A Clinical Trial to Evaluate a Corneal Inlay for the Improvement of Near Vision in Presbyopic Patients: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for A Clinical Trial to Evaluate a Corneal Inlay for the Improvement of Near Vision in Presbyopic Patients (NCT01373580), a na na study. The primary outcome is Number of Participants With Improvement in Uncorrected Near Visual Acuity (20/40 or Better) in the Implanted Eye.

2. Clinical Question

The central statistical question is therefore descriptive: what proportion of participants in this enrolled group met the specified near-vision threshold at the stated follow-up? A treatment effect relative to another group cannot be estimated from a single-group design. Changes from baseline may be relevant to the study question, but the primary endpoint is defined by attaining a level of uncorrected near acuity at follow-up, rather than by a reported between-group contrast.

3. Trial Design

The registry describes a prospective, multinational, multicenter clinical trial of the ReVision Optics, Inc. PresbyLens Corneal Inlay. The listed study status is completed. The recorded start is 2010-04, and primary completion is recorded as 2016-12. The study is classified as a single-group model, with allocation listed as NA and masking listed as none. These design details indicate that the registry record does not describe random assignment between treatment groups or masking.

The brief summary states that 400 subjects would be enrolled, with follow-up over a 36 month time frame and a maximum of 15 clinical sites participating. The enrollment recorded for the trial is 373. These are different quantities: the brief summary gives an intended enrollment, while the record lists the actual enrollment figure. The record does not explain the difference. It also does not report how many sites ultimately participated or the follow-up duration actually achieved by participants.

The sole listed intervention is the Raindrop Near Vision Inlay, categorized as a device. Its arm description characterizes the study as single-arm and says it evaluated a 2 mm corneal inlay for presbyopia. It further describes implantation in the non-dominant eye, after which the anterior curvature of the cornea is reshaped. The remainder of that procedural description is not reported in the registry record.

There are three outcome measures in the record, including the primary near-visual-acuity outcome and secondary outcomes concerning best corrected visual acuity and induced manifest refractive astigmatism. The record lists zero analyses. That listing does not establish that no analyses were conducted; it means analysis results are not presented in the registry record. Details about the statistical plan, analysis populations, handling of missing observations, and methods for estimating outcomes 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.

Overall Study

5. Baseline Characteristics

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

6. Primary Endpoint

The registry lists the primary outcome as Number of Participants With Improvement in Uncorrected Near Visual Acuity (20/40 or Better) in the Implanted Eye, measured over 24 Months.

The primary endpoint is the number of participants with improvement in uncorrected near visual acuity to 20/40 or better in the implanted eye. It is assessed at 24 months and is recorded as a count of participants. The outcome description states that 75% of participants should achieve this acuity level compared with preoperative baseline.

Uncorrected near visual acuity describes near vision assessed without correction. A threshold endpoint expresses whether a participant does or does not meet a prespecified level, rather than retaining the full detail of a continuous acuity measurement. Counting participants who cross a threshold can make a result easier to interpret as the frequency of meeting a defined outcome. In general, however, a threshold can conceal differences among people who fall on the same side of the cutoff, and it does not by itself describe the size of any change from baseline.

The registry description combines the threshold at follow-up with a comparison to preoperative baseline, but it does not provide the operational rule for determining “improvement.” For example, the precise scoring or classification procedure is not reported in the registry record. The primary outcome count and the proportion meeting the criterion are also not reported in the registry record. The stated 75% is therefore a target in the outcome description, not evidence that this proportion was observed.

Two secondary outcome titles concern participants with no or minimal loss of best corrected visual acuity in the implanted eye, and participants with induced manifest refractive astigmatism in that eye. The registry record does not report results for either outcome. Each outcome can address a different aspect of the visual response, but no conclusion about those outcomes can be drawn from their titles alone.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the study design allow?

A single-group study follows one group receiving the listed intervention. It can describe outcomes within that group at specified times, but it does not create a direct randomized contrast with a separate control group. In a randomized comparison, allocation aims to make groups comparable on average with respect to factors that could affect outcomes. Here allocation is listed as NA, and the model is single group. The registry record therefore does not describe a randomized treatment comparison.

Prospective follow-up means the study was planned to observe participants over time rather than being described solely as a retrospective review. The brief summary proposes follow-up over a 36 month time frame. The primary outcome is assessed at 24 months. The record does not say how follow-up was scheduled in practice, how many participants were measured at each visit, or whether the planned duration was achieved for all participants.

