Safety and Effectiveness of Wavefront-Guided LASIK Correction of Hyperopic Refractive Errors: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Safety and Effectiveness of Wavefront-Guided LASIK Correction of Hyperopic Refractive Errors (NCT01675479), a na na study. The primary outcome is Number of Eyes With a Loss of >2 Lines for Best Spectacle Corrected Visual Acuity (BSCVA).

2. Clinical Question

In plain terms, the study asks whether eyes treated with the specified wavefront-guided procedure experienced a substantial decline in best spectacle corrected visual acuity after surgery. The endpoint is a safety measure: it focuses on loss of visual acuity relative to the best spectacle-corrected reference, rather than on the change in uncorrected vision alone. The registry also lists uncorrected visual acuity of 20/40 or better as a secondary outcome, but does not report its result.

Because the record describes only one group, the study can describe outcomes among those treated if results are available, but it cannot establish a treatment contrast against an untreated or alternative-treatment group. The primary endpoint result is not reported in the registry record, so the stated hypothesis cannot be evaluated from the posted results.

3. Trial Design

This was a prospective study with a single-group design. The registry record lists the study as completed and gives an enrollment of 167. It identifies hyperopia as the condition and wavefront-guided LASIK correction of hyperopic refractive errors as the intervention. The study is titled as an evaluation of safety and effectiveness using the iDesign Advanced Wavescan Studio system and Star S4 IR excimer laser system.

The registry lists allocation as NA and masking as NONE. There is no comparator arm described, so the design is not a randomized comparison. The recorded arm is wavefront-guided LASIK. These details mean that any reported outcomes would describe the treated group, rather than estimate a difference between treatment groups. The reason for the design choices is not reported in the registry record.

The record gives a start date of 2012-12-31 and a primary completion date of 2016-10-31. The primary endpoint timeframe is listed as 12 Months. Its description refers to the occurrence of a loss of more than two lines at any postoperative visit, measured with ETDRS logMAR visual acuity charts at 4 meters. The registry wording does not clarify how the “any postoperative visit” wording relates to the listed 12 Months timeframe.

The planned sample-size justification, eligibility criteria, detailed visit schedule, and statistical analysis plan are not reported in the registry record. The study record lists two outcome measures and no analysis entries. The registry also contains planning assumptions for illustrative sample-size calculations based on an observed effect, but those assumptions do not describe the trial's own design: they specify a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. Since this study is recorded as single-group, those illustrative two-arm assumptions should not be mistaken for the actual trial design or for observed trial results.

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: 167 subjects were consented in the study, of which 69 subjects had one or both eyes treated for a total of 135 treated eyes.

Overall Study

Reasons for not completing this period:

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Number of Eyes With a Loss of >2 Lines for Best Spectacle Corrected Visual Acuity (BSCVA), measured over 12 Months.

The primary endpoint counts eyes with a loss of more than two lines for best spectacle corrected visual acuity (BSCVA). BSCVA represents visual acuity measured with spectacle correction; the endpoint therefore focuses on a decline despite correction, rather than simply whether uncorrected vision meets a particular threshold. The record specifies ETDRS logMAR visual acuity charts at 4 meters as the measurement method.

A threshold-based endpoint turns a measured change into an event classification: an eye either meets the specified loss criterion or does not. Counting such events can make a safety concern easier to describe than reporting only an average change, because an average can obscure a smaller number of larger declines. This is a general statistical rationale, not a finding about this study.

The registry states the hypothesis that fewer than 5% of eyes would have a loss of more than two lines at any postoperative visit. It lists the endpoint timeframe as 12 Months. The primary endpoint result, the number of eyes assessed, and the analysis denominator are not reported in the registry record. Without those details, it is not possible to determine whether the stated hypothesis was met or to judge the precision of an estimate. The secondary outcome, uncorrected visual acuity of 20/40 or better, is also named, but its result is not reported in the registry record.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The registry record identifies a count endpoint: the number of eyes meeting a specified visual-acuity loss criterion. A count endpoint tallies qualifying units. In this study the unit is an eye, and the qualifying criterion is a loss of more than two lines for BSCVA. The record does not report the observed count, the number of eyes assessed, or a rate based on those quantities. No calculation of an observed frequency or its uncertainty is therefore possible from the registry record.

What does a confidence interval add?

In general, a confidence interval expresses the uncertainty around an estimate under a statistical model. It gives a range of values compatible with the data and model at a stated confidence level. A narrow interval indicates greater precision than a wide interval, while neither guarantees that the estimate is free from bias. For an event count, the interval depends on both the observed count and the number of units assessed. Neither the primary count nor its denominator is reported in the registry record, and no confidence interval is posted.

The hypothesis in the endpoint description is framed as a threshold for the proportion of eyes with a specified loss. A complete statistical assessment would need to relate an observed event count to the set of eyes analyzed, and would need an uncertainty measure or a specified hypothesis test to show how compatible the data are with the threshold. The registry does not report the endpoint result or the analysis method. It is therefore not possible to reconstruct that assessment or state whether the data support or contradict the hypothesis.

Why can eye-level data need special handling?

