Early Experience With Descemet's Stripping Automated Endothelial Keratoplasty: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Early Experience With Descemet's Stripping Automated Endothelial Keratoplasty (NCT00744796), a registered phase not stated study. The primary outcome is Best Spectacle Corrected Visual Acuity (BSCVA).

2. Clinical Question

The clinical question is descriptive rather than comparative on the information recorded. It concerns the observed visual acuity assessment after DSAEK and the intended relationship of clinical findings to imaging. Without a control group, the record cannot establish how outcomes would compare with another procedure or with the course of the condition without DSAEK. The registry record does not report a specific imaging endpoint result, a correlation estimate, or a statistical analysis of the relationship between imaging and visual acuity. Thus, the stated aim and the available outcome description should be distinguished from results: the former explains what the investigators intended to examine, while the latter would require participant-level or summary findings that are not reported in the registry record.

3. Trial Design

The registry record describes a completed study sponsored by the University of Texas Southwestern Medical Center. The recorded start is 2006-12, primary completion is 2008-07, and enrollment is 21. Its title and summary characterize the work as an early clinical-outcomes and diagnostic-imaging investigation of Descemet's Stripping Automated Endothelial Keratoplasty (DSAEK) for corneal edema secondary to corneal endothelial cell dysfunction.

One arm is listed: DSAEK outcomes in patients with corneal edema. The arm description states that best spectacle corrected visual acuity and anterior segment optical coherence tomography (OCT) would be performed at minimum in patients who had undergone DSAEK. The intervention list includes DSAEK as a procedure, and OCT and best spectacle corrected visual acuity (BSCVA) as diagnostic tests. These entries describe both the procedure and assessments; they do not constitute separate treatment arms.

The record does not describe a randomized comparison. Allocation is not stated, and the listed information does not identify a concurrent control arm. Accordingly, the results, if reported, would be interpreted as observations among treated participants rather than as a contrast between assigned groups. A treatment effect relative to a comparator cannot be estimated from the listed design alone.

The primary outcome is BSCVA, measured in participants at 6-9 months Post-Operative. Three outcome measures are listed, but their names and numerical results beyond the primary outcome description are not available in the registry record. No statistical analyses are listed. The record does not report the protocol details, enrollment criteria, follow-up completeness, analysis population definition beyond the statement that participants for analysis were determined per protocol, or a prespecified statistical plan. These omissions limit reconstruction of how the intended study design was carried out.

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.

Pre-operative

Post-Operative Day 1

Post-Operative 3-6 Months

Post-Operative 6-9 Months

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: The number of participant, for analysis, were determined per protocol.

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 Best Spectacle Corrected Visual Acuity (BSCVA), measured over 6-9 months Post-Operative.

The primary endpoint is best spectacle corrected visual acuity (BSCVA), recorded as a count of participants at 6-9 months Post-Operative. The endpoint description says visual acuity was determined using detection of hand motion, counting of displayed fingers, and accuracy of Snellen chart reading at specified distances. These descriptions indicate that assessment could include different levels or forms of visual acuity testing, rather than one continuous numerical measure as described in the registry record.

Visual acuity is used in a corneal outcomes study because it describes a functional aspect of vision after the procedure. The registry record frames BSCVA as the primary outcome and separately describes anterior segment OCT as an imaging assessment. The purpose summary says clinical data were to be correlated with imaging modalities, but does not define a specific imaging variable or report a correlation result.

The endpoint's unit is participants, and its parameter is a count of participants. However, the registry record does not give the number of participants meeting any visual acuity category, the categories used for the count, or a numerical summary of BSCVA. It therefore does not permit a reader to determine the observed distribution of visual acuity results from the primary endpoint entry alone. The registry record also does not explain how hand-motion detection, finger counting, and Snellen chart accuracy were combined or classified for analysis. Such operational details matter because endpoint interpretation depends on the categories and rules used to convert assessments into reported counts.

