This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Comparison of Two New Silicone Hydrogel Multifocal Products (NCT00823615), a randomized na study. The primary outcome is Corrected Distance Binocular Visual Measurement in Normal Illumination Reported as Binocular Distance Visual Acuity.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00823615 |
| Phase | NA |
| Condition | Presbyopia |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Single |
| Enrollment | 40 |
| Arms in the primary outcome | 2 |
| Lead sponsor | CIBA VISION |
| Results posted | Yes |
2. Clinical Question
Population
Participants with presbyopia were enrolled. The primary outcome analysis was per protocol and excluded major protocol deviations identified by masked review. The registry record reports 40 enrolled participants; the outcome summaries include 33 participants for each lens.
Intervention
One study lens was the Lotrafilcon B multifocal contact lens. In one sequence, participants wore Lotrafilcon B followed by Senofilcon A.
Comparator
The other lens was the Senofilcon A multifocal contact lens. The alternate sequence was Senofilcon A followed by Lotrafilcon B. The registry describes the design as a crossover, so each sequence involved wearing both lenses in a different order.
Primary question
The primary comparison concerned corrected binocular distance visual acuity in normal illumination after 1 week of wear. The outcome was measured in logMAR units. The posted means were -0.08 for Lotrafilcon B and -0.04 for Senofilcon A, with a reported mean difference of 0.04 for Senofilcon A relative to Lotrafilcon B. Because positive logMAR values indicate poorer acuity, the difference points toward poorer measured acuity for Senofilcon A on this outcome. The registry also reports a confidence interval and p-value; interpretation should take account of the per-protocol population and the crossover design.
3. Trial Design
The registry record describes a randomized, single-masked, crossover trial comparing Lotrafilcon B and Senofilcon A multifocal contact lenses. The study concerned presbyopia and listed the two lenses as device interventions. One sequence wore Lotrafilcon B followed by Senofilcon A; the other wore Senofilcon A followed by Lotrafilcon B. In a crossover design, participants receive multiple interventions in sequence, allowing outcomes under different interventions to be compared within the same participant when the analysis uses the paired structure. The registry record does not report whether the posted comparison used paired observations or how treatment sequence was handled in the statistical analysis.
The registry lists 40 enrolled participants and records the trial as completed. The start is listed as 2008-12 and primary completion as 2009-02. The reported primary outcome summaries include 33 participants for each lens, while the per-protocol population is described as excluding major protocol deviations following masked review. The record does not explain the difference between enrollment and the outcome analysis counts, nor does it report participant flow or reasons for exclusion.
The listed masking is single, but the registry record does not identify which people were masked or describe how masking was maintained. It does not report period lengths beyond the primary endpoint timeframe of after 1 week of wear, any washout between lenses, or details of sequence allocation. The phase is listed as NA. The record identifies CIBA VISION as sponsor. Further protocol details, including the trial's original sample-size justification and planned statistical analysis, 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: Two participants were enrolled but not dispensed due to failing inclusion criteria. These participants were included in the Actual Enrollment calculation, but not Participant Flow or Baseline Characteristics calculations.
Period 1
| Stage | Lotrafilcon B / Senofilcon A | Senofilcon A / Lotrafilcon B |
|---|---|---|
| STARTED | 19 | 19 |
| COMPLETED | 19 | 19 |
| NOT COMPLETED | 0 | 0 |
Period 2
| Stage | Lotrafilcon B / Senofilcon A | Senofilcon A / Lotrafilcon B |
|---|---|---|
| STARTED | 19 | 19 |
| COMPLETED | 16 | 17 |
| NOT COMPLETED | 3 | 2 |
Reasons for not completing this period:
| Reason | Lotrafilcon B / Senofilcon A | Senofilcon A / Lotrafilcon B |
|---|---|---|
| Lost to Follow-up | 2 | 0 |
| Time/Job Conflict | 1 | 2 |
Analysis population for the primary outcome, as defined in the registry: Per protocol. Analysis excluded major protocol deviations as determined by masked review.