General statistical methods often assume that each analyzed observation contributes independent information. If both eyes from a participant are included, their outcomes may be related because they share characteristics and care experiences. Methods that account for within-participant correlation can be important in that setting. The registry record gives participant enrollment and describes an eye-level endpoint, but does not say whether one or both eyes per participant were analyzed or whether any correlation adjustment was used. No particular method should be attributed to this study.

What does the single-group design imply?

In a randomized comparison, a between-group contrast can estimate how outcomes differ under the assigned study conditions, subject to the study's assumptions and conduct. Here, the registry describes a single group and no comparator. A result for the treated group, if reported, would be a descriptive outcome for that group. It would not by itself distinguish the procedure's effect from changes over time, participant characteristics, measurement conditions, or other influences. This is a general interpretation of uncontrolled designs, not a claim about what caused any individual outcome in this study.

Allocation is listed as NA and masking as NONE. The record does not report an analysis plan explaining how these design features were handled. The term “prospective” in the study title describes the study's stated orientation, but does not supply the missing details of outcome ascertainment, analysis populations, or statistical models.

How should sample-size illustrations be read?

The registry's sample-size assumptions describe planning illustrations computed from an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The stated effect to detect is a fraction of the observed effect. These are assumptions for illustrative calculations, not evidence that the study itself used a two-arm design or those assumptions. The trial is listed as single-group, and its sample-size justification is not reported in the registry record. The observed effect value and numerical illustration results are also not reported in the registry record.

A sample-size calculation estimates how many participants per arm a hypothetical design might require under specified assumptions. It is not the same as observed power, which is not a useful substitute for examining the estimate and its uncertainty after a study. Planning illustrations can change substantially when the assumed effect, variability, event rate, allocation, or analysis method changes. Those considerations are general; the registry record does not state a protocol sample-size calculation for this trial.

What analysis details remain unavailable?

The registry lists no analysis entries. The analysis population, handling of missing acuity assessments, method for defining the baseline reference, and approach to repeated postoperative measurements are not reported in the registry record. Since the endpoint description refers to loss at any postoperative visit while the timeframe is listed as 12 Months, the record also leaves unclear how repeated measurements contributed to the endpoint. These omissions prevent reproduction of an endpoint estimate, even if a result were otherwise available.

The registry names the visual-acuity measurement instrument and distance, which helps define how acuity was assessed. It does not give measurement-level data, a statistical model, a testing procedure, an interval estimate, or a prespecified method for handling multiple outcomes. General statistical interpretation depends on those features, but no specific method can be inferred from the record.

10. Multiplicity, Missing Data and Analysis Populations

The registry lists two outcome measures: the primary count of eyes with a loss of more than two lines for BSCVA, and a secondary outcome concerning uncorrected visual acuity of 20/40 or better. It does not report the results for either outcome. The analysis plan and any strategy for handling multiple outcomes or repeated assessments are not reported in the registry record.

Multiplicity is a general statistical issue that arises when several hypotheses or outcomes are examined. If many tests are conducted, the chance of at least one apparently unusual result can increase unless the analysis accounts for the number and structure of those tests. This does not mean a result is invalid; it means that interpretation depends on what was prespecified and how the analyses were conducted. The registry record does not describe a multiplicity adjustment, hierarchical testing plan, or other approach, so none should be assumed.

Missing data also affect interpretation. The record does not report how many eyes had measurements at each visit, how missing visual-acuity assessments were handled, or whether the analysis included all enrolled participants, a subset, or another defined population. A missing result is not equivalent to an outcome of no loss. Without the analysis denominator and missing-data approach, the extent to which the endpoint represents the enrolled group cannot be assessed.

The participant enrollment figure and eye-based endpoint refer to different units. The registry does not report which eyes were included, whether participants could contribute more than one eye, or how any within-participant dependence was handled. Nor does it report an analysis population definition. These omissions limit both reproducibility and assessment of uncertainty. The record's absence of analysis entries means that the statistical handling of multiplicity, missing observations, and analysis populations is not documented in the posted record.

11. 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 serious adverse event terms

Serious events with the highest arm-level rate: epithelial ingrowth requiring non refractive intervention (1.4%), decrease in bscva (1.4%), cataract (1.4%), severe glare (1.4%).

For the wavefront-guided LASIK group, the registry record lists 69 at risk and 3 affected for serious adverse events. It lists 0 other adverse events and 0 deaths. These are the figures recorded for the group; the registry does not provide further detail in the listed counts about event timing, severity definitions, or attribution to the procedure.

The record also lists four serious-event terms, each with a reported percentage of 1.4%: epithelial ingrowth requiring non refractive intervention, decrease in BSCVA, cataract, and severe glare. These term-level entries should be read as separate reported terms. The registry does not report enough information to determine whether the terms overlap within affected individuals, how the percentages were calculated, or whether an event was judged related to the intervention. They should not be added together or interpreted as a total risk.

Safety counts and percentages describe the entries in the registry; they do not, on their own, establish causation or provide a comparison with another treatment. The study has no comparator group recorded, and the serious-event figures do not replace the missing primary visual-acuity endpoint result. The registry record also does not report additional detail needed to assess the duration of safety follow-up or the completeness of event reporting.