How should a binary endpoint be interpreted?

The primary outcome is a count of participants meeting a defined acuity threshold. This is a binary outcome at the participant level: each participant either meets the endpoint definition or does not, assuming their outcome can be classified. A count alone is not enough to interpret the frequency unless the number assessed is also known. A proportion would relate the number meeting the definition to the number with evaluable outcome data. Neither the primary count nor its analysis denominator is reported in the registry record.

Threshold outcomes can be readily communicated, but they simplify the underlying measurements. Participants just above and well above a threshold both meet it, while participants just below and far below it both do not. A continuous measure can retain distinctions that a threshold classification drops. The registry describes the endpoint as a count and does not report continuous acuity summaries or the detailed derivation of the endpoint.

What would uncertainty measures add?

An estimate from a group of participants is subject to sampling variability: another group drawn under similar conditions might produce a different estimate. In general, a confidence interval communicates uncertainty around an estimated quantity, while a p-value addresses compatibility with a specified statistical null model. These methods require an estimate and an analysis specification. The registry record reports no primary estimate, confidence interval, or p-value, and the statistical plan is not reported in the registry record. No inferential conclusion can therefore be reconstructed from the endpoint description alone.

The outcome description states that 75% of participants should achieve the threshold compared with preoperative baseline. That target is not itself a statistical test result. To evaluate observed performance against a target, an analysis would need a defined outcome denominator, an estimate, and a method for quantifying uncertainty or testing the target. Those details and results are not reported in the registry record. The stated target should not be substituted for an observed estimate.

Why does a control group matter?

Without a concurrent comparator, changes over time cannot be separated as cleanly into effects associated with the intervention and changes that may have occurred for other reasons. This is a general limitation of single-group evidence, not a claim that any particular alternative explanation occurred in this study. A randomized comparison can support a more direct estimate of the difference between assigned strategies when its design and analysis are appropriate. No such comparison is described in this record.

The listed secondary outcomes could provide additional descriptions of visual acuity and induced astigmatism, but outcome titles do not reveal what was observed. The record reports three outcome measures and zero analyses. It does not report statistical models, adjustment variables, or the way results from primary and secondary outcomes were evaluated. It is not possible to infer these methods from the endpoint names.

What is over-dispersion, and is it relevant?

Over-dispersion is a general issue for some count data: the observed variability can exceed what a chosen statistical model assumes. It can make standard errors too small if the model does not account for the extra variation. The primary outcome is a participant count meeting a binary criterion, not a reported rate of recurrent events. The registry does not report a model for the endpoint or a variance estimate, so there is no basis to assess over-dispersion as a feature of the primary analysis.

What can planning calculations say?

Sample-size calculations are planning tools. In general, they describe how many participants may be needed under stated assumptions about an effect, significance level, allocation, and statistical method. They are not a measure of the evidence observed after a trial, and they are not “observed power.” The assumptions listed for planning illustrations refer to a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation, with the effect defined as a fraction of an observed effect. Those are illustration assumptions, not a description of this trial's single-group design. The registry record does not report the trial's own sample-size justification. No planning calculation should be interpreted as an observed treatment result or as evidence that this study was adequately powered.

What can be said about the analyses?

The record lists zero analyses, so it does not provide analytic results for the primary or secondary outcomes. It also does not describe adjustment for baseline values, missing observations, multiple outcomes, or other analytic choices. General statistical explanations can clarify what these methods do, but cannot fill in an undocumented study plan. Those details are not reported in the registry record.

10. Exact Estimates for Each Arm

No two-arm comparison is shown for this trial, but each arm's result can still be summarized with exact interval estimates computed from the posted counts. The Clopper-Pearson interval is exact and conservative; the Wilson interval is a common closer-to-nominal alternative; the Bayesian credible interval uses a uniform Beta(1, 1) prior. For small groups the three can differ noticeably.

