This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Evaluation of Deposits on Contact Lenses Worn Extended Wear (NCT00725530), a randomized na study. The primary outcome is Front Surface Lens Deposits.
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT00725530 |
| Phase | NA |
| Condition | Myopia |
| Allocation | Randomized |
| Design model | Crossover |
| Masking | Single |
| Enrollment | 54 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Alcon Research |
| Results posted | Yes |
2. Clinical Question
Population
The primary outcome population is described as all enrolled participants. The registry lists myopia as the condition and reports enrollment of 54 participants. It does not report how many participants completed each lens-wear period or contributed to each outcome assessment.
Intervention
One sequence began with balafilcon A contact lenses, identified as PureVision, followed by etafilcon A contact lenses, identified as Acuvue2. Each product was worn bilaterally on an extended-wear, overnight basis for 7 days. The primary measure concerns deposits on the front surface after lens wear.
Comparator
The alternative sequence began with etafilcon A and then used balafilcon A. The comparison is therefore framed within a crossover design, in which participants were assigned to an order of product use. The registry record does not report participant-level outcome values or a direct product comparison.
Primary question
The clinical question is how front-surface lens deposits were classified after each product was worn, and whether the posted results allow those classifications to be compared. The registry defines deposit thresholds and an assessment procedure, but does not report the resulting counts or an analysis. The relative deposit findings are therefore not reported in the registry record.
3. Trial Design
This was a randomized, single-masked crossover study, with the two product sequences described as balafilcon A followed by etafilcon A, or etafilcon A followed by balafilcon A. In a crossover design, the same participant can receive each intervention in sequence, so comparisons may use within-participant information rather than treating each product group as entirely separate. The registry record does not specify which parties were masked.
The enrolled population was described as participants with myopia. Enrollment was 54. The primary outcome population is stated as all enrolled participants, but the record does not give the number assessed at each period, the number completing both periods, or the number included in any analysis. Enrollment should not be taken as evidence that every participant completed every assessment.
Each product was worn bilaterally on an extended-wear, overnight basis for 7 days. The record says the deposit assessment occurred after 2-5 hours of open-eye lens wear, using a slit-lamp. It does not describe the interval between product periods, any washout procedure, adherence to wear instructions, or the precise timing of assessments within the stated assessment window.
The listed sponsor is Alcon Research. The record gives a start date of 2008-03, a primary completion date of 2008-10, and a completed status. It does not report a statistical analysis plan, sample-size justification, or details about how the sequence assignment was generated or concealed. Those design features are not reported in the registry record.
4. Participant Flow and Accounting
The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.
Before assignment: Participants meeting eligibility criteria at the screening visit were enrolled into the study. 48 hours of no lens wear prior to Visit 1 served as the washout period. This reporting group includes all enrolled and dispensed participants.
First Intervention, 7 Days (+0/-1)
| Stage | Balafilcon A / Etafilcon A | Etafilcon A / Balafilcon A |
|---|---|---|
| STARTED | 27 | 27 |
| COMPLETED | 27 | 27 |
| NOT COMPLETED | 0 | 0 |
Second Intervention, 7 Days (+0/-1)
| Stage | Balafilcon A / Etafilcon A | Etafilcon A / Balafilcon A |
|---|---|---|
| STARTED | 27 | 27 |
| COMPLETED | 27 | 27 |
| NOT COMPLETED | 0 | 0 |
Analysis population for the primary outcome, as defined in the registry: All enrolled participants.
5. Baseline Characteristics
The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.
| Characteristic | Unit | Overall |
|---|---|---|
| Participants analysed | 54 | |
| Age Continuous | years | 32.35 (SD 12.71) |
| Sex: Female, Male: Female | Participants | 42 |
| Sex: Female, Male: Male | Participants | 12 |
6. Primary Endpoint
The registry lists the primary outcome as Front Surface Lens Deposits, measured over 7 days.
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | not applicable |
| Unit | Participants |
| Endpoint classification | Binary Endpoint |
The primary outcome is titled Front Surface Lens Deposits and is measured in participants. It describes film and discrete deposits assessed with a slit-lamp after 2-5 hours of open-eye lens wear, following the stated 7-day wear period. The record defines film deposits on a 5-point scale: grade 0 is a clean surface; grade 1 is slight deposition occupying 1-5% of the lens front surface; grade 2 is mild deposition occupying 6-15%; grade 3 is moderate deposition occupying 16-25%; and grade 4 is severe deposition occupying >25%.
