Patient Perception of Visual Distortions: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Patient Perception of Visual Distortions (NCT02203747), a registered phase not stated study. The primary outcome is Visual Distortion Symptoms.

2. Clinical Question

The study purpose is to evaluate visual distortions reported by pseudophakic patients. That purpose is reflected in a patient self-assessment rather than a reported objective measurement of visual performance. The endpoint is recorded at baseline, so the registry description does not establish a change from an earlier assessment or a response to a study intervention.

The comparison should be read as a comparison between two registry-listed groups, not as evidence from a randomized, like-for-like control design. The record does not state how allocation occurred. It also does not report the primary outcome values needed to answer the descriptive question quantitatively. Thus, the registry record identifies what the study intended to measure, but the posted results do not establish the level of symptoms in either group or the contrast between them.

3. Trial Design

The record identifies a completed study with enrollment of 79. It lists cataract and astigmatism as conditions and names Abbott Medical Optics as the sponsor. The study started in 2014-08, and primary completion is recorded as 2014-10. The stated purpose is to evaluate visual distortions reported by pseudophakic patients.

The registry lists administration of patient self-assessment as the intervention. It describes a toric-IOL arm whose participants were bilaterally implanted with toric IOLs and a non-toric-IOL arm whose participants were bilaterally implanted with non-toric IOLs. The registry explicitly indicates that allocation was not stated and that the arms are not a like-for-like control comparison. No further account of recruitment, assignment, masking, or the process by which participants came to receive either type of lens is reported in the registry record.

The primary outcome is a continuous measure summarized as a mean with standard deviation. It is a baseline rating of visual-distortion symptoms under overall conditions. The scale uses categories from 0, “did not experience,” to 3, “severe,” with lower values representing the best outcome. The record lists 2 outcome measures but 0 analyses. It does not report group-level primary outcome values or a statistical comparison.

The primary endpoint description notes that one participant in the toric-IOL group was excluded because of a protocol deviation: an improper method was used to simulate visual distortion. This note does not provide a complete analysis population definition, nor does it state how missing or unusable assessments in either group were handled. Although the adverse-event record reports group counts at risk, those counts should not be assumed to be the denominators used for the primary endpoint. The primary endpoint denominators are not reported in the registry record.

Overall, the record supplies a study purpose, group descriptions, a baseline patient-reported endpoint, and limited safety counts. It does not supply enough design or outcome detail to reconstruct the study’s analysis or treat the group comparison as a controlled estimate of a lens-related effect.

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

Analysis population for the primary outcome, as defined in the registry: Of the 45 subjects in the "Pseudophakic implanted with toric IOL" group, one (#102) was excluded due to a protocol deviation (improper method used to simulate visual distortion).

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 Visual Distortion Symptoms, measured over Baseline.

The primary endpoint is titled “Visual Distortion Symptoms.” It measures a participant’s subjective rating of visual-distortion symptoms under overall conditions at baseline. The response categories are “did not experience” (rating = 0), “mild” (rating = 1), “moderate” (rating = 2), and “severe” (rating = 3). The stated minimum score is 0 and the maximum score is 3; lower values represent the best outcome. The registry specifies that the endpoint is summarized as a mean with a standard deviation.

A patient self-assessment is relevant to a question about symptoms as experienced and reported by participants. It captures their response to the described scale, rather than a clinician’s rating or a device-based measurement. The mean provides a summary of ratings across an analysis group, while the standard deviation describes how dispersed individual ratings are around that mean. Neither statistic is reported for this endpoint in the registry record.

The endpoint’s numerical coding deserves care in interpretation. The response options have an order from no experience through increasing severity, but they are categories rather than a continuous instrument with many possible values. Treating the codes as a continuous measure and reporting a mean summarizes them as numbers. As a general statistical consideration, that summary can obscure which response categories participants selected and can depend on how the numerical steps are interpreted. The registry record does not provide category counts, group means, or standard deviations to assess the actual response distributions.