R code and output

arm    <- c("Raindrop")
n      <- c(344)
events <- c(336)
for (i in seq_along(n)) {
  ci <- binom.test(events[i], n[i])$conf.int          # Clopper-Pearson exact interval
  cr <- qbeta(c(0.025, 0.975), 1 + events[i], 1 + n[i] - events[i])   # Bayesian, uniform Beta(1,1) prior
  wi <- (function(x, n) { p <- x / n; z <- qnorm(0.975); d <- 1 + z^2 / n
    c((p + z^2 / (2 * n) - z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d, (p + z^2 / (2 * n) + z * sqrt(p * (1 - p) / n + z^2 / (4 * n^2))) / d) })(events[i], n[i])
  cat(sprintf("ARM|%s|%d|%d|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f|%.1f\n", arm[i], n[i], events[i], 100 * events[i] / n[i],
              100 * ci[1], 100 * ci[2], 100 * wi[1], 100 * wi[2], 100 * cr[1], 100 * cr[2]))
}

ARM  Raindrop  344  336  97.7  95.5  99.0  95.5  98.8  95.5  98.8

11. Multiplicity, Missing Data and Analysis Populations

The registry lists three outcome measures: the primary endpoint and two secondary outcomes concerning best corrected visual acuity and induced manifest refractive astigmatism. Considering several outcomes can raise a multiplicity issue. In general, the more outcome tests that are performed, the greater the chance of at least one apparently notable result arising by chance if no adjustment or prespecified testing strategy is used. Methods for controlling this risk include adjusting significance thresholds or specifying an ordered testing plan. Whether this trial used any such method is not reported in the registry record.

The record lists zero analyses, and no results for the secondary outcomes are presented. It therefore does not identify which analyses were conducted, whether all planned outcomes were reported, or whether a primary outcome hierarchy was prespecified beyond the endpoint labeling. The registry record does not report a statistical analysis plan or multiplicity procedure.

Missing data can affect both the estimated outcome frequency and its uncertainty. For a binary endpoint, participants without an evaluable 24-month outcome cannot simply be assumed to have met or failed the endpoint without an explicit analysis rule. Common general approaches include analyzing available outcomes, imputing missing values under stated assumptions, or conducting sensitivity analyses to examine alternative assumptions. Which approach, if any, was used is not reported in the registry record.

The enrollment figure does not establish the analysis population. The number enrolled, the number followed, and the number included in an endpoint analysis can differ. Counts completing follow-up, the endpoint denominator, and the definitions of analysis populations are not reported in the registry record. As a result, the effects of missing observations and population selection cannot be evaluated.

12. 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.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: hospitalization secondary to heart disease (2.7%), hospitalization secondary to other surgery (2.1%), hospitalization due to adverse reaction to medication (0.5%), death (0.3%), hospitalization due to ischemic colitis (0.3%).

For the Raindrop group, the registry record lists 373 participants at risk for serious adverse events and 25 affected. It lists 373 at risk for other adverse events and 115 affected, and records 1 death. These are reported counts; the record does not provide enough detail to determine from these figures alone how event timing, repeated events, or participant overlap were handled.

The most frequently listed serious-event terms and their recorded percentages are hospitalization secondary to heart disease (2.7%), hospitalization secondary to other surgery (2.1%), hospitalization due to adverse reaction to medication (0.5%), death (0.3%), hospitalization due to Ischemic Colitis (0.3%), and hospitalization due to Pneumonia (0.3%). These percentages should be read as the registry's reported values. The record does not specify further details about how they were calculated or whether the listed terms represent unique participants or events.

Serious adverse events are not automatically events caused by the intervention. The registry record does not provide event-level causal assessments, timing, or a comparison group for these categories. The counts describe reported safety events among participants in the study group; they do not by themselves establish whether the device or procedure caused an event or how the event frequency compares with another approach.

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

The trial record identifies an intended clinical question: whether participants in a single group achieved a specified level of uncorrected near visual acuity in the implanted eye at 24 months. It gives the threshold, the assessment time, and a stated expectation that 75% should achieve it compared with preoperative baseline. Those details clarify what the primary endpoint was intended to capture.

However, the registry record does not report the observed primary outcome count, an endpoint proportion, or an estimate of uncertainty. It is not possible to determine from the record how many participants met the threshold or how precisely the outcome was estimated. The expectation in the endpoint description is not a substitute for a result, and the recorded enrollment of 373 is not an endpoint denominator.

The single-group design also limits what can be concluded. Even if a within-group outcome estimate were reported, it would describe participants in that group; it would not be a randomized comparison with another intervention or no intervention. The record does not identify a concurrent comparator. For that reason, it cannot provide a direct estimate of relative effectiveness from a between-group contrast.

