Multifocal Visual Performance Study: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Multifocal Visual Performance Study (NCT03757039), a randomized na study. The primary outcome is Average Transition Time, Calculated From a Maximum of 3 Readings, Recorded in Seconds, During Alternate Viewing From Distance (4 m) to Intermediate (80 cm) and Vice Versa (Full Analysis Set).

2. Clinical Question

The study asked whether visual transition time differed between people using multifocal soft contact lenses and people using progressive addition lens (PAL) spectacles. Participants had presbyopia, and testing assessed how quickly they shifted between reading text at distance and reading text at an intermediate viewing distance.

The endpoint focused on the interval between stopping one reading task and starting the other. It therefore describes a specific aspect of visual task transition under the study’s test conditions, rather than a broad measure of vision or everyday performance. The registry’s description says the endpoint was measured inconsistently, compromising interpretation, and that the planned inferential analysis was not carried out. The posted averages can be described, but the record does not support a planned statistical test of the arm comparison.

3. Trial Design

This was a randomized, double-masked, parallel-group study of multifocal contact lenses and PAL spectacles. The registry lists an enrollment of 42 and identifies presbyopia as the condition studied. The sponsor was Alcon Research. The study began on 2018-12-16, and primary completion was recorded on 2019-03-06. Its status is listed as terminated; the reason for termination is not reported in the registry record.

The contact lens arm used multifocal soft contact lenses selected according to each subject’s prescription and fitted using the Alcon multifocal fitting guide. The lenses were worn bilaterally for up to 3 hours on 1 day only. In the PAL arm, subjects used progressive addition lens spectacles according to their habitual prescription, with testing also lasting up to 3 hours on 1 day only. These descriptions indicate a short, single-day test; they do not establish how results would relate to longer-term use.

The primary outcome was a continuous measure: average transition time in seconds. The registry lists 32 participants for the multifocal contact lens arm and 9 for the PAL spectacles arm in the posted outcome results. The recorded arm summaries are means with standard deviations. The primary outcome description identifies the analysis population as the Full Analysis Set, defined as subjects assigned to PALs or randomized to the contact lens group who were exposed to any study product evaluated in the study, except lenses used for optimization and fitting.

The registry labels the study phase as not applicable. It lists one outcome measure, no posted secondary outcomes, and no analyses. Although the study was randomized and double-masked, the registry does not report details of the masking procedures or how allocation was generated or concealed. These design details 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.

Before assignment: Of the 42 enrolled, 1 subject was exited from the study as a screen failure prior to randomization. This reporting group includes all randomized/assigned subjects (41).

Overall Study

Analysis population for the primary outcome, as defined in the registry: This analysis population includes all subjects assigned to PALs or randomized to the contact lens group who were exposed to any study product evaluated in this study, except for the lenses used for optimization and fitting (Full Analysis Set).

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 analysis population includes all subjects exposed to any study product evaluated in this study, except for the lenses used at Visit 2 for the purpose of parameter optimization and fitting, as they are not intended for the assessment of safety (Safety Analysis Set).

6. Primary Endpoint

The registry lists the primary outcome as Average Transition Time, Calculated From a Maximum of 3 Readings, Recorded in Seconds, During Alternate Viewing From Distance (4 m) to Intermediate (80 cm) and Vice Versa (Full Analysis Set), measured over Day 1, after up to 3 hours of wear.

The primary endpoint was average transition time, recorded in seconds, during alternate viewing between distance text at 4 meters and intermediate text at 80 centimeters. A subject read text at one viewing distance and then immediately read text at the other. The time interval began when the subject stopped reading the first text and ended when the subject started reading the second. The outcome was calculated from a maximum of 3 readings on Day 1, after up to 3 hours of wear.

This measure captures the timing of a specific transition between two near-related visual tasks. A shorter transition interval, as defined by the endpoint, corresponds to less time between stopping the first reading task and starting the next. It does not by itself describe reading accuracy, comfort, sustained performance, or visual function in other settings; those are distinct outcomes.

