Randomized Contralateral Clinical Trial With Single-piece (SN60WF) vs. Three Piece (MA60AC) AcrySof Intraocular Lenses (IOLs) on Development of Posterior Chamber Opacification (PCO).: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Randomized Contralateral Clinical Trial With Single-piece (SN60WF) vs. Three Piece (MA60AC) AcrySof Intraocular Lenses (IOLs) on Development of Posterior Chamber Opacification (PCO). (NCT00758745), a non-randomized na study. The primary outcome is Posterior Capsule Opacification (PCO).

2. Clinical Question

The trial title and brief summary describe a randomized contralateral clinical trial. However, the registry record labels allocation as non-randomized and notes that the arms are not a like-for-like control comparison. That distinction matters when interpreting any apparent difference: without a reported allocation method and analysis, the record cannot establish how well the groups or eyes can be compared. The record also labels the model as parallel, which does not resolve the contrast between the contralateral description and the non-randomized allocation label.

The clinical question is therefore identifiable, but the answer is not available from the posted outcome information. The record identifies the lens models, the condition, and the primary endpoint, yet does not report the observed EPCO scores, their variability, or a treatment comparison. It is not possible to tell from these entries whether either lens had a higher or lower mean PCO score, or how precise any difference would be.

3. Trial Design

The registry record describes a completed clinical trial sponsored by Alcon Research. It lists a start in 2006-01, primary completion in 2009-12, and enrollment of 81. The phase is listed as NA. Cataract is the listed condition. These entries describe the record’s basic context; they do not provide participant-level information or a detailed account of conduct.

The two device interventions are Model SN60WF and Model MA60AC. Their descriptions identify implantation with the corresponding AcrySof intraocular lens. The title and brief summary characterize the study as randomized and contralateral, while the allocation field says non-randomized. The model field says parallel, and masking is listed as none. The record therefore contains design labels that do not all point to the same interpretation. In particular, the non-randomized allocation label means the arms should not be treated as a like-for-like control comparison.

A contralateral design generally refers to comparing treatments assigned to opposite sides or eyes of the same participant. As a general statistical matter, paired observations from the same person are related, so an analysis often needs to account for that dependence. The record’s title and summary use contralateral wording, but the available design fields do not explain how eyes were assigned, whether each participant received both lens models, or how the outcome analysis handled any pairing. Those details are not reported in the registry record.

The record lists one primary outcome measure and zero analyses. It does not report the methods used to analyze the outcome, the number of participants contributing to the primary endpoint, or whether the analysis followed an intention-to-treat or another population definition. The recorded enrollment alone cannot answer those questions. It also does not show whether follow-up was complete through the stated endpoint timeframe of up to 3 years.

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

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 Posterior Capsule Opacification (PCO), measured over Up to 3 years.

The primary endpoint is Posterior Capsule Opacification (PCO), reported as a mean on a scale in units on a scale, with standard deviation as the dispersion measure. The timeframe is up to 3 years. PCO is assessed using the EPCO score, which combines a clinical grade of opacification density with the fraction of capsule area involved behind the intraocular lens optic.

The grading description runs from no detectable opacification to severe detectable opacification, with intermediate categories for minimal, mild, and moderate detectable opacification. An individual score is calculated by multiplying the opacification grade by the fraction of capsule area involved. The record notes that selection and grading of areas are subjective. Thus, EPCO is a structured measure, but its assessment includes clinical judgment rather than being wholly objective.

As a general measurement concept, using a defined scale allows investigators to describe and compare an outcome consistently, while a mean conveys the average score in a group. The standard deviation describes how spread out individual scores are around that mean; it is not the uncertainty of the mean itself. Interpretation depends on the scoring process, the amount of outcome data available, and how the comparison is analyzed.

The registry record does not report the mean PCO scores, standard deviations, or a between-model estimate. It therefore does not permit a conclusion about the observed endpoint or the precision of a comparison. Nor does the endpoint description establish that the score captures every aspect of capsule opacification; it defines the specific measure chosen for this trial.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The record specifies a continuous primary measure summarized by a mean and standard deviation, but it does not report a statistical analysis for that measure. The explanations below describe general statistical ideas relevant to such data; they are not claims about methods used in this trial.

