Effects of Carboxymethylcellulose Artificial Tears on the Eye Microbiome: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Carboxymethylcellulose Artificial Tears on the Eye Microbiome (NCT05292755), a randomized phase 4 study. The primary outcome is Species Richness.

2. Clinical Question

3. Trial Design

This completed phase 4 study is registered as randomized, double-blind, and parallel-group. The University of Florida is listed as sponsor. The record gives a start date of 2022-04-22 and a primary completion date of 2022-05-30. It lists enrollment as 80. The record does not report the method used to generate the random sequence, how treatment assignments were concealed, or which people were masked.

Participants in the experimental group used Refresh artificial tears containing 0.5% CMC, while participants in the control group used preservative-free, CMC-free Systane artificial tears containing 0.4% polyethylene glycol 400 and 0.3% propylene glycol. Both regimens were self-administered three times a day in each eye for 1 week. Because the products differ in more than the presence of CMC, the registry describes a comparison of these specific regimens.

The study description says surveys and conjunctival swabs were collected before and after treatment. The primary outcome was species richness assessed at day 1 and day 7, with day 7 reported. The registry also lists Ocular Surface Disease Index Score and Artificial Tear Use as secondary outcomes. Numerical results are posted for Artificial Tear Use; numerical Ocular Surface Disease Index results are not reported in the registry record.

The primary outcome summaries report 35 participants for the CMC group and 31 for the control group. These are outcome-specific group counts, not an explanation of who was randomized, excluded, or omitted from analysis. The registry record does not report an analysis population definition, participant flow, reasons for missing outcome data, or whether the analyses followed assigned treatment regardless of use.

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 Species Richness, measured over Assessed at day 1 and day 7, day 7 reported..

The primary endpoint is species richness at day 7, summarized as a mean and standard deviation for each treatment group. The registry describes how sampled 16S rRNA sequences were organized into operational taxonomic units at a 97% sequence similarity threshold. A phylogenetic tree was constructed from those units using the QIIME2 bioinformatics platform, and Faith's phylogenetic diversity was calculated with the QIIME2 faith pd plugin.

As a general explanation, Faith's phylogenetic diversity incorporates the lengths of branches represented in a sample's phylogenetic tree. In the registry's description, the measure is the sum of those branch lengths, expressed as nucleotide substitutions, or phylogenetic distance, per branch. Its scale runs from zero to infinity: zero indicates a completely homogenous sample, while higher scores indicate greater species richness.

This endpoint gives a quantitative way to compare the sampled eye microbiome across groups at the reported follow-up. It is a measure of richness based on the sequencing and bioinformatics approach described in the record; it is not itself a direct measure of symptoms or of clinical benefit. The record does not report additional details about laboratory quality control, sequence processing beyond the stated approach, or how the endpoint was handled when a sample was unavailable.

7. Results Posted in the Registry

• Preservative-free, CMC-free Artificial Tears: mean 11.10 versus 11.00 on control; difference 0.10 (95% CI -1.25 to 1.45), standardized effect d = 0.04; z-test p = 0.885.

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.

Artificial Tear Use

• 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:
  • Preservative-free, CMC-free Artificial Tears: mean 2.16 versus 2.86 on control; difference -0.70 (95% CI -1.09 to -0.31), standardized effect d = -0.86; z-test p = <0.001.
• Interpretation:
  • The 95% confidence interval excludes no difference, so the mean is statistically lower for Preservative-free, CMC-free Artificial Tears than for the control. This is an unadjusted, secondary comparison, so it is suggestive rather than confirmatory.

The registry lists Ocular Surface Disease Index Score and Artificial Tear Use as secondary outcomes. Numerical results are posted for Artificial Tear Use, while numerical Ocular Surface Disease Index results are not reported in the registry record. The available secondary evidence is therefore incomplete and should not be read as a full account of all listed secondary outcomes.

The reported Artificial Tear Use summaries show group means of 2.86 and 2.16 eyedrops per day at day 7, with standard deviations of 0.81 and 0.82. The unadjusted mean difference, comparing control with CMC, is -0.7, with a 95% confidence interval from -1.094 to -0.306 and p<0.001. These are descriptive and inferential results for a secondary measure, not a second estimate of the primary microbiome endpoint.

