quantiles, individual observations, or a distributional plot for this endpoint. No distributional assumption or diagnostic result is reported in the registry record, so these cannot be assessed from the posted summaries alone.

What is the status of these calculations?

The comparison values are unadjusted recalculations from posted summary statistics. The discrepancy flag is false, but the registry record still lists no reported primary analyses and no reported analyses for the secondary outcome. A recalculation is useful for describing the contrast and its statistical precision, while remaining distinct from an analysis documented by the study sponsor. It cannot establish how the original analysis was specified, whether there were prespecified covariates, or how departures from the intended data collection were handled.

11. Confidence Intervals and Precision

The primary mean difference is -25.5 days, with a 95% confidence interval from -40.01 to -10.99 days. The interval is entirely below zero, indicating that the unadjusted recalculation estimates a lower mean retention time in the 20 mm arm than in the 10 mm arm. Its endpoints also show that the precise magnitude is uncertain; the point estimate should not be read as an exact, universally applicable difference.

A confidence interval concerns uncertainty in the estimated arm contrast. It is not a prediction interval for an individual participant's retention time and does not describe the spread of observations within either arm. The arm standard deviations, 16.8 days for the 10 mm arm and 36.0 days for the 20 mm arm, describe within-arm variability. Those values and the confidence interval answer different statistical questions.

Precision depends on the amount and variability of the available outcome information, as well as the method used to estimate uncertainty. The outcome summaries include 28 participants in the 10 mm arm and 29 in the 20 mm arm. The registry record does not explain how missing observations, if any, affected the outcome denominators, or give a detailed method for the confidence interval. The interval therefore conveys precision under the recalculation, not assurance against bias or incomplete data.

The secondary outcome is also reported with an unadjusted comparison, but its estimates should be interpreted as a separate binary-outcome analysis. Statistical significance does not make an estimate precise in every relevant sense, and a narrow or directional interval cannot resolve limitations in outcome ascertainment. The registry record does not report a sponsor analysis or an adjustment for multiple comparisons. Confidence intervals and p-values should be read as statistical summaries of the posted results, rather than as guarantees about future observations.

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 calculation is described as an illustration based on the observed effect, with two-sided significance level 0.05, equal allocation between the two arms, and a normal approximation. The target effect is a stated fraction of the observed effect. The original trial's own design assumptions and sample-size justification are not reported in the registry record.

For the primary mean outcome, planning for 100% of the observed effect gives 20 participants per arm for 80% power and 26 participants per arm for 90% power. Planning for 75% of the observed effect gives 35 participants per arm for 80% power and 46 participants per arm for 90% power. Planning for 50% of the observed effect gives 78 participants per arm for 80% power and 104 participants per arm for 90% power.

For the Month 3 retention outcome, planning for 100% of the observed effect gives 16 participants per arm for 80% power and 20 participants per arm for 90% power. Planning for 75% of the observed effect gives 25 participants per arm for 80% power and 33 participants per arm for 90% power. Planning for 50% of the observed effect gives 47 participants per arm for 80% power and 62 participants per arm for 90% power.

In plain language, the 80% power column describes a planned sample size at which the stated calculation would have an 80% chance of detecting the chosen effect, under its assumptions. The 90% column uses a higher target chance of detection. Smaller effects are harder to detect and therefore require more participants per arm in these planning illustrations. These values are not observed power: they are hypothetical planning calculations based on the posted effect sizes, not a measure of the probability that the completed study's result is correct.

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 = -25.500; pooled standard deviation σ = 28.255.
2. n = 2 × (1.96 + 0.842)² × 28.255² / -25.500² = 19.3, rounded up to 20 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 <- -25.5                      # observed difference in means
sigma <- 28.254840293302                     # 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(743249)
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 = 20 (80% power), 26 (90% power)
 75% of observed effect: n per arm = 35 (80% power), 46 (90% power)
 50% of observed effect: n per arm = 78 (80% power), 104 (90% power)
power.t.test: 20.3 
Simulated power at n = 20 per arm: 0.795 (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 record identifies a primary endpoint and one posted secondary outcome, but it does not report a statistical analysis plan or a multiplicity procedure. Multiplicity arises when several outcomes, comparisons, or analyses are examined: even when no real effects exist, looking across many tests can make at least one apparently small p-value more likely. In general, adjustment procedures or a prespecified testing hierarchy can address this concern. The record does not establish whether such procedures were used in the original study.