The measurement is specified at baseline. The record does not describe a change score, a follow-up symptom rating, or a treatment-response endpoint. Therefore, this endpoint description alone concerns symptom ratings at the stated assessment time and cannot establish improvement over time.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is described as a continuous measure summarized by a mean and standard deviation. Those terms explain how an outcome can be condensed, but they do not provide the result. The registry record gives no group means or standard deviations for visual-distortion symptoms, and it lists 0 analyses. Any interpretation of the endpoint therefore has to stop short of a numerical comparison.

What does a mean summarize?

A mean is the arithmetic average of the observations included in an analysis. It can describe the central level of a set of ratings, but it does not show the full distribution. For a rating scale with ordered categories, the same mean can arise from different patterns of responses. For example, a distribution concentrated around an intermediate category can have the same average as a mixture of low and high ratings. This is a general property of means, not a reported pattern in this study.

The scale runs from 0 to 3, with the categories “did not experience,” “mild,” “moderate,” and “severe.” These are ordered responses. A mean treats their numerical codes as having meaningful distances, even though the scale description establishes order and codes but does not demonstrate that the perceived step from one category to the next is equal. The mean is the registry’s specified summary, but category-level results would help readers understand the response pattern. Such counts are not reported in the registry record.

What does the standard deviation describe?

The standard deviation summarizes dispersion around the mean. A smaller standard deviation generally indicates that observations cluster more closely around the average, while a larger one indicates more spread. It is not a measure of uncertainty in the mean itself; that is a different concept. The standard deviation for either group is not reported in the registry record, so the variability of the observed ratings cannot be assessed.

In general, the mean and standard deviation are most informative when the numerical summary is a reasonable representation of the distribution. For bounded, ordered ratings, investigators may also consider the distribution across response categories and whether there are floor or ceiling concentrations. A floor concentration would mean many responses at the lowest score; a ceiling concentration would mean many at the highest score. These are general interpretive considerations, not findings about this study. The record contains no category frequencies or individual-level data with which to evaluate them.

What would a confidence interval add?

A confidence interval is a statistical range that expresses uncertainty around an estimated quantity under a specified analysis. For a group contrast, it can show which values are reasonably compatible with the data and model. Its width depends on factors including the amount of information in the observations and their variability. A confidence interval does not establish that the estimate is free of bias, and it does not remedy a non-comparable group design. No confidence interval for the primary endpoint is reported in the registry record.

A p-value, if reported, would address the compatibility of the data with a particular null hypothesis under the chosen statistical model. It would not measure the probability that a hypothesis is true, the size of an effect, or its practical importance. The record reports no primary endpoint test or p-value. The statistical test, model, and any adjustment for covariates are not reported in the registry record.

Why does over-dispersion matter?

Over-dispersion is a general issue for models that assume a particular level of variability: the observed data vary more than the model expects. If a model underestimates variability, its uncertainty estimates can be too small and its inferential results can be misleading. The relevance of over-dispersion depends on the outcome and model. The registry record does not identify a model for the primary endpoint, so it is not possible to assess whether over-dispersion was considered or whether it would be a concern for the actual analysis.

For this endpoint, the fact that ratings are bounded and categorical makes it important to understand their distribution before relying on a model-based summary. General options for ordered outcomes can preserve category order without assuming equal spacing, while a mean-based approach summarizes the numerical codes. Which approach was used beyond the registry’s stated mean and standard deviation is not reported. No model choice should be inferred from the endpoint description alone.

What do the planning assumptions mean?

The record describes a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between the arms, and a normal approximation. It states that the effect to detect is a stated fraction of the observed effect. For time-to-event outcomes, the illustration would express total events; for other outcomes, it would express participants per arm. These are planning assumptions, not a description of the trial’s own design or an observed power result. The registry record does not report a sample-size justification for the study, and no planning estimates should be interpreted as the number actually analyzed.

The posted material does not give the observed effect needed to evaluate such an illustration for this primary endpoint. It also does not provide a primary outcome analysis. A planning calculation cannot replace the missing outcome estimate, confidence interval, or test result. Nor does a planned sample size demonstrate that the study had adequate precision for its actual endpoint.