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.
| Characteristic | Unit | Overall |
|---|---|---|
| Participants analysed | 38 | |
| Age Continuous | years | 47.6 (SD 4.7) |
| Sex: Female, Male: Female | Participants | 30 |
| Sex: Female, Male: Male | Participants | 8 |
6. Primary Endpoint
The registry lists the primary outcome as Corrected Distance Binocular Visual Measurement in Normal Illumination Reported as Binocular Distance Visual Acuity, measured over After 1 week of wear.
| Element | Registry entry |
|---|---|
| Result type | Mean |
| Measure of spread | Standard Deviation |
| Unit | LogMAR |
| Endpoint classification | Continuous Endpoint |
The primary endpoint was corrected distance binocular visual measurement in normal illumination, reported as binocular distance visual acuity in logMAR units. Testing used distant reading charts and both eyes together under normal lighting. The stated timeframe was after 1 week of wear. This outcome captures distance acuity under a defined viewing condition, rather than near vision or performance under different illumination.
LogMAR expresses visual acuity on a scale tied to the logarithm of the minimum angle of resolution. The registry description states that 0.0 corresponds to 20/20 Snellen acuity and is considered normal. Positive values indicate poorer visual acuity, while negative values indicate better acuity. Consequently, the direction of a difference matters: a more positive result represents poorer measured acuity on this scale.
Visual acuity is used as a continuous outcome because it can be summarized by a mean and standard deviation, retaining gradations in measured performance rather than reducing results to a binary category. The posted results report a mean and standard deviation for each lens. The population for this primary outcome was per protocol, with major protocol deviations excluded after masked review. The registry record does not describe the exact testing instrument, measurement repeatability, or other endpoint procedures beyond the chart-based binocular assessment.
7. Results Posted in the Registry
- Senofilcon A Multifocal Contact Lens: mean -0.04 versus -0.08 on control; difference 0.04 (95% CI 0.02 to 0.06), standardized effect d = 0.78; z-test p = 0.001.
Mean difference: Senofilcon A Multifocal Contact Lens
95% CI: 0.02 to 0.06
Recalculated from the posted summary statistics
8. Statistical Interpretation
For the per-protocol outcome population, the reported mean logMAR acuity was -0.08 with Lotrafilcon B and -0.04 with Senofilcon A. The registry reports a mean difference of 0.04 for Senofilcon A relative to Lotrafilcon B, with a confidence interval from 0.015 to 0.065 and p = 0.001. Since higher, more positive logMAR values indicate poorer visual acuity, the direction of the reported difference is toward poorer measured acuity with Senofilcon A on this endpoint. This is a description of the posted measurements, not advice about lens choice or a conclusion about broader clinical performance.
The interval is entirely above zero, and the reported p-value is small under a conventional null comparison of no mean difference. Those statistics indicate that the posted group summaries are inconsistent with a zero difference under the assumptions behind that comparison. They do not establish how important the measured difference is to participants: the registry record does not provide a threshold for a clinically meaningful difference. Nor does a p-value quantify the probability that either lens is better or that the observed difference will recur in another study.
The mean values are close on the logMAR scale, but the scale's interpretation should not be replaced by an unsupported conversion. The registry description gives the meaning of 0.0 and the direction of positive and negative values; it does not provide a separate clinical interpretation threshold for this comparison. The reported standard deviations were 0.04 for Lotrafilcon B and 0.06 for Senofilcon A. These describe participant-level spread in the summaries, not the uncertainty of the mean difference by themselves.
The trial is described as crossover, but the registry's posted comparison does not report whether within-participant pairing was incorporated, how sequence or period effects were handled, or whether carryover was assessed. This is important because a crossover study's statistical analysis can use the fact that participants experienced both lenses; analyses that disregard within-participant dependence can characterize uncertainty differently. The record does not provide an analysis method that resolves this question. The posted means and comparison should therefore be read with the reported design and this missing analysis detail in mind.
The endpoint analysis was per protocol rather than an explicitly described analysis of all randomized participants. The record says major deviations were excluded after masked review, but it does not list exclusions, explain how missing measurements were handled, or report a participant flow. The outcome counts are 33 for each lens, against 40 enrolled overall. Thus, the posted comparison pertains to the analyzed per-protocol observations, and the record does not establish how those observations represent all enrolled participants.