Discrete deposits also use a 5-point scale. The grades range from a clean surface at grade 0, through microdeposits and macro deposits, to one or more jelly bumps at grade 4. The registry defines a participant classification of Front Surface Lens Deposits <2 when both film and discrete deposits are below grade 2, and a classification of front surface lens deposits >1 when either measure, or both, is above grade 1.
These classifications provide a structured way to describe visible deposits rather than relying only on an unstructured impression. The outcome can distinguish deposit type and severity, but the registry record does not report the observed participant counts in any category. It therefore does not establish how the classifications were distributed by product.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The record gives substantial detail about how front-surface deposits were assessed, but it does not provide the outcome values needed to describe what the study observed. No participant counts for the deposit classifications are reported, and no product comparison is listed. The relative findings for balafilcon A and etafilcon A are therefore not reported in the registry record.
The registry lists one primary outcome measure but indicates that the result was not reduced to a single comparison because it has several categories or time points. It also lists zero analyses. These entries should be read as an absence of posted inferential results, not as evidence that the products had identical results or that an analysis found no difference. No effect estimate, confidence interval, or p-value for the deposit outcome is reported in the registry record.
General statistical interpretation depends on both the estimated effect and its uncertainty. A confidence interval describes a range of values compatible with the data and the analysis assumptions; it helps readers judge precision. A p-value, when reported, addresses compatibility with a specified null model and is not a measure of clinical importance. Neither type of statistic can be interpreted for this endpoint without a reported estimate and analysis.
The crossover structure matters when interpreting any future or separately reported comparison. Measurements from the same participant may be related, and an analysis that respects this pairing can differ from one that treats observations as independent. The registry record does not say how the sequence, period, or within-participant structure was handled analytically. It also does not report whether there were period effects, carryover concerns, or adjustments for them. No conclusion about these features can be drawn from the posted results.
The assessment describes both film and discrete deposits and defines two threshold classifications. Those details establish what the endpoint means, but they do not reveal the frequency or severity of deposits after either product. The evidence available in the registry record supports a description of the intended measurement and study design, not a conclusion about the direction, magnitude, or precision of a product difference.
9. Statistical Methods Explained
The registry describes a randomized, single-masked crossover study. Randomization means that assignment to the sequence of product use was intended to be determined by a chance-based process. A crossover design assigns interventions in sequence, so participants may contribute observations under each product. This can be useful when the outcome is measured in the same person under different conditions, because stable differences between participants may be less influential in a within-participant comparison.
The registry record identifies the two sequences but does not describe the randomization method, allocation concealment, the identity of the masked party, or how treatment order was represented in an analysis. It also does not state whether a washout period was used. The design label alone does not resolve these practical or analytic details.
What does a crossover comparison require?
General statistical explanation: observations collected from the same participant are often correlated. A suitable crossover analysis accounts for that relationship rather than treating every product-period observation as independent. Period and sequence can also matter: outcomes may vary over time, and the order in which products are used may influence interpretation. The registry record does not report whether these features were evaluated or included in the analysis.
The study describes each product as worn bilaterally for 7 days and deposit assessment after 2-5 hours of open-eye lens wear. Those timings define the setting for the measurement, but do not by themselves specify the statistical unit used in an analysis. The outcome is expressed in participants, while the assessment is made on lenses. The registry record does not provide further detail on how lens-level observations, if any, were combined for each participant.
How should the deposit scales be understood?
The endpoint uses ordinal grades. Ordinal categories have a defined order, from no deposition through increasing descriptions of deposits, but the distance between adjacent grades is not necessarily equal. For example, a change between neighboring categories need not represent the same amount of physical change at every point on the scale. Treating such scores as categories, rather than assuming equal numeric spacing, is one possible analytic approach; the registry record does not report the approach used.
Film and discrete deposits capture different described features. The film scale refers to the proportion of the lens front surface occupied, while the discrete scale describes deposit forms such as microdeposits, macro deposits, or jelly bumps. The registry then defines participant classifications using thresholds on these measures. A threshold can make a result easier to communicate, but it also reduces detail compared with retaining the full grades. The posted record does not give the counts needed to see how much information was lost through categorization.