Finally, a statistical comparison would need to be interpreted in light of the group formation and analysis population. Allocation is not stated, and the record cautions that the arms are not a like-for-like control comparison. Statistical adjustment, even if it had been reported, would not necessarily remove unmeasured differences. The available registry record supports an explanation of the intended endpoint and general statistical concepts, but not an independent reconstruction of the study’s analysis.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures, but does not give enough detail to establish how they were ordered or how analyses across them were handled. It identifies visual-distortion symptoms as the primary endpoint, yet reports 0 analyses. The statistical plan, including any prespecified multiplicity procedure, is not reported in the registry record. When several outcomes or comparisons are examined, multiplicity can increase the chance of at least one apparently unusual result; methods such as a prespecified hierarchy or adjustment can address that issue in defined settings. No such method can be attributed to this study from the available record.

The record also does not report a missing-data strategy for the primary endpoint. It notes one exclusion from the toric-IOL primary endpoint population because an improper method was used to simulate visual distortion. This is a specific protocol-deviation note, but it does not explain how other absent, incomplete, or unusable ratings were handled. The primary endpoint denominators by group are not reported in the registry record.

The adverse-event counts at risk should not be used as the endpoint analysis denominators. They are recorded in the safety information, and the endpoint description separately identifies an exclusion. The record does not state whether all enrolled participants completed the self-assessment or how the analysis population was defined beyond that exclusion.

These omissions matter because the analysis population and missing-data approach can affect both the estimated mean and its uncertainty. Without participant-level accounting, endpoint denominators, and analysis rules, readers cannot determine whether the reported outcome—if available—would represent all enrolled participants, those with usable assessments, or another population. No such analysis result is posted in the registry record.

11. 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.

Most frequent non-serious adverse event terms

The safety record lists 45 participants at risk in the toric-IOL group and 34 in the non-toric-IOL group. It reports 0 serious adverse events in each group. For other adverse events, it reports 0 in the toric-IOL group and 2 in the non-toric-IOL group. These are the event counts recorded in the registry; they do not provide detail about event types, timing, severity beyond the serious-versus-other classification, or attribution.

Deaths are not reported in the registry record. The absence of a death count is not evidence that no deaths occurred. The record also provides no serious adverse-event terms, so the types of serious events are not described.

These safety counts are descriptive. They do not establish a comparative risk because the record does not report an inferential safety analysis, and it cautions that the arms are not a like-for-like control comparison. The group counts at risk are specific to the safety record and should not be treated as the denominators for the primary symptom endpoint. The registry record does not state whether safety events were collected over the same observation period for both groups.

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

The result that can be described from the registry record is the intended measurement: a baseline patient rating of visual-distortion symptoms, coded from 0 to 3, with lower values representing the best outcome. The record also identifies participants with toric and non-toric IOLs as the comparison groups and notes a protocol-deviation exclusion in the toric-IOL group’s primary endpoint population.

The posted results do not report the primary endpoint values. Without group means, standard deviations, category distributions, or an analysis, readers cannot tell what symptom ratings participants gave or whether the groups differed. The record also does not report a confidence interval or p-value. It therefore does not establish the magnitude or precision of any group contrast.

Even a numerical difference between these groups would not, on its own, show that lens type caused that difference. The registry says allocation was not stated and cautions that the arms are not a like-for-like control comparison. Differences in group composition or other factors could be relevant, but the available information does not permit those factors to be assessed. The record does not report an adjusted analysis or the information needed to reconstruct one.

The endpoint is a subjective baseline rating, not a reported measure of change over time. It cannot by itself show whether symptoms improved or worsened after an intervention. The listed self-assessment is the measurement procedure; the record does not describe a randomized treatment assignment or report follow-up outcome results.

Accordingly, the record identifies a clinically interpretable symptom question but does not answer it quantitatively. It does not support a claim that one group had better or worse symptom ratings, that a difference was statistically significant, or that either lens type caused a particular symptom outcome. Those conclusions would require outcome data and analysis details that are not reported in the registry record.