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

The record describes a prospective, single-group study evaluating wavefront-guided LASIK for hyperopic refractive errors. It identifies a primary safety endpoint based on loss of more than two lines in BSCVA and states a hypothesis of fewer than 5% of eyes meeting that criterion at any postoperative visit. Those details clarify what the investigators intended to assess, but the primary endpoint result is not reported in the registry record.

Without the observed number of eyes, the number assessed, and an uncertainty estimate, the posted information cannot establish how often the endpoint occurred or how precisely it was estimated. It also cannot show whether the stated hypothesis was met. The secondary visual-acuity outcome is listed, but its result is not reported either. The absence of these results should not be read as evidence that no qualifying outcome occurred.

The design also constrains interpretation. Because the registry records a single group and no comparator, it cannot provide a controlled estimate of how outcomes differ from another procedure or from no intervention. This does not prevent descriptive reporting of outcomes in the treated group, but it limits causal conclusions that could be drawn even if those results were available.

The serious adverse event figures are separately reported: 3 affected among 69 at risk, with 0 other adverse events and 0 deaths. The registry lists several serious-event terms at 1.4% each. These figures are useful as entries in the safety record, but the record does not explain attribution, overlap among terms, or the calculation details for the percentages. They should not be treated as a comparison or as proof of cause.

In statistical terms, the study record gives a question, an endpoint definition, and limited safety counts, but not the outcome evidence needed to estimate the primary endpoint. The enrollment figure alone cannot fill that gap. Nor can planning illustrations substitute for observed outcomes. A careful interpretation therefore distinguishes what was planned and recorded from what the posted results actually establish.

13. Why This Trial Matters Statistically

This study illustrates why a clearly named clinical endpoint is not enough for statistical interpretation. The record defines a specific visual-acuity loss criterion, gives its measurement method, and states a threshold-based hypothesis. Those features make the intended question understandable. Yet without the observed count and denominator, there is no endpoint estimate to interpret and no way to quantify its precision.

It also highlights the importance of matching the unit of analysis to the unit of enrollment. Enrollment is reported in participants, while the primary outcome counts eyes. In eye studies, the analysis needs to make clear which eyes contributed and whether multiple eyes from one participant were handled as related observations. The registry record does not provide those details. This is a general reporting lesson, not a conclusion about the study's underlying analysis.

The single-group design is another important statistical feature. A one-group outcome can be informative as a description of the treated group, but it does not create a randomized comparison. Readers should distinguish an observed outcome in a treatment group from an estimate of a treatment effect relative to a control. This distinction is especially important when a study title or summary uses terms such as “safety and effectiveness.”

Finally, the registry contains safety entries and planning assumptions, but those have different roles. Safety counts describe reported events; sample-size illustrations describe hypothetical planning under specified assumptions. Neither replaces a complete endpoint analysis. The record demonstrates why transparent reporting of denominators, analysis populations, missing-data handling, estimates, and uncertainty is central to making a clinical study statistically interpretable.

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.

Several limitations specific to this record constrain interpretation. Most importantly, the registry does not report the primary endpoint result. It provides no observed count of eyes with the specified BSCVA loss, no number of eyes analyzed, and no uncertainty estimate. The secondary outcome result is also not reported. The stated endpoint hypothesis therefore cannot be judged from the posted results.

The study is recorded as single-group, with allocation listed as NA and masking as NONE. No comparator is described, so there is no randomized between-group contrast in the record. Any descriptive outcome, if reported, would not by itself establish a causal difference from another treatment or condition.

The enrollment figure is in participants, but the primary endpoint is in eyes. The record does not report whether one or both eyes per participant were included, how the analysis handled related eye measurements, or which analysis population was used. It also does not describe missing-data handling, the baseline reference for change, or the statistical method for combining measurements across postoperative visits.

The primary endpoint timeframe is listed as 12 Months, while its description refers to a loss at any postoperative visit. The record does not clarify how those statements fit together. Although the endpoint measurement method is named, other details needed to reproduce the analysis are not reported in the registry record. These limitations concern what the registry documents; they do not establish that the underlying study lacked additional procedures or analyses.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Safety and Effectiveness of Wavefront-Guided LASIK Correction of Hyperopic Refractive Errors — NCT01675479.
• Registry record last updated 2021-12-15; status last verified 2021-12.
• Results first posted 2018-04-25.
• 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.

18. Record Summary

The registry record identifies NCT01675479 as a completed prospective study of wavefront-guided LASIK correction of hyperopic refractive errors. It lists Abbott Medical Optics as the sponsor, an enrollment of 167, and a single-group design with no masking. The primary endpoint is the number of eyes with a loss of more than two lines for BSCVA, with a listed timeframe of 12 Months and a stated hypothesis of fewer than 5% experiencing that loss.

The record lists uncorrected visual acuity of 20/40 or better as a secondary outcome. It reports serious adverse event figures of 3 affected among 69 at risk, 0 other adverse events, and 0 deaths, along with four serious-event terms at 1.4% each. The primary and secondary outcome results, analysis population, and statistical analysis details are not reported in the registry record.