In general, a clearly defined endpoint helps readers connect the clinical question to the outcome measurement. Here, the description identifies the assessment methods and follow-up timeframe, but the absent endpoint results and classification details prevent evaluation of the magnitude and precision of the observed outcome.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the primary measure represent?

The endpoint is a participant count for BSCVA, assessed at 6-9 months Post-Operative. Its description refers to hand-motion detection, counting displayed fingers, and Snellen chart reading at specified distances. The registry record does not state how these assessment findings were converted into the count, which result categories were used, or the number of participants in each category. Without those details and the results, a reader cannot reconstruct the endpoint distribution.

General statistical explanation: a count records how many observations fall into a defined category or set of categories. Its meaning depends on the category definitions, the population included in the analysis, and whether each participant contributes one observation. Those operational rules are not reported in the registry record. The entry says the analysis participants were determined per protocol, but does not define that population further.

What can a confidence interval tell a reader?

General statistical explanation: a confidence interval gives a range of values compatible with the observed data under a specified statistical method. Its width conveys precision: a wider interval indicates less precise estimation, while a narrower interval indicates greater precision under that method. A confidence interval does not remove limitations in study design, measurement, or selection of the analysis population. The registry record does not report a confidence interval for BSCVA or for an imaging relationship, so neither the estimate nor its precision can be evaluated from the record.

What does the absence of a comparator mean?

The registry record lists a DSAEK group and does not state an allocation method or identify a control group. General statistical explanation: a comparative treatment estimate requires a contrast between groups or conditions. In an uncontrolled group, a measured outcome can describe what was recorded among participants, but it cannot on its own estimate what would have happened to comparable participants under a different treatment or no procedure. Differences in participant characteristics, clinical course, and measurement may also influence observed outcomes. These are general interpretation issues rather than claims about events in this study.

The study's purpose includes correlating clinical outcomes with anterior segment imaging. General statistical explanation: a correlation describes how two measured variables vary together; it does not by itself establish that one caused the other. Interpreting such an estimate requires information about the variables, analysis population, missing observations, and method. No correlation estimate or method is reported in the registry record.

How should planning calculations be read?

The sample-size assumptions describe a planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The illustration defines the effect to detect as a stated fraction of the observed effect. For time-to-event calculations, the stated convention is a total number of events; for other calculations, it is participants per arm. These are assumptions for planning illustrations, not details of this study's design or evidence of observed power. In particular, the registry record lists one DSAEK group and does not describe equal allocation between two study arms.

General statistical explanation: sample-size planning asks how much information might be needed to detect a specified effect under chosen assumptions. The answer changes when the assumed effect, variability, event frequency, significance level, allocation, or statistical method changes. Calculations based on an observed effect use that effect as an input for an illustration; they do not show that the study was planned prospectively to detect it. Power is a design quantity tied to assumptions, not a retrospective measure of whether a completed study found a result. No sample-size justification or protocol-based power calculation is reported in the registry record.

Why does over-dispersion matter in general?

General statistical explanation: over-dispersion occurs when count data vary more than a chosen model expects. If the model understates that variation, standard errors can be too small and uncertainty can appear lower than it is. Analysts may use a model that accommodates extra variation when the data and design warrant it. The registry record does not report a dispersion estimate, a count model, or any analysis of over-dispersion. The primary endpoint is described as a count of participants, but that alone does not establish that an over-dispersion model is relevant or was used.

More broadly, a statistical method cannot be inferred solely from an endpoint label. The registry record lists 0 analyses and does not provide an analysis plan, model specification, significance tests, or uncertainty estimates. Any methodological interpretation beyond the stated planning assumptions would therefore be speculative. The information permits explanation of general statistical concepts, but not attribution of a particular inferential method to the investigators.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists 3 outcome measures but does not enumerate their names in the available information beyond the primary BSCVA outcome. It records 0 analyses and does not describe a testing hierarchy, a prespecified primary-versus-secondary analysis strategy, or any multiplicity adjustment. These details are not reported in the registry record.