What does a mean describe?

For a continuous outcome, the mean is the arithmetic average of observed scores in a defined group or analysis population. It provides a compact description of the group’s central level, but it does not show the full distribution. Different distributions can have the same mean, and unusual values can influence it. In this trial, the endpoint is an EPCO score, formed from a grade and the fraction of capsule area involved. The registry record identifies the planned summary as a mean but gives no observed mean.

What does the standard deviation describe?

The standard deviation describes the spread of individual values around their group mean. A larger standard deviation indicates more dispersion in the measured values; it does not directly describe how uncertain the estimated mean is. The precision of a mean estimate also depends on how many observations contribute and on the analysis design. The record lists standard deviation as the outcome’s dispersion measure but does not give any values or the number of participants contributing outcome data.

Why can a contralateral design affect analysis?

In general, observations from two eyes in the same person are not necessarily independent. Shared characteristics can make paired outcomes more alike than outcomes from different people. A paired comparison uses the relationship between the two measurements; an analysis that ignores that relationship can produce an inappropriate estimate of uncertainty. The trial title and summary describe a contralateral design, but the registry record does not report the allocation procedure or the statistical handling of paired outcomes. It is therefore not possible to determine whether a paired method was used or whether the posted outcome data follow that structure.

The non-randomized allocation label is also important. General statistical reasoning distinguishes randomized assignment, which can support comparability by balancing measured and unmeasured factors on average, from non-randomized assignment, where systematic differences may remain. Adjustment methods can sometimes account for measured differences, but they cannot guarantee removal of unmeasured confounding. The record does not report an adjustment strategy, baseline comparisons, or enough detail to assess confounding. No claim about the success of any such method is warranted.

What do confidence intervals and p-values contribute?

In general, a confidence interval expresses uncertainty around an estimated quantity under a statistical model and its assumptions. For a comparison, an interval around the estimated difference can indicate which values are reasonably compatible with the observed data and method. Its width helps communicate precision. A p-value evaluates how unusual data at least as incompatible with a null hypothesis would be if that null model and its assumptions held. It is not the probability that the null hypothesis is true, nor does it measure the size or importance of an effect.

Neither a confidence interval nor a p-value for the primary outcome is reported in the registry record. Without an estimate and its uncertainty, no inferential conclusion can be reconstructed. It would be inappropriate to infer a null result from the absence of a reported test.

Why might over-dispersion matter?

In general, over-dispersion means that observed variability is greater than a statistical model expects. If a model understates variability, its standard errors may be too small and its confidence intervals too narrow. For a continuous score, analysts may examine the distribution and residual behavior to decide whether a simple model is adequate. The registry record does not report a model, diagnostic checks, or any over-dispersion assessment. The point is a general consideration, not a finding about these data.

The EPCO description also notes subjective selection and grading of areas. In general, subjective measurement can introduce variation between assessors or occasions. Training, masking, and reproducibility procedures can be relevant, but the registry record lists masking as none and does not describe assessor procedures or reliability checks. No further detail about measurement quality is reported.

What do the planning illustrations mean?

The stated planning approach uses a two-sided significance level of 0.05, equal allocation, and a normal approximation, with the effect to detect defined as a stated fraction of the observed effect. These are assumptions for planning illustrations based on the observed effect, not the trial’s own design justification. A planning calculation asks how many participants per arm might be needed under chosen assumptions. Its answer changes with the target effect, variability, significance level, power target, and analysis model. The record does not report the trial’s sample-size justification, and the illustrations are not observed power.

In general, observed power calculated after a study from its estimated effect does not replace an estimate and confidence interval. When a result is imprecise, the confidence interval communicates the range of effects compatible with the data more directly. In this record, there are no primary outcome estimates to interpret, and no result-specific uncertainty measure is reported. The planning assumptions cannot fill that gap.

Finally, the listed enrollment is not necessarily the number included in an endpoint analysis. Missing measurements, exclusions, or loss to follow-up can change the analyzed population and precision. The registry record does not report the number with outcome data, a missing-data method, or analysis-population definitions. Those omissions prevent assessment of how the analysis, if any, addressed incomplete follow-up.