As a general explanation, secondary outcomes can add context by describing other measures collected in a trial, but they do not replace the prespecified primary question. A secondary outcome's statistical result does not establish the primary result, and a pattern across outcomes should be interpreted in light of how many measures and analyses were considered. The registry lists 6 outcome measures and 3 analyses, but does not report a multiplicity adjustment or a hierarchy among secondary tests.

Unadjusted secondary p-values carry less weight when many outcomes or analyses may be examined because the chance of at least one apparently notable result can increase across repeated testing. This is a general statistical concern, not evidence that any particular result is false. The record does not report enough information to determine which analyses were planned in advance, how missing secondary measurements were handled, or whether any adjustment was performed outside the posted information.

Overall, the reported secondary information does not resolve the uncertainty around the primary species-richness comparison. It offers a separate observation about reported drop use, while the other listed secondary outcome lacks numerical results in the registry record. The results should remain distinct rather than being combined into a single claim about the study.

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

• Ocular Surface Disease Index Score
• Artificial Tear Use

9. Statistical Interpretation

10. Statistical Methods Explained

The registry identifies the primary outcome as a continuous measure summarized by means and standard deviations. It also reports an ANOVA analysis and supports a simple unadjusted comparison of the posted group means. These approaches answer related but not necessarily identical statistical questions, and the registry does not provide enough analysis detail to reconcile them fully.

What does a mean difference describe?

As a general explanation, a mean difference subtracts one group's average from the other group's average. The recalculation uses the control mean of 11.1 and the CMC mean of 11.0, so the stated direction is control minus CMC. The estimated difference is 0.1. The sign indicates which group has the higher sample mean under that subtraction convention; it does not, by itself, establish that the difference is meaningful or caused by treatment.

A mean difference is expressed in the outcome's own units. Here, the registry describes the outcome as phylogenetic distance based on branch lengths, and labels the unit as units on a scale. The result should not be interpreted as a percentage change or as a count of organisms. The record does not report a transformation of the outcome or an adjusted mean difference.

What does the confidence interval add?

As a general explanation, a confidence interval represents a range of values compatible with the data under the statistical procedure used. The recalculated 95% confidence interval for the primary mean difference runs from -1.254 to 1.454. It includes zero, the value corresponding to no difference in group means under this contrast. Its inclusion of zero is consistent with the recalculated p-value of 0.885, but the interval communicates more than a threshold-based decision: it shows the range of effects that remain compatible with the posted summaries and calculation.

The interval is based on an unadjusted calculation from the posted summary statistics, not on the sponsor's ANOVA. The registry does not report a confidence interval for the ANOVA result. As a general point, confidence intervals rely on assumptions about the sampling process and the calculation method; the registry does not report diagnostic checks or enough information to evaluate all those assumptions.

What does ANOVA test?

As a general explanation, analysis of variance compares group means relative to the variation within groups. In a comparison of two groups, it is a method for testing whether the observed means are consistent with a common mean under the model. The registry reports ANOVA and p=0.232 for the primary outcome. It does not state whether this analysis was adjusted for baseline measurements, other covariates, or any other factors, nor does it provide the model details or an effect estimate from that analysis.

The recalculated unadjusted p-value of 0.885 comes from the posted group summaries and is not the same as the sponsor's ANOVA p-value. A p-value measures how unusual data at least as discrepant as those observed would be under a specified null model and its assumptions. It is not the probability that the null hypothesis is true, and it does not measure the magnitude or practical importance of an effect.

Why can variability matter?

As a general explanation, standard deviations describe the spread of individual observations around a group mean. The primary outcome standard deviations are 2.1 for the CMC group and 3.3 for the control group. More variability can make a group mean less precisely estimated when other aspects of a study are similar. The difference in the reported standard deviations also means that a simple common-variance description should not be assumed without checking the chosen method's assumptions.

Over-dispersion is a general concern when observed variability is larger than a statistical model expects. If it is not addressed, standard errors and uncertainty estimates can be misleading. The primary outcome is continuous, and the registry does not report that over-dispersion was identified or that a specific correction was used. The more general lesson is that the outcome distribution, spread, and modeling assumptions should be considered when interpreting a mean comparison.

How should the result be understood with the design?

Randomization can help make assigned groups comparable on average, but it does not guarantee balance in every realized sample. Masking can reduce some forms of bias, but the registry does not identify who was masked or how masking was maintained. The record also does not describe the analysis population, missing-data handling, or any baseline adjustment. These omissions limit what can be inferred about the exact estimand and the robustness of the reported analysis.