13. Why This Trial Matters Statistically

This study is statistically notable for the gap between a clearly defined patient-reported endpoint and the absence of posted endpoint results. The scale is described in plain categories, its numerical range is specified, and its direction is stated. Yet the registry record gives no group summaries or analysis. This makes the distinction between an outcome definition and an outcome finding especially important: knowing what was measured does not reveal what participants reported.

The record also illustrates why a group comparison needs more than two group labels. It explicitly states that allocation was not reported and that the arms are not a like-for-like control comparison. In that setting, a statistical contrast would describe observed group differences but would not automatically identify a causal effect. Design information and analysis details are needed to judge whether a comparison is interpretable.

The endpoint itself raises a useful measurement question. The ratings are ordered categories, while the specified summary is a mean and standard deviation. As a general matter, readers benefit from knowing whether the numerical summary reflects the response distribution and from seeing category-level information when available. Here, the registry does not report such results, so neither the average level nor the pattern of responses can be examined.

The record’s explicit note about excluding one toric-IOL participant for a protocol deviation also highlights the importance of transparent analysis populations. A single documented exclusion does not explain all data handling. Endpoint denominators, missing-data rules, and the full analysis population remain unreported.

These features make the record useful for understanding the intended question and the limits of registry-based interpretation. Its statistical significance lies less in a reported estimate than in the need to separate endpoint specification, study design, analysis, and evidence. The available record documents the first of these more clearly than the others.

14. 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 that the registry record reports no primary outcome results. It gives no mean, standard deviation, response distribution, confidence interval, or test for visual-distortion symptoms. Consequently, neither the level of symptoms nor a group contrast can be evaluated from the posted results.

The comparison design is also insufficiently described for causal interpretation. Allocation is not stated, and the registry itself warns that the arms are not a like-for-like control comparison. The record does not report how participants entered each group, whether groups were comparable at baseline, or whether an adjusted analysis was conducted. These details are not reported in the registry record.

The endpoint is a subjective rating with ordered categories numerically coded from 0 to 3. The registry specifies a mean and standard deviation but provides no category counts or distributional information. As a result, readers cannot see whether ratings were concentrated in particular categories or determine how well the mean represents the response pattern.

The primary endpoint description notes an exclusion in the toric-IOL group for a protocol deviation involving the simulation method. It does not provide a complete accounting of the analysis population, endpoint denominators, other exclusions, missing assessments, or missing-data handling. Multiplicity procedures and the statistical analysis plan are also not reported in the registry record.

Safety information is limited to event counts and at-risk group counts. Event descriptions and deaths are not reported in the registry record, and the counts do not constitute a comparative safety analysis. The record’s planning assumptions do not fill these gaps: they are described as an illustration based on an observed effect, while the endpoint result needed to interpret such planning is not posted.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Patient Perception of Visual Distortions — NCT02203747.
• Registry record last updated 2015-12-22; status last verified 2015-09.
• Results first posted 2015-12-22.
• 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.

18. Record Summary

NCT02203747 is a completed study titled “Patient Perception of Visual Distortions,” sponsored by Abbott Medical Optics. The registry lists enrollment of 79, with a start date of 2014-08 and primary completion in 2014-10. Cataract and astigmatism are listed as conditions.

The stated purpose is to evaluate visual distortions reported by pseudophakic patients. The intervention is administration of patient self-assessment. The two described groups comprise participants bilaterally implanted with toric IOLs and participants bilaterally implanted with non-toric IOLs. Allocation is not stated, and the registry cautions that the arms are not a like-for-like control comparison.

The primary endpoint is a baseline rating of visual-distortion symptoms on a scale from 0 to 3, summarized as a mean with standard deviation; lower values represent the best outcome. One participant in the toric-IOL group was excluded from the primary endpoint population because of a protocol deviation. The registry lists 2 outcome measures and 0 analyses. Primary endpoint results and analysis details are not reported in the registry record.