There are no posted secondary outcome results and no posted analyses listed in the record. The findings therefore address the specific visual acuity endpoint and timeframe, not other aspects of lens performance. Safety reporting is also limited to the adverse-event figures recorded. The outcome and safety data do not provide a complete assessment of all possible effects, all follow-up periods, or outcomes not reported in the registry.
9. Statistical Methods Explained
The primary endpoint is continuous: each participant's binocular distance visual acuity was recorded on a logMAR scale, and the registry reports means and standard deviations. A mean gives the arithmetic center of the recorded values. A standard deviation describes how dispersed individual observations are around that mean. It is not a confidence interval, and it does not by itself show how precisely the group mean or between-lens difference has been estimated.
What does a mean difference represent?
The posted comparison reports a mean difference of 0.04 for Senofilcon A relative to Lotrafilcon B. In general, a difference in means is the mean for one group minus the mean for the reference group. Here, the comparator means are -0.04 for Senofilcon A and -0.08 for Lotrafilcon B, and the reported difference is positive. The endpoint description establishes that more positive logMAR values indicate poorer acuity. The direction of the estimate therefore corresponds to poorer measured acuity for Senofilcon A in this comparison. The estimate describes the observed endpoint on its stated scale; it should not be translated into another scale or a clinical threshold absent such information in the registry record.
How should the p-value be read?
The registry reports p = 0.001 for the comparison. In general, a p-value assesses how compatible the observed data are with a specified null hypothesis, under the statistical model used. It is not the probability that the null hypothesis is true, and it is not a measure of clinical importance. The record does not state the full statistical model, whether the test was paired, or whether the reported p-value was adjusted for multiple testing. It should therefore be read as the p-value attached to the posted comparison, not as a complete account of all analytic choices.
Why does crossover structure matter?
In general, crossover trials expose participants to more than one intervention in a planned sequence. When measurements from the same participant are compared across interventions, they are correlated rather than independent. A paired analysis accounts for that relationship and can remove some between-person variability from the treatment comparison. A suitable analysis may also need to consider sequence and period. These are general principles; the registry record does not report the model used for the posted result, whether pairing was used, or how period, sequence, or carryover were handled. The two reported outcome counts do not identify whether the observations are paired participant by participant.
The order of lens use can matter in a crossover study if outcomes change with time or if the first intervention influences the later period. General crossover methods often consider such possibilities in design and analysis. The registry record gives the two sequences but does not report a washout period, period-specific results, or a carryover assessment. These omissions do not show that such effects occurred; they mean the record does not make their handling clear.
What does the per-protocol label imply?
The primary outcome population is described as per protocol. The registry says major protocol deviations were excluded after masked review. In general, a per-protocol analysis focuses on participants who meet specified adherence or eligibility criteria, while an intention-to-treat analysis aims to retain participants according to randomized assignment. These approaches answer related but not identical questions. The record does not report an intention-to-treat analysis, the criteria used to define major deviations, or the number and characteristics of exclusions. The per-protocol results should thus be understood as applying to the analyzed population as defined in the record, not automatically to every enrolled participant.
How do confidence intervals complement the estimate?
A confidence interval describes a range of values compatible with the data and the method used to calculate it. In repeated use of the same procedure under its assumptions, intervals at a stated confidence level would capture the underlying parameter at the corresponding rate. The registry lists a confidence interval for the mean difference, and both reported endpoints are positive. This indicates that zero is not inside the posted interval. The confidence level and the exact calculation method are not reported in the registry record, so those details should not be assumed. General interval interpretation also depends on the validity of the model and the analysis population.
The posted standard deviations, 0.04 and 0.06, describe dispersion in each lens summary. The comparison also reports a pooled standard deviation of 0.051 and a standardized difference of 0.784. These standardized statistics put the observed mean contrast in relation to variability, but their relevance depends on the chosen analysis and assumptions. The registry record does not report a prespecified threshold for interpreting the standardized effect, nor does it explain whether this statistic was part of the sponsor's planned analysis. It should not replace interpretation on the endpoint's original logMAR scale.
What is and is not known about the analysis plan?