The primary endpoint was assessed at day 1 and day 7, with day 7 reported. A baseline measure could be useful in analysis, but the registry does not say whether the day 1 result was used to adjust the day 7 comparison. The posted recalculation uses the reported day 7 group means and standard deviations only. It should therefore be distinguished from any model that may have used additional information.

11. Confidence Intervals and Precision

The recalculated primary mean difference is 0.1, with a 95% confidence interval from -1.254 to 1.454. This interval is centered around a small estimated difference, but its endpoints span values on both sides of zero. Thus, the posted summary data do not tightly locate the difference in means. The interval is the most direct way to see the uncertainty around the recalculated estimate.

As a general explanation, a confidence interval is not a range that contains a fixed proportion of individual participants' observations. It describes uncertainty about a population quantity under the calculation's assumptions. It also does not mean that every value in the interval is equally plausible, or that values outside it are impossible. The width reflects both the observed variability and the amount of information available for the calculation.

The outcome summaries report standard deviations of 2.1 in the CMC group and 3.3 in the control group. The posted group sizes for this outcome are 35 and 31. Those values are relevant context for the recalculated precision, but the interval remains an unadjusted estimate derived from the summaries. It is not an interval reported for the sponsor's ANOVA.

The ANOVA p-value is 0.232, but no corresponding estimate or confidence interval is reported in the registry record. A p-value alone does not show the size or precision of an effect. The recalculated interval should therefore be interpreted as describing the unadjusted mean difference, not as a confidence interval for the sponsor's analysis.

The registry does not report a prespecified equivalence margin, a minimum important difference, or an interval-based decision rule. Consequently, the interval cannot be used to declare equivalence. It instead indicates that the observed summaries are compatible with a range of possible mean differences, and that the available result does not pin down the magnitude with high precision.

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 sample-size figures are planning illustrations based on the observed effect, not the trial's original design assumptions. The original design assumptions are not reported in the registry record. These planning calculations use a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each planning row uses the stated fraction of the observed effect as the effect to detect.

The figures are participants per arm, rather than total participants or total events. For the primary outcome, planning for 100% of the observed effect gives 11,691 participants per arm for 80% power and 15,651 participants per arm for 90% power. Planning for 75% of the observed effect gives 20,784 participants per arm for 80% power and 27,824 participants per arm for 90% power. Planning for 50% of the observed effect gives 46,764 participants per arm for 80% power and 62,604 participants per arm for 90% power.

As a general explanation, power is the chance that a study using a specified design and analysis will detect an effect of a specified size under the assumptions used for planning. The 80% and 90% columns describe different target chances of detecting that effect, not probabilities that the observed result is true. The higher target requires more participants in these illustrations. Smaller effects also require more participants to detect, because they are harder to distinguish from variation in the outcome.

These calculations are planning illustrations, not observed power. They do not say how much power the completed trial had after seeing its results, and they should not be used to infer why the original enrollment was selected. The registry record does not report the trial's original sample-size justification or design assumptions.

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 = 0.100; pooled standard deviation σ = 2.729.
2. n = 2 × (1.96 + 0.842)² × 2.729² / 0.100² = 11,690.9, rounded up to 11,691 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 <- 0.0999999999999996                      # observed difference in means
sigma <- 2.72901080979904                     # 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(5292755)
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 = 11,691 (80% power), 15,651 (90% power)
 75% of observed effect: n per arm = 20,784 (80% power), 27,824 (90% power)
 50% of observed effect: n per arm = 46,764 (80% power), 62,604 (90% power)
power.t.test: 11691.9 
Simulated power at n = 11,691 per arm: 0.801 (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. Analyses Reported by the Sponsor

The registry reports the sponsor's primary analysis as ANOVA with p=0.232. It does not report an effect estimate, confidence interval, or model specification for that analysis. Separately, the unadjusted recalculation from the posted day 7 means and standard deviations gives a control-minus-CMC mean difference of 0.1, a 95% confidence interval from -1.254 to 1.454, and p=0.885.

These figures should not be presented as though they came from one identical analysis. The recalculation is a simple comparison of the posted summary statistics; the ANOVA may reflect a different procedure, but its details are not reported. The registry's discrepancy indicator is false, yet the distinct p-values still warrant transparent reporting and careful distinction.