The registry reports a mean and standard deviation for each arm. A mean describes the arm’s average observed transition time, while the standard deviation describes how spread out individual measurements were around that average. Neither statistic alone establishes whether an observed difference between arm averages is statistically distinguishable from random variation.

The registry explicitly notes inconsistent measurement of this primary endpoint. It states that interpretation of the average transition times was compromised and that the planned inferential analysis was not carried out. That limitation is central to reading the endpoint results: the posted summaries describe the recorded measurements, but the registry does not present a planned inferential comparison.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is continuous: each recorded transition time is expressed in seconds, and the registry summarizes the arm results using means and standard deviations. In general, a continuous outcome can be described by its central tendency and variability. The mean gives the arithmetic average of recorded observations; the standard deviation describes how dispersed those observations are around the mean. These summaries help characterize the observed data, but they do not by themselves quantify uncertainty in a comparison between groups.

What do the arm summaries say?

The multifocal contact lens arm has a reported mean of 2.602 seconds and standard deviation of 1.136, based on 32 participants. The PAL spectacles arm has a reported mean of 2.774 seconds and standard deviation of 0.839, based on 9 participants. Those figures are descriptive. They do not include an estimate of the between-arm contrast or a confidence interval for that contrast. No new comparison should be inferred from the arm summaries alone.

Why is there no inferential result?

The registry states that inconsistent measurement of the primary endpoint compromised interpretation of the average transition times and that the planned inferential analysis was not carried out. Inferential methods are generally used to assess how compatible observed data are with a range of possible effects, while accounting for sampling uncertainty and a specified analysis plan. Here, the registry does not post a planned test result, p-value, or confidence interval for the arm comparison. The stated measurement problem limits interpretation before any such comparison can be treated as informative.

In general, measurement consistency matters because a statistical procedure cannot correct an outcome that was recorded inconsistently. If the same underlying task is measured differently across observations, the resulting values may not be directly comparable. The registry does not describe the nature or extent of the inconsistencies, so their specific impact cannot be quantified from the record.

How should variability be understood?

A standard deviation is not a confidence interval and is not a direct measure of the precision of a treatment contrast. It describes variation among recorded observations within an arm. A confidence interval for an arm difference would address uncertainty about that comparison, using a specified method and assumptions. In general, confidence intervals are useful because they show both the estimated effect and the range of values that remain compatible with the data under the method used. No such interval is reported for this endpoint.

The sizes of the outcome groups are also relevant to precision: the posted results include 32 participants for multifocal contact lenses and 9 for PAL spectacles. In general, less information in an arm can make estimates less precise, but the registry does not report a precision calculation for these results. The observed standard deviations and group sizes should not be converted into a new inferential result when the registry states that the planned analysis was not carried out.

What can a planning calculation establish?

In general, sample-size calculations are planning tools that describe the number of participants needed under stated assumptions to detect a chosen effect with a specified error rate and power. They are not measures of the probability that a completed study has found a true effect. Any planning illustration based on an observed effect is especially dependent on that observed estimate and its context. The registry record does not report the trial’s own sample-size justification or a usable planning result for this two-arm endpoint comparison. The endpoint’s measurement problem also cautions against treating an observed effect as a dependable planning target.

“Observed power” is not a substitute for a confidence interval or a clear estimate of uncertainty. In general, a post hoc power calculation based on the observed effect largely restates information in the data and does not resolve whether measurement was consistent or whether the estimate is precise. No observed-power result is reported in the registry record.

What analysis details are absent?

The record identifies randomization, double masking, a parallel-group model, the outcome population, and the descriptive summary measure. It does not report the statistical model or test planned for the endpoint, a method for adjusting for baseline measurements, a missing-data method, or interim analyses. Those details are not reported in the registry record and should not be inferred from the design labels or the posted summaries.

In general, a prespecified analysis plan helps clarify which comparison is primary, how uncertainty is quantified, and how data issues are handled. When that plan is unavailable, interpretation should remain close to the reported summaries and documented limitations. For this outcome, the registry itself supplies an especially important qualification: inconsistent measurement compromised interpretation, and the planned inferential analysis was not carried out.

10. Confidence Intervals for Each Arm

No two-arm comparison is shown for this trial, but each arm's mean can be given with a t-based 95% confidence interval computed from the posted mean, spread and number of participants.