General statistical explanation: when several outcomes or hypotheses are tested, the chance of at least one apparently notable result can increase if each is assessed separately. A prespecified hierarchy or an adjustment can help control that issue, but the appropriate approach depends on the scientific question and analysis plan. No approach can be attributed to this study from the registry record. The number of outcomes alone does not show that multiple hypothesis tests were performed.

The record does not report the number of participants contributing data to the primary endpoint, the number with missing BSCVA assessments, or how missing observations were handled. Although enrollment is 21 and the endpoint population is described as determined per protocol, enrollment does not establish that every participant contributed an endpoint observation. The record also does not define the per-protocol population or state whether exclusions occurred.

General statistical explanation: missing data can affect both the amount of information available and the interpretation of an estimate, particularly when the reasons for missingness relate to outcomes or participant characteristics. An analysis should explain who was included, what was missing, and what assumptions or methods were used. Those details are not reported in the registry record. No inference about completeness of follow-up or the handling of missing observations can be made from the enrollment count alone.

Because the registry record gives neither analysis details nor endpoint results, it is not possible to assess multiplicity, reproduce an analysis, or determine how the reported analysis population differed from enrollment.

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 0% reporting threshold.

The DSAEK Group lists 21 participants at risk for serious adverse events and 0 affected. It also lists 21 at risk for other adverse events and 0 affected, with 0 deaths. These are the safety counts recorded for the group. No serious adverse event terms are listed.

These figures should be read as counts in the registry record, not as proof that no adverse events occurred under every definition or at every time. The record does not provide event definitions, collection procedures, observation windows for safety, or detail about how events were attributed. It also does not report whether participants contributed safety information for the same period as the primary endpoint. The phrase “at risk” describes the recorded denominator; it should not be taken as evidence that all participants had identical follow-up or complete event ascertainment.

General statistical explanation: when no events are recorded in a group, the observed count is zero, but a zero count does not establish that the underlying event probability is zero. Precision depends on the amount and quality of follow-up and on the event definition and ascertainment process. No confidence interval or other uncertainty estimate is reported for these safety counts. Therefore, the counts are useful as a concise registry description but do not, by themselves, characterize the full safety profile or support a comparative safety conclusion.

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

The registry record identifies a completed, small enrolled cohort focused on early outcomes after DSAEK for corneal edema secondary to corneal endothelial cell dysfunction. Its stated primary measure is BSCVA at 6-9 months Post-Operative, with assessment described through hand-motion detection, finger counting, and Snellen chart reading. OCT is listed as an additional diagnostic assessment, and the stated purpose includes relating clinical outcomes to imaging.

What the record does not provide is essential to interpreting results: no numerical BSCVA outcome, category distribution, imaging result, correlation estimate, confidence interval, or statistical test is reported. It is therefore not possible to describe the direction, magnitude, or precision of the clinical findings from the registry record. The absence of reported results should not be mistaken for a result showing no change or no association.

The study is not described as a randomized or controlled comparison. The record lists one DSAEK group and does not state allocation. Consequently, even a descriptive post-procedure outcome would not establish a causal effect relative to a control condition. General clinical and statistical reasoning requires a suitable comparison to distinguish outcomes associated with an intervention from outcomes that might occur for other reasons; the registry entry does not provide such a comparison.

The safety entries report 0 serious events, 0 other events, and 0 deaths among 21 participants listed at risk in the respective categories. These counts are limited to what the registry record reports and do not characterize event definitions, ascertainment, or uncertainty. Likewise, the sample-size assumptions are planning illustrations and are not observed power or evidence of the original study's design rationale.

The record is useful for identifying the study's clinical aim, assessments, enrollment, sponsor, and recorded status. It does not furnish enough outcome or analysis information to judge the measured visual acuity distribution, the relationship between imaging and clinical outcomes, or comparative treatment effects.