The sponsor's result is the registry's reported analysis, while the recalculation is an additional unadjusted reading of the summaries. The record does not provide enough detail to determine why the p-values differ or which assumptions each analysis used. No claim about an analysis taking precedence is indicated by the reported discrepancy status.

15. Multiplicity, Missing Data and Analysis Populations

Multiplicity refers, as a general statistical concept, to the increased chance of obtaining at least one seemingly notable result when several outcomes, time points, groups, or analyses are tested. The registry lists 6 outcome measures and 3 analyses and names secondary outcomes that include Ocular Surface Disease Index Score and Artificial Tear Use. It does not report a multiplicity adjustment, a testing hierarchy, or which outcomes were designated as confirmatory beyond identifying the primary outcome.

Without those details, the reported p-values should be read as the results of the stated analyses, not automatically as family-wise error-controlled tests. The unadjusted secondary p-value in particular should be treated as exploratory context unless a prespecified analysis plan establishes otherwise. The registry record does not report such a plan or a correction method, so no adjustment should be assumed.

The record also does not report the analysis population definition. It provides outcome group sizes for the primary endpoint and Artificial Tear Use, but does not explain whether participants were analyzed according to randomized assignment, treatment received, or availability of an outcome measurement. Participant flow, exclusions, and reasons for missing data are not reported in the registry record.

Missingness can affect estimates when the availability of an outcome is related to the outcome itself or to group assignment. As a general explanation, complete-case summaries can differ from results that account for missing observations, depending on why data are missing and the method used. The record does not describe imputation, sensitivity analyses, or another missing-data strategy. It also does not state whether every participant who began the study contributed a day 7 swab and survey.

The primary outcome description includes assessment at day 1 and day 7, but only the day 7 result is reported. The record does not say whether day 1 results informed the analysis. It also does not report a protocol or statistical analysis plan that would clarify planned time points, covariate adjustment, outcome prioritization, or handling of departures from the intended regimen. These omissions limit assessment of selective reporting and analysis robustness.

16. 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.

The registry reports 40 participants at risk in each group for serious adverse events and zero serious adverse events in each. It also reports 40 participants at risk in each group for other adverse events and zero other adverse events in each. The record lists zero deaths in each group and no top serious adverse event terms.

These are the registry's posted adverse-event counts for the categories shown. They do not establish that no symptoms or other events occurred outside the registry's definitions or collection period. The record does not provide additional detail about how events were solicited, what time interval was used for safety collection, how severity or relatedness was assessed, or whether all participants completed safety follow-up.

As a general interpretation, zero reported events in these categories means that no events were recorded in the posted counts; it does not establish that the products have no risks. These figures should be read as registry reporting, not as a complete safety profile or a basis for individual treatment decisions.

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

The posted primary results describe similar observed day 7 group means for species richness: 11.0 for the CMC artificial tears group and 11.1 for the preservative-free, CMC-free group. The recalculated unadjusted difference is 0.1, and its 95% confidence interval includes zero and spans values in both directions. The sponsor reports an ANOVA p-value of 0.232. Together, these results do not provide a precise estimate of the group difference or establish a clear separation in the reported primary outcome.

That interpretation is not equivalent to proving that the groups are the same. The record does not report an equivalence margin or a clinically meaningful threshold for the richness measure. A confidence interval that includes zero is compatible with no difference, but it can also be compatible with nonzero differences. The width of the interval matters when considering what differences remain plausible.

The trial compares two particular artificial tear regimens: one containing 0.5% CMC and one described as preservative-free and CMC-free, with different listed ingredients. Accordingly, an observed group contrast would concern the assigned products as described. The record does not isolate the effect of CMC from all other product differences.

The endpoint is a sequencing-derived measure of phylogenetic diversity, not a direct measure of symptoms, quality of life, or longer-term eye health. The registry lists Ocular Surface Disease Index Score as a secondary outcome, but numerical results for that outcome are not reported in the registry record. The reported Artificial Tear Use result is a separate secondary measure and does not establish a microbiome effect.

The findings apply to the posted outcomes and follow-up described in this completed study. They do not establish effects beyond the reported 1-week regimen or at time points not reported. Missing-data handling, analysis populations, and several design and analysis details are not reported in the registry record, which limits assessment of how robustly the estimates reflect all enrolled participants.