The registry lists two outcome measures and no posted analyses. It does not report a protocol-level analysis plan, a sample-size justification, interim analyses, missing-data methods, or multiplicity procedures. These are not details that can be inferred from the p-value or the outcome summaries. General statistical practice distinguishes analyses planned before results are known from analyses selected after data review, but the registry record does not establish which applies to the posted comparison. The comparison should be described as posted, with no unsupported claim about prespecification.
In general, multiplicity arises when several outcomes, timepoints, or comparisons are tested: the chance of at least one false-positive result can increase if each test is interpreted separately without an adjustment strategy. This record reports no secondary posted results and no analyses listed, but it does not say whether other analyses were planned or performed. It is therefore not possible to establish from the record whether multiplicity was relevant to the sponsor's analysis or how it was managed.
10. Confidence Intervals and Precision
The registry reports a mean difference of 0.04 for Senofilcon A relative to Lotrafilcon B, with a confidence interval from 0.015 to 0.065. The interval lies above zero, so the range of values compatible with the posted calculation does not include no difference. The reported p-value is 0.001. Together, these indicate a comparatively precise estimate in the context of the stated calculation, while still leaving uncertainty about the magnitude of the underlying difference.
A confidence interval is more informative than a point estimate alone because it communicates uncertainty around the estimated contrast. It does not mean that every value inside the interval is equally likely, and it is not a guarantee that the true difference lies within these particular endpoints. Its interpretation depends on the method and assumptions used. The confidence level and calculation method are not reported in the registry record. Also, because the design is crossover and the record does not state whether pairing or period effects were handled, the interval cannot be fully evaluated from the posted information alone.
The observed outcome summaries are based on 33 participants for each lens in the per-protocol population. The group standard deviations were 0.04 for Lotrafilcon B and 0.06 for Senofilcon A. These values convey variation in individual acuity results; they are not uncertainty bounds for the mean difference. The available counts and summaries do not describe missing measurements, excluded participants, or how participant-level correlation was addressed. Precision should therefore be understood as the precision reported for the comparison, rather than as a complete account of uncertainty from every design and analysis issue.
The interval's direction supports the same interpretation as the estimate: the difference is positive when expressed as Senofilcon A relative to Lotrafilcon B, and more positive logMAR indicates poorer acuity. The record does not state what interval width or difference would be clinically important. Statistical precision and clinical importance are separate considerations.
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.
| Effect to detect | Participants per arm, 80% power | Participants per arm, 90% power |
|---|---|---|
| 100% of the observed effect | 26 | 35 |
| 75% of the observed effect | 46 | 61 |
| 50% of the observed effect | 103 | 137 |
The sample-size figures are planning illustrations based on the observed effect, not the original trial's sample-size design. The assumptions are a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Each planning row considers detecting a stated fraction of the observed effect. These figures are participants per arm, not total participants or total events, because this is not a time-to-event outcome.
The 80% power column gives the number of participants per arm that the planning calculation estimates would be needed to have an 80% chance of detecting the specified effect under the stated assumptions, if that effect and model were applicable. The 90% power column uses a higher target chance of detecting that effect, and therefore requires more participants per arm in each listed scenario. These are planning quantities, not a description of what the completed trial achieved.
The rows consider 100% of the observed effect, 75% of the observed effect, and 50% of the observed effect. The corresponding figures are 26 and 35 participants per arm for 80% and 90% power when planning for 100% of the observed effect; 46 and 61 when planning for 75%; and 103 and 137 when planning for 50%. The smaller the effect a study is intended to detect, the more participants are generally needed, all else equal. This pattern is visible across the planning scenarios.
This is not observed power. The original design assumptions and sample-size justification are not reported in the registry record. The planning figures use the observed estimate as their starting point, and they do not show that the trial was designed with any particular power or that its findings have a particular probability of replication.
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 z1−α/2 = 1.960) and the desired power (z1−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
- Observed difference Δ = 0.040; pooled standard deviation σ = 0.051.