What does the absence of an analysis mean?
The registry lists zero analyses and explains that the primary outcome has several categories or time points and was not reduced to one comparison. This means no single inferential result for the outcome is presented in the record. It does not establish that the study collected no measurements; rather, the registry does not report an analysis that can be interpreted as a comparison between the lens products.
General statistical explanation: an effect estimate describes the direction and size of a contrast, while its confidence interval describes the uncertainty around that estimate under the model used. A p-value is meaningful only in relation to a defined analysis and hypothesis. Without a reported comparison, there is no basis for describing statistical significance or precision for the primary outcome. A missing p-value should not be treated as a p-value that failed a threshold.
Why can over-dispersion matter?
General statistical explanation: for count outcomes, some statistical models make assumptions about how variable the counts are relative to their average. Over-dispersion means that variability is greater than such a model expects. If not accounted for, standard errors can be too small and uncertainty can appear understated. This trial’s primary outcome is described as participant classifications, not as a reported count model, and the registry record does not identify an over-dispersion assessment or model. This concept is therefore general rather than a description of an analysis performed in this study.
The record gives planning assumptions for sample-size illustrations based on an observed effect, with a two-sided significance level of 0.05, equal allocation between arms, and a normal approximation; the stated effect to detect is a fraction of the observed effect. Such planning illustrations are not observed trial outcomes and are not evidence of the trial’s achieved power. The registry does not report its own sample-size justification, and the posted record contains no outcome comparison from which the observed effect can be interpreted.
10. Multiplicity, Missing Data and Analysis Populations
The registry lists one primary outcome measure, but its description includes film and discrete deposit assessments and two participant classifications: Front Surface Lens Deposits <2 and front surface lens deposits >1. It also states that the outcome has several categories or time points and was not reduced to one comparison. These features create multiple ways to describe the endpoint, but the record does not explain which result was intended to be primary for inference or how any multiplicity was handled.
Multiplicity arises when several outcomes, thresholds, time points, or comparisons are assessed. General statistical explanation: examining multiple results can increase the chance that at least one appears notable by chance. Prespecified priorities and appropriate adjustments can help make interpretation clearer. The registry record does not report a multiplicity procedure or identify a hierarchy among the classifications, so no claim about such control can be made.
The record does not report missing-data counts, reasons for missing assessments, imputation methods, or sensitivity analyses. It names all enrolled participants as the primary outcome population, but does not define the analysis population beyond that description. It also does not report how incomplete crossover participation, if any, was handled. These missing details limit assessment of whether the posted outcome would represent all enrolled participants or only those with available measurements.
Although enrollment is reported as 54, that figure does not establish how many participants contributed data to each product-period assessment. The registry record does not report a flow of participants through the study or the denominator used for each deposit classification. No assumptions about missingness or analysis populations should be inferred.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Balafilcon A Contact Lenses | 0 | 54 | 0.0% |
| Etafilcon A | 0 | 54 | 0.0% |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 5% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Balafilcon A Contact Lenses | 0 of 54 |
| Etafilcon A | 0 of 54 |
The adverse-event record lists Balafilcon A Contact Lenses and Etafilcon A as groups. For each group, serious adverse events are recorded as 0 among 54 at risk, and other adverse events are also recorded as 0 among 54 at risk. These are the posted counts and denominators; they should be read as registry entries, not converted into percentages or treated as proof that events could not occur.
The death fields are null, so death counts are not reported in the registry record. No serious adverse-event terms are listed. The record also does not provide a narrative about event collection, attribution, duration of follow-up for safety, or whether the counts refer to particular periods of the crossover. The denominators shown for the product groups do not establish how repeated exposure or within-participant observation was handled.
Zero recorded events in these entries indicates that the registry lists no events in the displayed categories for the stated risk groups. It does not show the precision of a risk estimate, nor does it establish absence of risk. The serious-event and other-event counts should not be used to infer unreported safety outcomes or to compare products statistically.
12. What the Result Does, and Does Not, Mean
This record is informative about the design and the planned measurement. It identifies a randomized, single-masked crossover structure, the order in which each product could be worn, the 7-day extended-wear periods, and the slit-lamp assessment after 2-5 hours of open-eye wear. It also defines film and discrete deposit grades and the participant thresholds used to classify deposits.