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("Model SN60WF", "Model MA60AC")
n   <- c(60, 60)
m   <- c(0.18, 0.15)
sp  <- c(0.41, 0.44)
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  Model SN60WF  60  0.180  0.410  0.074  0.286
CARM  Model MA60AC  60  0.150  0.440  0.036  0.264

11. Multiplicity, Missing Data and Analysis Populations

The record lists one primary outcome measure, PCO, and zero analyses. It does not report whether there were secondary outcomes, multiple time points, subgroup comparisons, or multiple statistical tests beyond the one listed measure. No multiplicity strategy, such as a procedure to control the chance of false-positive findings across multiple tests, is reported in the registry record. Because no primary analysis result is reported, there is no basis to assess whether multiplicity affected an inference.

Missing-data information is also not reported in the registry record. The outcome timeframe is up to 3 years, but there is no account of how many participants had an EPCO assessment, whether measurements were missed, or why data might be unavailable. The record does not describe imputation, a complete-case analysis, sensitivity analyses, or another missing-data approach. These details matter because the amount and pattern of missingness can affect both the estimated outcome and its uncertainty.

The analysis population is not defined in the record. It does not say whether all enrolled participants, all treated participants, or only those with evaluable endpoint measurements were included in any primary analysis. Enrollment of 81 cannot identify the analysis denominator. The registry record also does not report how the study handled participants with data from only one eye or any dependence between paired eye measurements.

Without these details, it is not possible to evaluate the robustness of an outcome estimate to missingness, population selection, or multiple testing. No particular missing-data or multiplicity problem can be asserted; rather, the relevant methods and counts are not reported in the registry record.

12. Safety Results

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

Other (non-serious) adverse events

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

For Model SN60WF, the record lists 81 at risk for serious adverse events and 0 affected; it also lists 81 at risk for other adverse events and 0 affected. For Model MA60AC, the corresponding entries are 81 at risk and 0 affected for serious adverse events, and 81 at risk and 0 affected for other adverse events. Deaths are not reported in the registry record.

These entries mean that the registry lists no affected participants in the displayed adverse-event categories for either group. They do not establish that no adverse events occurred outside the recorded categories, or that all participants were observed for the same duration. The record does not provide event definitions, follow-up completeness, event-level descriptions, or a comparative safety analysis. It also does not explain the relationship between the adverse-event group denominators and the enrollment entry.

Zero recorded events should not be read as proof that the underlying risk is zero. As a general statistical point, the absence of observed events can still be compatible with some nonzero event risk, particularly when the amount of observation and follow-up are not fully described. These counts are descriptive registry entries and do not establish a safety difference between the lens models.

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

The record establishes that a clinical trial was registered to assess posterior capsule opacification associated with two AcrySof intraocular lens models. It specifies an EPCO score as the primary outcome, summarized as a mean with standard deviation, and gives a timeframe of up to 3 years. It also records an enrollment of 81 and labels the trial completed.

The record does not establish what the trial found about PCO. No mean scores, standard deviations, contrast between models, confidence interval, or p-value are reported. Accordingly, the posted results do not show whether the observed scores differed, how large any difference was, or how precisely it was estimated. The absence of an outcome result cannot be interpreted as evidence of equivalence, and it cannot support a conclusion that one model had higher or lower PCO.

The design description also requires caution. The title and brief summary describe randomization and a contralateral comparison, but the allocation field says non-randomized. The record warns that the arms are not a like-for-like control comparison. Without clarification of assignment and analysis, a causal interpretation would be unsupported. If measurements were paired within participants, that relationship would also need to be handled appropriately, but the method is not reported.

As a general distinction, statistical significance and clinical importance are not interchangeable. A small estimated difference could be precise, or a larger difference could be uncertain; interpretation requires the estimate, its uncertainty, and context for the scale. None of those result-level details is available for PCO in this registry record. The EPCO scoring description provides a measurement framework, but it does not supply a threshold for a meaningful difference.

The adverse-event entries list zero affected participants for the serious and other adverse-event categories in both groups, with 81 at risk in each listed entry. They are not a complete account of event types, duration of observation, or comparative risk. The record therefore supports only a limited descriptive reading of those counts, not a broad safety conclusion.

In short, the study question and measurement are documented, but the clinical outcome comparison is not. The registry record does not provide the results needed to judge the direction, magnitude, precision, or clinical meaning of an effect.