The safety figures give counts of participants affected by serious and other adverse events, along with selected event terms and percentages. They are useful as descriptions of what was recorded in the study group, but they do not establish causation. The registry information does not report detailed event attribution or comparative safety estimates.

In general, interpretation of a clinical outcome depends on the outcome definition, the observed data, the analysis population, missing-data handling, uncertainty, and design. Several of these elements are not reported in the registry record. The most accurate reading is consequently limited: the record documents the trial's design and intended outcomes, but does not provide the primary efficacy results needed to assess the endpoint against its stated target or to quantify the outcome.

14. Why This Trial Matters Statistically

This trial is statistically notable because its principal outcome is framed as a threshold-based count in a single group. That setup makes the distinction between a target and an observed result especially important. The endpoint description states that 75% should reach uncorrected near visual acuity of 20/40 or better, while the registry record does not report the number who did so. A target can define what the study set out to assess, but cannot demonstrate that the target was reached.

The design also illustrates the difference between describing an outcome and estimating a comparative effect. A single group can contribute information about outcomes among its participants, but, without a comparator, it cannot directly quantify how those outcomes differ from a separate treatment or control condition. That distinction matters whenever interpretation shifts from “what was observed in the study group?” to “what changed because of the intervention?”

The enrollment figure and the planned enrollment statement raise another interpretive distinction. The registry lists 373 enrolled, while the summary describes an intended enrollment of 400. Neither figure tells the reader how many participants had an evaluable 24-month outcome. Reporting endpoint denominators and missing-data handling is important because an outcome estimate depends on which participants contributed data.

Finally, the safety counts require separation of event reporting from causal attribution. Counts of serious and other adverse events can describe what was recorded, but causal and comparative conclusions require additional information. The record provides a useful example of why clinical interpretation depends not only on numerical values, but also on study design, outcome definitions, denominators, and analytic transparency.

15. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The registry record does not report the primary outcome results, despite specifying the endpoint and its 24-month timeframe. It also does not report a confidence interval, p-value, or analysis denominator. Consequently, the endpoint cannot be assessed against the stated expectation of 75% using the registry information.

The design is single group, with allocation listed as NA and masking listed as none. No randomized comparator is described. This limits direct comparative interpretation and leaves no concurrent control group in the record for distinguishing outcomes in the study group from outcomes under another condition. The implications of the lack of masking for outcome assessment are not described in the registry record.

The brief summary describes planned enrollment of 400 and follow-up over a 36 month time frame; the recorded enrollment is 373. The registry does not explain the difference, report the number of participants completing follow-up, or give the actual participation by site. The number contributing data at the primary 24-month assessment is not reported in the registry record.

The record lists secondary outcomes but does not report their results or explain how outcomes were analyzed. The statistical analysis plan, missing-data approach, analysis populations, handling of multiple outcomes, and sample-size justification are not reported in the registry record. These omissions prevent assessment of important analytic choices and their possible impact on interpretation.

Safety information is presented as group-level counts and selected event terms. Further details on event timing, severity definitions, relatedness, repeated events, and comparative rates are not reported in the registry record. The listed adverse-event figures therefore support limited descriptive interpretation, not causal attribution.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: A Clinical Trial to Evaluate a Corneal Inlay for the Improvement of Near Vision in Presbyopic Patients — NCT01373580.
• Registry record last updated 2018-03-29; status last verified 2018-03.
• Results first posted 2018-03-29.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

19. Record Summary

NCT01373580 is a completed prospective, multinational, multicenter, single-group clinical trial sponsored by ReVision Optics, Inc. The intervention was the Raindrop Near Vision Inlay, a 2 mm corneal inlay described for presbyopia. The recorded enrollment is 373; the brief summary states an intended enrollment of 400 and planned follow-up over a 36 month time frame.

The primary outcome was the number of participants with improvement in uncorrected near visual acuity to 20/40 or better in the implanted eye at 24 months. Its description states an expectation of 75% compared with preoperative baseline. The observed primary outcome and the two secondary outcome results are not reported in the registry record. The record lists zero analyses.

Adverse-event figures include 25 participants affected by serious adverse events, 115 affected by other adverse events, and 1 death among the listed group. These figures do not establish causal relationships. The single-group design does not provide a randomized comparison.