The unadjusted recalculations should therefore be interpreted as individual comparisons. Their p-values do not account for any other outcomes or analyses, and the record does not say whether the primary and secondary outcomes were tested in a planned sequence. The absence of a reported strategy is a limitation in interpreting the role of the secondary finding; it is not evidence that the study did or did not conduct additional analyses.

The primary population is specified as intent to treat, but the registry record does not define how that population was implemented for the reported summaries. In general, an intent-to-treat approach aims to retain participants in their randomized groups for analysis. The record does not describe departures from assignment, exclusions, missing outcome observations, or imputation. It also does not report whether the secondary endpoint used the same analysis population as the primary endpoint.

The primary outcome summaries use 28 participants in the 10 mm arm and 29 in the 20 mm arm. Safety summaries list 30 participants at risk in each arm. The record does not explain these differing denominators, so they should not be reconciled by assumption. It also does not report the number or reasons for withdrawals, the timing of any missing observations, or how a participant without a recorded Month 3 status was treated.

For a retention-time endpoint, missing observations may affect the estimated mean depending on how the time of loss or absence was recorded and analyzed. The registry record does not report censoring rules or other methods for incomplete follow-up. These omissions limit the ability to assess whether the posted summaries reflect the intended analysis population and how robust the estimates are to missing data.

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 non-serious adverse event terms

The registry safety summaries list 30 participants at risk in each stent arm. For serious adverse events, 0 affected participants are recorded in each arm. The record lists no serious adverse-event terms. These figures describe the recorded counts in the registry; they do not establish that all possible harms were assessed or that no unrecorded events occurred.

For other adverse events, the registry records 5 affected participants in the 10 mm arm and 10 in the 20 mm arm, with 30 at risk in each arm. The record does not provide further event descriptions in the listed safety summary, and the number of deaths is null for both groups. A null death entry is not the same as a reported zero. The record does not give details on severity, timing, relatedness to the device, or event-specific follow-up.

Adverse-event counts are descriptive safety information. They do not by themselves show that the device caused an event or explain differences between arms. The record does not report a statistical comparison of adverse events, and small or short studies may not characterize uncommon or delayed events fully. These data should be read as the safety figures recorded for this study, with the reporting limitations in mind.

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

The posted results show a difference in mean retention time between the randomized stent-length arms over follow-up through Month 3. The 10 mm arm has a higher posted mean than the 20 mm arm, and the unadjusted recalculated mean difference has a confidence interval below zero. The Month 3 retention summaries point in the same direction. Together, these results describe the observed pattern in the registry record.

They do not establish why the arms differed. The study compares device lengths, but the registry record does not provide information about mechanisms or detailed analyses that could explain the result. The outcomes do not show whether a particular participant will retain a stent for a given time, nor do group averages predict an individual course.

The study's stated population is volunteers with or without dry eye, and the primary analysis population is listed as intent to treat. The record does not report enough eligibility and subgroup information to determine how results vary by dry-eye status or other characteristics. Generalization to populations beyond those described should therefore be cautious. Follow-up was limited to up to 3 months, so the posted outcomes do not characterize retention or safety beyond that interval.

Statistical evidence is not the same as clinical importance. The record does not specify a threshold for a meaningful difference in retention time, and a p-value does not supply one. Nor do these results establish a broad conclusion about safety: the registry lists adverse-event counts but lacks details about event types, attribution, and longer-term follow-up.