14. Why This Trial Matters Statistically

This trial is statistically notable because its descriptions raise a design-interpretation issue. The title and brief summary call it randomized and contralateral, while the allocation field labels it non-randomized and a registry note cautions that the arms are not a like-for-like control comparison. Those distinctions are central to understanding what a comparison could establish. Randomization, pairing, and the analysis unit each affect how data should be interpreted, but the record does not clarify how these features were implemented.

The outcome also illustrates the difference between a defined measurement and an available result. The EPCO score has a described grading scheme and combines opacification density with the fraction of capsule area involved. The record notes that selection and grading are subjective. Defining a scale can make an outcome interpretable, but the absence of observed scores and analysis means the reader cannot evaluate the actual comparison or its precision.

From a statistical perspective, a contralateral setup can create paired data, while the registry model is labeled parallel. Those terms can carry different implications for design and analysis. The record does not give enough detail to reconcile them. Recognizing that ambiguity is important: an analysis suited to independent groups may not be appropriate for paired observations, and an analysis must match the way observations were collected.

The record is also a useful reminder that enrollment and a planning illustration do not show the strength of an outcome result. The planning assumptions are not the trial’s own sample-size justification, and sample-size illustrations are not observed power. Without endpoint estimates and uncertainty, enrollment alone cannot establish whether the comparison was informative.

These features matter because statistical interpretation depends on more than the name of a study design or the presence of a listed endpoint. Clear allocation, analysis, outcome reporting, and missing-data information are needed to evaluate a comparison. In this case, those result and methods details are not reported in the registry record.

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 most direct limitation is the absence of primary PCO outcome results. The record specifies the EPCO score, its mean and standard deviation summaries, and a timeframe of up to 3 years, but does not provide the observed values or a comparison. Consequently, neither the direction nor precision of the endpoint result can be assessed.

There is a material ambiguity in the design information. The title and summary use randomized contralateral wording, while allocation is labeled non-randomized and the model is labeled parallel. The registry record explicitly cautions that the arms are not a like-for-like control comparison. It does not explain the allocation process, whether each participant received both lens models, or whether an analysis accounted for paired observations. This limits interpretation of any potential between-model contrast.

Outcome completeness and analysis populations are not described. Although the endpoint timeframe is up to 3 years, the record does not report how many participants contributed an outcome measurement, the extent or reasons for missing data, or the population included in analysis. No statistical analysis method, adjustment strategy, confidence interval, p-value, or sample-size justification is reported. Zero analyses are listed.

The endpoint’s description notes that area selection and grading are subjective, while masking is listed as none. The record does not describe assessor training, reliability, or procedures intended to reduce measurement variation. It is not possible to determine whether these considerations affected the data.

Safety reporting is limited to affected and at-risk counts for serious and other adverse events; deaths are not reported in the registry record. Event definitions, descriptions, observation duration, and follow-up completeness are not given. These limitations constrain what can be inferred from the recorded zero counts.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Randomized Contralateral Clinical Trial With Single-piece (SN60WF) vs. Three Piece (MA60AC) AcrySof Intraocular Lenses (IOLs) on Development of Posterior Chamber Opacification (PCO). — NCT00758745.
• Registry record last updated 2014-08-19; status last verified 2011-08.
• Results first posted 2011-07-28.
• 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

The registry record describes a completed study sponsored by Alcon Research, with enrollment of 81 and a start in 2006-01 and primary completion in 2009-12. Cataract is the listed condition, and phase is recorded as NA. The interventions are AcrySof Model SN60WF and Model MA60AC intraocular lenses.

PCO measured using the EPCO score is the primary outcome, with a mean and standard deviation specified for a timeframe of up to 3 years. The record lists one outcome measure and zero analyses. It reports no primary outcome values or comparative statistical results.

The title and summary describe a randomized contralateral clinical trial, but allocation is labeled non-randomized, the model is labeled parallel, and the registry record cautions that the arms are not a like-for-like control comparison. Serious and other adverse-event counts list 0 affected among 81 at risk in each lens group; deaths are not reported in the registry record. These entries describe what is recorded, but do not provide a basis for a comparative outcome or broad safety conclusion.