18. Why This Trial Matters Statistically

This study raises a statistical question at the intersection of a product comparison and a biological measurement: whether a brief course of CMC-containing artificial tears is associated with a difference in a sequencing-derived measure of ocular microbiome richness. The registry specifies the laboratory-derived endpoint and the day 7 comparison, making the statistical target more concrete than a broad question about the microbiome.

The results also illustrate why estimates and uncertainty are more informative than a p-value alone. The recalculated mean difference is 0.1, while the confidence interval extends across zero and includes a range of possible values. The sponsor's reported ANOVA p-value and the unadjusted recalculated p-value differ, and the record does not provide enough methodological detail to reconcile them. Distinguishing analyses and reporting their limitations is important for a fair reading of trial evidence.

Another statistical issue is the relationship between a primary outcome and multiple secondary outcomes. The record identifies several outcome measures and analyses, but does not describe a multiplicity strategy or the analysis plan. This makes it important to avoid treating a secondary p-value as if it were independent confirmation of the primary result.

The trial also highlights the difference between an observed estimate and a planning target. The sample-size illustrations use fractions of the observed effect and specified planning assumptions, but the registry does not report the original design justification. Those illustrations can demonstrate how precision requirements change with target effect size; they do not explain the enrollment decision for the completed study.

Finally, the endpoint's technical definition matters. Faith's phylogenetic diversity reflects branch lengths in a constructed tree, so interpretation depends on the sequencing and bioinformatics approach as well as the statistical comparison. Clear reporting of the measurement, analysis population, missing data, and model would help readers assess what the estimate represents.

19. 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 arise from information not reported in the registry record. The record does not describe the randomization sequence, allocation concealment, masking procedures, or who remained masked. It therefore does not allow a detailed assessment of how assignment and masking were implemented.

The primary outcome summaries report 35 participants in the CMC group and 31 in the control group, while the enrollment is 80. The record does not explain the participant flow or the relationship between enrollment and the outcome-specific group counts. It does not report an analysis population definition, exclusions, missing day 7 measurements, or methods for handling missing data.

The sponsor's ANOVA is reported without an effect estimate, confidence interval, model specification, or explanation of its relation to baseline measurements. The unadjusted recalculation uses only the posted summary statistics. These presentations do not supply enough detail to determine whether the sponsor's model addressed other information or assumptions that could affect the result.

The record does not report a multiplicity plan, a hierarchy for secondary outcomes, or an analysis plan. Numerical results for Ocular Surface Disease Index Score are not reported in the registry record. The absence of these details limits assessment of selective reporting and the evidential weight of secondary findings.

The two artificial tear products differ in their listed ingredients as well as CMC status. The registry therefore describes a comparison between products, and the result cannot be attributed solely to the presence or absence of CMC based on this record. The primary result is reported at day 7 after a 1-week regimen; effects at other follow-up times are not reported. Finally, the registry does not report a threshold for a meaningful difference in species richness, making it difficult to judge practical importance from the numerical estimate alone.

20. Related Tutorials

21. Related Statistical Calculators

22. Sources

• ClinicalTrials.gov: Effects of Carboxymethylcellulose Artificial Tears on the Eye Microbiome — NCT05292755.
• Registry record last updated 2023-04-20; status last verified 2023-03.
• Results first posted 2023-04-20.
• 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.

23. Record Summary

The registry describes a completed randomized, double-blind, parallel phase 4 study of carboxymethylcellulose artificial tears versus preservative-free, CMC-free artificial tears in people with dry eye syndromes. The University of Florida is listed as sponsor, and enrollment is 80. Each regimen was self-administered three times a day in each eye for 1 week.

The primary outcome was day 7 species richness measured using Faith's phylogenetic diversity from sampled 16S rRNA sequences. The group means were 11.0 and 11.1. The unadjusted recalculated mean difference was 0.1, with a 95% confidence interval from -1.254 to 1.454 and p=0.885. The sponsor-reported ANOVA p-value was 0.232.

The registry also lists Ocular Surface Disease Index Score and Artificial Tear Use as secondary outcomes. Numerical results are posted for Artificial Tear Use, but not for Ocular Surface Disease Index Score. The record reports zero serious adverse events, other adverse events, and deaths in the posted group counts. Details about the original sample-size justification, multiplicity, missing data, and analysis populations are not reported in the registry record.