R code and output

arm <- c("Multifocal Contact Lenses", "PAL Spectacles")
n   <- c(32, 9)
m   <- c(2.602, 2.774)
sp  <- c(1.136, 0.839)
sd  <- sp      # posted standard deviations
for (i in seq_along(n)) {
  se <- sd[i] / sqrt(n[i]); h <- qt(0.975, n[i] - 1) * se
  cat(sprintf("CARM|%s|%d|%.3f|%.3f|%.3f|%.3f\n", arm[i], n[i], m[i], sd[i], m[i] - h, m[i] + h))
}

CARM  Multifocal Contact Lenses  32  2.602  1.136  2.192  3.012
CARM  PAL Spectacles  9  2.774  0.839  2.129  3.419

11. Multiplicity, Missing Data and Analysis Populations

The registry lists one outcome measure and no posted secondary outcomes. It also lists no analyses. The record does not report a multiplicity adjustment or explain how the analysis would have controlled the chance of false-positive findings across multiple outcomes or comparisons. Since no planned inferential result is posted for the primary endpoint, there is no reported family of inferential tests to evaluate for multiplicity.

The Full Analysis Set is defined as subjects assigned to PALs or randomized to the contact lens group who were exposed to any study product evaluated in the study, except lenses used for optimization and fitting. The primary outcome description uses this population definition. The registry does not report the number of participants included in that set separately from the posted arm counts or describe any additional analysis populations.

Missing-data handling is not reported in the registry record. The record does not state whether any endpoint observations were missing, how incomplete measurements were treated, or whether any participants were excluded from the endpoint summaries. It also does not report a sensitivity analysis assessing the effect of missing observations.

These omissions do not establish that data were missing or that the analysis was biased; they mean the registry record does not describe the relevant procedures or quantities. The explicitly reported inconsistency in endpoint measurement is a separate concern: it compromised interpretation and led to the planned inferential analysis not being carried out. Accordingly, the posted means and standard deviations should be read as descriptive summaries within the defined population, not as a complete account of a prespecified inferential analysis.

12. 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 5% reporting threshold.

Most frequent non-serious adverse event terms

The registry reports serious adverse event figures in separate safety groups. The AOHG MF group had 11 participants at risk and 0 serious adverse events; the DT1 MF group had 11 at risk and 0 serious adverse events; the DACP MF group had 10 at risk and 0 serious adverse events; and the PALs group had 9 at risk and 0 serious adverse events. The registry reports no deaths in these groups.

For other, non-serious adverse events, the AOHG MF, DT1 MF, and DACP MF groups each had 0 affected participants among 11, 11, and 10 at risk, respectively. The PALs group had 1 affected participant among 9 at risk. These are the event counts as reported for those safety groups; the registry does not provide a list of serious adverse event terms.

Safety figures are counts within the reported groups, not a comparison adjusted for exposure time or other factors. The at-risk counts in these safety groups should not be assumed to match the outcome-analysis populations or the arm counts reported for the primary endpoint. The record does not explain the relationship between the safety group labels and the outcome arms in further detail.

Zero reported serious adverse events in these groups means none were recorded in the registry’s listed figures. It does not by itself establish that an intervention is free of risk, particularly when the study was short and the registry does not provide further safety analysis details.

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

The registry’s outcome summaries describe average transition times recorded during a brief test of alternate distance and intermediate reading. The reported mean was 2.602 seconds for multifocal contact lenses and 2.774 seconds for PAL spectacles. The standard deviations were 1.136 and 0.839, respectively. The registry also states that measurement of the endpoint was inconsistent, compromising interpretation, and that the planned inferential analysis was not carried out.

As a result, the record does not establish whether the difference in the arm averages is statistically distinguishable from random variation, nor does it establish equivalence between the groups. No confidence interval or planned inferential result is reported for the comparison. The numerical ordering of the means is descriptive only and must be interpreted in light of the stated measurement limitation.