- n = 2 × (1.96 + 0.842)2 × 0.0512 / 0.0402 = 25.5, rounded up to 26 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 <- 0.04 # observed difference in means
sigma <- 0.0509901951359278 # 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(823615)
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 = 26 (80% power), 35 (90% power)
75% of observed effect: n per arm = 46 (80% power), 61 (90% power)
50% of observed effect: n per arm = 103 (80% power), 137 (90% power)
power.t.test: 26.5
Simulated power at n = 26 per arm: 0.792 (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 record lists two outcome measures but reports no posted secondary outcome results and no analyses listed. The available result is the primary binocular distance visual acuity endpoint after 1 week of wear. The record does not report whether additional endpoints, comparisons, timepoints, or subgroup analyses were planned or performed outside the posted results.
Multiplicity is a general statistical concern when several hypotheses are tested. If many tests are interpreted without an adjustment, the chance of at least one apparently notable result can rise. The registry record does not report a multiplicity adjustment or a strategy for controlling that risk. It would not be justified to conclude that no multiplicity issue existed merely because no secondary analyses are posted; nor is there enough information to determine whether any correction was appropriate or used.
Missing-data handling is also not reported. The outcome summaries include 33 participants for each lens, while overall enrollment is 40. The record does not explain whether the difference reflects missing outcomes, protocol exclusions, or other reasons. It says the primary population was per protocol and that major protocol deviations were excluded after masked review, but gives no participant flow, counts by exclusion reason, imputation method, or sensitivity analysis. Consequently, the extent and possible influence of missing data cannot be evaluated from the registry record.
The stated primary analysis population is per protocol. The record does not report an intention-to-treat analysis or clarify whether all randomized participants were analyzed according to assigned sequence. It also does not identify the criteria for defining major protocol deviations. Per-protocol results can differ from results using all randomized participants if exclusions relate to outcomes or treatment experience; this is a general possibility, not a finding about this trial.
The crossover design creates further analysis questions. The registry describes sequences but does not report whether the analysis accounted for within-participant pairing, period, sequence, or potential carryover. These are not evidence of a flaw; they are details needed to assess the statistical analysis and are not reported in the registry record.
14. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Lotrafilcon B Multifocal Contact Lens | 0 | 39 | 0.0% |
| Senofilcon A Multifocal Contact Lens | 0 | 38 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Lotrafilcon B Multifocal Contact Lens | 0 of 39 |
| Senofilcon A Multifocal Contact Lens | 0 of 38 |
The registry reports serious adverse events for 0 of 39 participants at risk in the Lotrafilcon B group and 0 of 38 participants at risk in the Senofilcon A group. It also reports other adverse events for 0 of 39 and 0 of 38, respectively. These are the recorded figures for the listed at-risk groups. They should not be read as proof that no adverse experiences occurred outside the categories or reporting captured in the registry.
The record does not list serious adverse-event terms. Death counts are not reported in the registry record. The safety group counts are not the same as the primary outcome counts, which were 33 for each lens in the per-protocol analysis. The record does not explain the difference in denominators, provide event narratives, or describe the safety observation period in detail. It also does not provide information that would establish whether adverse events were collected in the same way across periods of this crossover study.
Zero recorded events in these groups is a limited descriptive result. It does not establish the absence of risk, particularly when the number observed and the reporting details are limited. No treatment recommendation follows from these figures.
15. What the Result Does, and Does Not, Mean
The posted result describes binocular distance visual acuity in normal illumination after 1 week of wear among the per-protocol participants. Mean logMAR was -0.08 with Lotrafilcon B and -0.04 with Senofilcon A. The reported mean difference was 0.04 for Senofilcon A relative to Lotrafilcon B. Since more positive logMAR values indicate poorer acuity, the measured difference favors Lotrafilcon B in direction on this specific endpoint. The reported confidence interval is entirely positive, and the comparison has p = 0.001.
This finding does not by itself establish how noticeable or important the difference is to participants. The registry record does not give a clinically meaningful threshold for logMAR differences, and statistical evidence against a zero difference is not the same as evidence of a meaningful benefit. The result is limited to the specified distance acuity measurement, lighting, and timeframe. It does not establish comparative performance for near vision, comfort, sustained use, other visual tasks, or longer follow-up because those results are not posted.
The trial is described as randomized, single-masked, and crossover. However, the record does not explain which parties were masked or how the analysis incorporated paired observations and treatment order. It also does not report a washout, missing-data procedures, or a complete participant flow. The primary analysis was per protocol, with major deviations excluded after masked review; how that population differs from all enrolled participants is not specified.