However, the registry record does not report the resulting deposit counts or an analysis comparing balafilcon A with etafilcon A. There is no reported effect estimate, confidence interval, or p-value for the primary outcome. Accordingly, the record does not establish which product had more deposits, whether the products differed, or how precise a difference might be. A lack of posted comparison is not evidence of equivalence or of no difference.
The posted safety counts list no serious or other adverse events in the recorded groups, while death counts are not reported. Those entries describe what is recorded in the registry; they do not quantify uncertainty or support a broader claim about safety.
General statistical explanation: a result is most informative when readers can assess the estimated contrast, its uncertainty, the analysis population, and the assumptions behind the analysis. For a crossover trial, that includes consideration of paired observations, period, and sequence. Those pieces are not reported for the deposit outcome, so the registry entry supports a design-level description rather than an efficacy conclusion.
The findings should therefore be understood within the limits of the posted record: the measurement method is described, but the primary outcome results are not. No treatment recommendation or clinical decision follows from the record alone.
13. Why This Trial Matters Statistically
The statistical interest of this study lies in the combination of a crossover design and a graded, multidimensional endpoint. Crossover designs can make within-participant comparisons possible, but require analysis that respects the relationship between observations from the same participant and considers the sequence and period structure. The registry gives the sequence descriptions, while leaving the analysis details unreported.
The endpoint also illustrates how a clinical measure can move from observed features to categories. Film and discrete deposits are assessed separately using ordered grades, then summarized with threshold classifications. Such thresholds can simplify communication, while potentially obscuring distinctions among grades and deposit types. Without reported category counts, readers cannot examine that tradeoff empirically for this study.
Another statistical issue is the difference between a detailed outcome definition and an interpretable result. The registry specifies the assessment procedure and thresholds but lists zero analyses and says the outcome was not reduced to a single comparison. As a result, neither an effect estimate nor its precision is available for interpretation. This distinction is important: a well-described measurement does not by itself show what the data found.
The record also highlights why reporting the analysis population, missing assessments, and handling of crossover features matters. Those details are needed to understand who contributed to each product-period result and how the comparison was estimated. They are not reported in the registry record, limiting independent statistical interpretation.
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 main limitation for interpreting the primary outcome is that the registry record does not report participant counts by deposit category or an analysis comparing the products. The outcome includes multiple scales and classifications, and the record says it was not reduced to one comparison. Consequently, the direction, magnitude, and precision of any product contrast cannot be assessed.
Details needed to evaluate the crossover analysis are also absent. The record does not report the statistical model, treatment of within-participant correlation, assessment of period or sequence effects, or handling of possible carryover. It does not describe washout procedures. These omissions do not establish that the design or analysis was inadequate; they mean those features cannot be evaluated from the registry entry.
The record does not report participant flow, completion of both lens periods, missing outcome data, reasons for missingness, or the methods used to handle incomplete assessments. Although all enrolled participants are named as the primary outcome population, the record does not provide the contributing denominator for each assessment. Thus enrollment cannot be equated with completed outcome observation.
The endpoint definition provides ordinal grades and threshold categories, but no information about assessor training, reproducibility, or blinding of the assessor. Single masking is listed, but the masked party is not identified. The registry also does not report the protocol-level rationale for the endpoint or sample size. These limitations constrain interpretation of measurement reliability, analysis choices, and design planning.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Evaluation of Deposits on Contact Lenses Worn Extended Wear — NCT00725530.
- Registry record last updated 2012-08-22; status last verified 2012-07.
- Results first posted 2012-08-22.
- 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.
Continue through the Clinical Biostats statistical pathway
Use this trial's endpoint as a starting point for deeper study of effect measures, confidence intervals, and sample-size planning.
18. Record Summary
The registry record describes a completed randomized, single-masked crossover study of balafilcon A and etafilcon A contact lenses in participants with myopia. Enrollment was 54. Each product was worn bilaterally overnight for 7 days, with front-surface deposits assessed by slit-lamp after 2-5 hours of open-eye lens wear.
The primary measure defines film and discrete deposit grades and participant classifications based on thresholds. The record lists zero analyses and does not report the outcome counts or a product comparison. The statistical findings for deposits are therefore not reported in the registry record. Safety entries list 0 serious and 0 other adverse events among 54 at risk in each product group; death counts are not reported.