The comparisons are unadjusted recalculations from posted summaries, and the registry record lists no reported analyses. They support a statistical description of the available summaries, not a complete account of the original analysis or every source of uncertainty. The results should be understood within the study's design, population, outcome definitions, and follow-up rather than treated as a universal conclusion.

17. Why This Trial Matters Statistically

This trial illustrates why the endpoint definition matters. Mean retention time and retention status at Month 3 both concern whether a stent remains in place, but one summarizes time across follow-up while the other describes status at a visit. Their agreement in direction strengthens the descriptive coherence of the posted pattern, while their distinct definitions mean they should not be conflated.

The study also highlights the value of reporting variability alongside averages. The posted standard deviations differ between the arms, so the mean difference alone does not capture the spread of observed retention times. Confidence intervals add information about uncertainty in the contrast, but they do not resolve missing-data questions, possible measurement issues, or limitations in the study population.

Random allocation and a parallel-group comparison provide a framework for comparing stent lengths, while the lack of masking and limited registry detail are relevant when judging the evidence. The registry identifies slit lamp examination as the means of checking stent presence, yet does not report further procedures for outcome assessment or incomplete follow-up. Such details help readers distinguish a numerical result from the assumptions needed to interpret it.

Finally, the record makes a useful distinction possible between completed-study results and planning illustrations. The sample-size calculations use fractions of the observed effect and specified assumptions; they are not the documented original design rationale. Keeping planning calculations separate from evidence about the completed trial prevents hypothetical power targets from being mistaken for proof of precision or reliability.

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 record provides limited detail about the methods behind the posted outcomes. It does not report the randomization sequence or concealment, a full analysis plan, a justification for the original sample size, or sponsor-reported analyses. The comparison values are unadjusted recalculations from arm summaries, so potential adjustment choices made in the original study cannot be assessed.

The primary outcome is based on slit lamp examinations at study visits, but the visit schedule and the detailed derivation of retention time are not reported. The record does not say how an absent stent between visits was dated, how incomplete follow-up was handled, or how missing Month 3 status was treated. These details matter for understanding the construction of both endpoints.

The registry lists healthy status and dry eye among the conditions and describes volunteers with or without dry eye, but does not provide the distribution of these characteristics by arm or results within subgroups. The record also does not give detailed eligibility criteria. The applicability of the results outside the described volunteer population cannot be established from these summaries alone.

Outcome denominators and safety denominators differ: the outcome summaries list 28 participants in the 10 mm arm and 29 in the 20 mm arm, while the safety record lists 30 at risk in each arm. The reason is not reported in the registry record. It also does not provide participant flow, withdrawal reasons, adverse-event descriptions, or details of event severity and relatedness.

Follow-up was up to 3 months, limiting conclusions to the reported period. The record does not report a multiplicity strategy, a meaningful-difference threshold, or long-term retention and safety results. These are limits on interpretation, not evidence that the study's procedures or outcomes were necessarily inadequate.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: Punctal Plug Study to Determine the Safety and Retention Times of Various Lengths of Canalicular Stents in Volunteers — NCT00743249.
• Registry record last updated 2013-04-04; status last verified 2013-04.
• Results first posted 2013-04-04.
• 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

NCT00743249 is a completed randomized, parallel-group study with no masking, sponsored by Alcon Research. It compared 10 mm and 20 mm MINI MONOKA canalicular stents inserted in the lower lacrimal canaliculus of one eye for up to 3 months in volunteers with or without dry eye. Enrollment is listed as 60.

The primary endpoint was mean retention time in days from baseline (Day 0) up to Month 3, assessed through slit lamp examinations at study visits. Posted means were 87.4 days for the 10 mm arm and 61.9 days for the 20 mm arm. The unadjusted recalculated difference was -25.5 days, with a 95% confidence interval from -40.01 to -10.99 and p <0.001.

The secondary outcome was the percentage retaining the stent at Month 3. The registry also records serious and other adverse-event counts. It does not report sponsor analyses, a detailed analysis plan, the original sample-size rationale, or methods for missing data.