The adverse-event figures record zero serious and zero other events in the listed at-risk groups, but death counts are not reported in the registry record. These limited registry figures should not be interpreted as proving there were no safety concerns. Overall, the result is a focused statistical comparison of one reported visual acuity endpoint, with uncertainties about analysis details and applicability beyond the recorded population and conditions.
16. Why This Trial Matters Statistically
This trial is statistically instructive because it combines a continuous visual acuity endpoint with a randomized crossover design. The means and standard deviations summarize acuity on a scale whose direction is important: more positive logMAR values indicate poorer visual acuity. The mean difference is positive for Senofilcon A relative to Lotrafilcon B, so interpreting the sign correctly is essential before discussing the comparison.
Crossover trials can make efficient use of participant-level comparisons because each participant may receive both interventions. That advantage depends on analyzing the resulting within-person correlation appropriately and considering sequence and period. The registry record describes the two treatment orders but does not report whether the analysis used paired data or addressed these design features. This makes the example a reminder that a posted estimate and p-value are not enough to reconstruct the analysis.
The reported confidence interval and p-value communicate statistical uncertainty and evidence against a zero difference under the applied calculation. They do not answer whether the difference is clinically important. The registry provides no clinical importance threshold, and its primary analysis is per protocol. Without the exclusion details and full participant flow, the link between the analyzed group and the full enrolled population also remains uncertain.
Finally, planning calculations based on the observed effect can illustrate how sample-size requirements change when a study targets smaller effects, but they are not evidence about the design choices of the completed trial. The original sample-size justification is not reported in the registry record. Separating observed findings, uncertainty, design assumptions, and missing analysis details is central to responsible interpretation of this trial.
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.
Several trial-specific details needed for a fuller assessment are not reported in the registry record. Although the design is listed as crossover and both treatment sequences are described, the record does not give the period duration, any washout interval, or the statistical handling of sequence, period, or carryover. It does not specify whether the comparison used paired participant-level data. These details matter to evaluating uncertainty in a crossover comparison.
The primary outcome population was per protocol, excluding major protocol deviations after masked review. The record does not report how many participants were excluded, the reasons for exclusion, the criteria used to identify major deviations, or participant flow by sequence. Enrollment was 40, while each primary outcome summary contains 33 participants; the record does not explain this difference. Missing-data methods and sensitivity analyses are not reported.
The masking designation is single, but who was masked and how are not specified. The record does not report the original sample-size justification, analysis plan, interim analyses, multiplicity procedures, or confidence-interval calculation method and confidence level. It also does not provide a threshold for clinical importance on the logMAR scale.
The primary result concerns only binocular distance acuity under normal illumination after 1 week of wear. No secondary outcome results are posted, and no analyses are listed. Safety information is limited to the recorded event counts; death counts are not reported in the registry record, and additional detail about event collection and observation time is absent. These limitations restrict interpretation to the posted results and make it difficult to assess broader performance or longer-term outcomes.
18. Related Tutorials
19. Related Statistical Calculators
20. Sources
- ClinicalTrials.gov: Comparison of Two New Silicone Hydrogel Multifocal Products — NCT00823615.
- Registry record last updated 2012-06-29; status last verified 2012-01.
- Results first posted 2010-10-29.
- 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.
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21. Record Summary
The registry record describes a completed, randomized, single-masked crossover trial of Lotrafilcon B and Senofilcon A multifocal contact lenses in participants with presbyopia. Enrollment was 40. The primary endpoint was corrected binocular distance visual acuity in normal illumination after 1 week of wear, measured in logMAR units. The per-protocol summaries included 33 participants per lens.
Mean acuity was -0.08 for Lotrafilcon B and -0.04 for Senofilcon A. The reported mean difference for Senofilcon A relative to Lotrafilcon B was 0.04, with a confidence interval from 0.015 to 0.065 and p = 0.001. Higher logMAR values indicate poorer acuity. The record lists zero serious and zero other adverse events in the respective at-risk groups; death counts are not reported in the registry record.
The record does not report the original sample-size justification, detailed crossover analysis, missing-data methods, or multiplicity procedures. No secondary outcome results or analyses are posted.