13. Why This Trial Matters Statistically

Statistically, this study illustrates the distinction between an explicitly stated clinical question and the information needed to answer it quantitatively. The record identifies a population with corneal edema secondary to corneal endothelial cell dysfunction, a procedure of interest, a BSCVA primary outcome, a follow-up timeframe, and imaging assessments. These elements help define what investigators intended to describe.

Yet interpretation also depends on reported results and methods. The registry record does not provide the primary outcome count, the imaging findings, an association estimate, or inferential analyses. It also does not define the outcome categories or the analysis population beyond the statement that participants were determined per protocol. Without these details, a reader cannot assess the outcome distribution, precision, missingness, or reproducibility.

The design information matters as well. A single listed group without a stated comparator supports a descriptive question, not a controlled estimate of differences between treatment strategies. This distinction is especially important when the study title and summary emphasize early clinical outcomes: observed outcomes after a procedure and effects attributable to that procedure are different statistical claims.

The record also provides a useful caution about interpreting planning illustrations. Assumptions involving equal allocation between two arms and a normal approximation are stated for the illustration, while the study record lists one DSAEK group. Planning calculations should not be mistaken for the actual design or for observed power.

Finally, the recorded zero adverse-event counts are meaningful as registry entries but are not a complete statistical safety assessment without event definitions, follow-up detail, and uncertainty estimates. Taken together, these points show why study design, measurement, analysis, and transparent reporting all matter alongside the clinical topic.

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 registry record is limited in detail about participant selection. It names the condition and states that 21 participants were enrolled, but eligibility criteria and recruitment methods are not reported in the registry record. The analyzed population is said to be determined per protocol, yet the protocol definition, exclusions, and number included in the primary analysis are not stated.

The outcome description identifies BSCVA at 6-9 months Post-Operative and gives examples of assessment methods, but does not define the result categories or explain how the methods were combined. The numerical primary outcome is not reported in the registry record. The other listed outcome measures, imaging findings, and any relation between imaging and clinical outcomes are also not described in enough detail to interpret.

The absence of a stated comparator and allocation method prevents a controlled comparison. The record does not report whether other groups existed outside the listed registry arm. Any causal interpretation would therefore go beyond the information recorded. This is a limitation of what can be inferred from the registry entry, not a claim about unreported study activity.

Methods for analysis, handling of missing assessments, multiplicity, and uncertainty are not reported in the registry record. The recorded analysis count is 0, and there are no reported statistical estimates with which to assess precision or reproduce an analysis. Protocol details, sample-size justification, and interim analyses are also not reported in the registry record.

Safety interpretation is constrained by the lack of event definitions, collection procedures, and follow-up detail. The recorded zero counts do not supply an uncertainty estimate or establish complete event capture. These reporting gaps make the available description useful for identifying the study's focus, but insufficient for a comprehensive statistical appraisal of outcomes or safety.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Early Experience With Descemet's Stripping Automated Endothelial Keratoplasty — NCT00744796.
• Registry record last updated 2020-12-11; status last verified 2020-11.
• Results first posted 2020-12-11.
• 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

NCT00744796 is a completed study titled “Early Experience With Descemet's Stripping Automated Endothelial Keratoplasty.” It was sponsored by the University of Texas Southwestern Medical Center, with recorded start 2006-12, primary completion 2008-07, and enrollment of 21 participants.

The study concerns DSAEK for corneal edema secondary to corneal endothelial cell dysfunction. BSCVA is the primary outcome, described as a participant count assessed at 6-9 months Post-Operative; anterior segment OCT is also listed. The registry record does not report the numerical primary outcome or an imaging analysis result. One DSAEK group is listed, with no stated comparator or allocation method. The safety entries record 0 serious events, 0 other events, and 0 deaths among 21 participants at risk in each listed category. The record lists 3 outcome measures and 0 analyses.