The result concerns a narrowly defined task: moving from reading at distance to reading at an intermediate distance, or the reverse, after up to 3 hours of wear on 1 day. It does not measure all aspects of visual performance, and the record does not report results for other visual outcomes. The posted result cannot establish how either product would perform over longer use or in settings not represented by this test.

The registry describes a randomized, double-masked, parallel-group study, but the record does not report details of allocation procedures, masking methods, or the planned statistical model. It also does not report missing-data methods or the trial’s sample-size justification. These gaps limit how fully the design and analysis can be appraised from the registry record.

The appropriate reading is therefore limited: the record contains descriptive arm summaries for the stated endpoint, together with a direct warning that inconsistent measurement undermined interpretation. It does not support a firm comparative conclusion about visual transition performance.

14. Why This Trial Matters Statistically

This study is statistically notable because its primary endpoint was a timing measure intended to summarize a specific visual task, yet the registry reports that the endpoint was measured inconsistently. That distinction matters: statistical summaries can describe recorded values, but the interpretability of those values depends on whether the underlying measurement was applied consistently. The registry’s decision not to carry out the planned inferential analysis reflects that limitation.

The record also illustrates the difference between descriptive and inferential results. Arm means and standard deviations can show the observed averages and within-arm spread. They do not, on their own, establish a comparative effect with quantified precision. Without a reported inferential analysis or confidence interval, the reader cannot assess the uncertainty around the between-arm comparison using the registry results.

The outcome population and safety groups are reported in different terms, and the registry does not explain their relationship in detail. This emphasizes the value of clearly describing who contributed to each analysis and how safety populations relate to efficacy populations. The record defines the Full Analysis Set for the primary endpoint, but it does not report missing-data handling or additional analysis populations.

Finally, the study’s short testing period and single-day wear conditions define the context for the endpoint. Statistical conclusions are always tied to the population, measurement, and conditions that generated the data. Here, the record supports a narrow descriptive account, while the inconsistent measurement and absent planned inferential result sharply limit comparative interpretation.

15. 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 identifies inconsistent measurement of the primary endpoint as a direct limitation: interpretation of the average transition times was compromised, and the planned inferential analysis was not carried out. It does not describe what was inconsistent, how many measurements were affected, or whether the issue differed between arms. The size and direction of any resulting measurement error are therefore not reported in the registry record.

The posted outcome groups contain 32 participants for multifocal contact lenses and 9 for PAL spectacles. The record does not explain the difference between the enrollment of 42 and the group counts shown for the outcome, or provide a participant-flow account. The reason for the terminated status is also not reported in the registry record.

The outcome was assessed on Day 1 after up to 3 hours of wear, with testing conducted for 1 day only. This limits the result to the brief conditions described and does not provide evidence about longer-term use. The primary endpoint captures timing between two reading tasks; the registry does not report other visual-performance measures or secondary outcome results.

Further analysis details are not reported in the registry record, including the planned statistical test or model, missing-data procedures, interim analyses, and the trial’s sample-size justification. No confidence interval or inferential result for the arm comparison is posted. These omissions mean the precision and robustness of a comparative estimate cannot be assessed from the registry summaries.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Multifocal Visual Performance Study — NCT03757039.
• Registry record last updated 2020-03-25; status last verified 2020-03.
• Results first posted 2020-03-25.
• 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.

19. Record Summary

NCT03757039, titled “Multifocal Visual Performance Study,” is a randomized, double-masked, parallel-group study sponsored by Alcon Research. It enrolled 42 participants with presbyopia and is listed as terminated. The recorded start date is 2018-12-16, and primary completion was 2019-03-06.

The study compared multifocal soft contact lenses with progressive addition lens spectacles. The primary endpoint was average time in seconds to transition between distance and intermediate reading on Day 1 after up to 3 hours of wear. The posted means were 2.602 seconds for the contact lens arm and 2.774 seconds for the PAL spectacles arm. The registry states that inconsistent endpoint measurement compromised interpretation and that the planned inferential analysis was not carried out.

The registry lists no secondary outcomes and no analyses. It reports no serious adverse events or deaths in the listed safety groups, and 1 participant with a non-serious adverse event in the PALs group. The reason for termination and additional analysis details are not reported in the registry record.