Virtual Reality Mobility Training System for Veterans With Vision Loss: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Virtual Reality Mobility Training System for Veterans With Vision Loss (NCT00333879), a na na study. The primary outcome is Accuracy in Judging Direction of Traffic at Traffic Intersection.

2. Clinical Question

The study addresses whether a simulated auditory environment could convey spatial information relevant to orientation and mobility training. It is a feasibility and proof-of-concept question, not a comparison of the device with another training method. The registry record describes the primary task as judging traffic direction at an intersection. Participants were asked to classify traffic as moving on the street in front of them or on the street beside them.

The record also lists accuracy in selecting an appropriate time to cross the street as a secondary outcome. However, it does not report a numerical result for that outcome. The primary-outcome description says that the study ended after none of the subjects could identify the location of traffic vehicles when using the intervention across multiple (4) trials. That narrative provides context for the stopping decision, but it is not a complete participant-level account of accuracy or a reported estimate of the primary endpoint.

3. Trial Design

This was a completed, single-group proof-of-concept study sponsored by the US Department of Veterans Affairs. The registry lists enrollment of 4 and identifies blindness as the condition. The intervention was a device named the Virtual Sound System, described as a way to simulate street-crossing conditions. No separate control arm is described, so the study does not make a like-for-like comparison between the device and another intervention.

The record lists allocation as NA and masking as NONE. The phase is listed as NA. These entries do not establish a randomized allocation process or blinded outcome assessment. The study title and summary focus on veterans with vision loss and the use of a virtual reality holographic sound system as an audiological orientation and mobility training tool. The summary calls it a two-year proof-of-concept study. The registry dates for study start and primary completion are both 2009-03; the record does not explain the relationship between those dates and the two-year description.

For the primary task, assessment was scheduled as 4 trials over 30 minutes after 30 minutes of training. Each trial lasted 5 minutes, with a 2 minute and 30 second break between trials. During each trial, traffic stopped and started 5 times, moving in one of two randomly selected directions: left and right in front of the participant, or forward and back along the street beside the participant. The participant had to distinguish the two locations using the sound information.

The registry says that the initial pilot design called for 16 subjects to provide data of significance based on a power analysis. It also says the study terminated at 4 subjects when none of the subjects could identify the location of traffic vehicles using the intervention across multiple (4) trials. Details of the original power analysis, including its assumptions and target effect, are not reported in the registry record. The registry does not describe a comparison group, a prespecified stopping boundary, or an interim-analysis procedure.

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: All 4 subjects were accepted for the study. None were excluded.

Overall Study

Analysis population for the primary outcome, as defined in the registry: Initial pilot study design called for 16 subjects to provide data of significance based on a power analysis. Study terminated at 4 subjects when none of the subjects could identify the location of traffic vehicles when using the intervention across multiple (4) trials.

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 Accuracy in Judging Direction of Traffic at Traffic Intersection, measured over 4 trials over 30 minutes after 30 minutes of training.

The primary endpoint is titled Accuracy in Judging Direction of Traffic at Traffic Intersection. Its unit is participants and its recorded parameter is a number, rather than a continuous measurement such as a distance or time. In practical terms, the task asked whether the participant could identify traffic moving across the street in front of them rather than traffic moving along the street beside them. The participant could give only those two location responses.

The task was intended to assess whether the device conveyed directional sound information in a simulated intersection. The registry specifies a performance threshold: the participant had to identify direction correctly at least 4 out of five times for the equipment to be counted as efficacious for presenting accurate 3D sound information. This threshold describes the study's stated criterion; it is not itself a reported result.

The primary assessment was scheduled after training and included 4 trials over 30 minutes. Traffic direction changed repeatedly within a trial, providing repeated opportunities to make the required distinction. The record does not provide individual responses, a participant-level accuracy distribution, or a numerical endpoint estimate. It therefore does not establish from a reported endpoint count how many participants met the criterion. The narrative about termination reports that none of the subjects could identify vehicle location across multiple (4) trials, but it does not replace a complete numerical outcome report.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The study is classified as single-group. In general, a single-group design describes observations made under an intervention without a concurrent control group. It can be useful for early feasibility work, but it does not provide the direct comparison needed to separate intervention effects from other explanations. Here, allocation is listed as NA, masking as NONE, and no like-for-like control comparison is described in the registry record.

What does the primary measure count?

The primary outcome is named Accuracy in Judging Direction of Traffic at Traffic Intersection. Its recorded unit is participants, and its parameter is a number. The task itself asks for a categorical response: traffic is either moving on the street in front of the participant or on the street beside the participant. The study description sets an accuracy criterion of at least 4 out of five correct responses. These details define the intended assessment, but the record does not provide the participant-level response data or a numerical count of those meeting the criterion.

The registry also characterizes the outcome type as binary and describes that type as participants with an event, counted as counts. That characterization should not be mistaken for a reported analysis. There are no analyses listed, and no model or test result is reported. With only a task definition and a stopping narrative, it is not possible to reconstruct an inferential analysis or determine the precision of a participant-level rate.

What would an estimate and interval add?

As a general statistical concept, an estimate gives a numerical summary of the observed outcome, while a confidence interval describes uncertainty around that estimate under a specified analysis. The interval's interpretation depends on the outcome definition, the sampling assumptions, and the analysis method. None of those numerical inferential results is reported for this primary outcome in the registry record. Without them, readers should not infer a degree of precision from the study's stated threshold or from its enrollment alone.

Repeated responses within a participant can also matter statistically. Responses from the same person may be related rather than independent observations. A method that treats all responses as independent can understate uncertainty when within-person responses are correlated. General approaches for repeated binary responses can account for this dependence, but the registry does not report whether any such method was planned or used. The description of several trials does not reveal how repeated observations were handled in analysis.

What can be learned from the design?

Because the model is single-group, there is no randomized comparison on which to base a treatment-effect contrast. A descriptive summary could report task performance under the study conditions, but an effect relative to another training approach cannot be estimated from this design alone. The record also does not describe blinded assessment. In general, knowledge of the intervention or task can influence responses or their assessment; whether that occurred in this study is not reported.

The primary assessment followed 30 minutes of training and involved 4 trials over 30 minutes. Each trial lasted 5 minutes, with a 2 minute and 30 second break between trials. Traffic stopped and started 5 times during each trial, with direction randomly selected from the two described movement patterns. These details explain the structure of the task, but they do not establish that the sound system's performance was assessed against an independent reference standard. The record does not report such a standard or a separate validation procedure.

How should planning illustrations be read?

The registry says the pilot was initially designed for 16 subjects, based on a power analysis intended to provide data of significance. The calculation's target effect, variance assumptions, and other details are not reported in the registry record. A planned enrollment is not an outcome and does not describe the precision actually achieved.

The planning assumptions stated for illustrations based on the observed effect include a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. The effect to detect is described as a stated fraction of the observed effect. In general, such illustrations explore how a hypothetical future study might be sized under chosen assumptions. They are not observed power and do not provide evidence that an intervention effect exists. The equal-allocation, two-arm assumption also differs from this study's single-group model, so those planning illustrations should not be interpreted as a design description for this pilot. No specific original power-analysis method is reported in the registry record.

Over-dispersion is a general concern when observed variation exceeds what a simple statistical model expects. It can arise in count data when observations vary more than a basic model allows, and methods that ignore it can produce uncertainty estimates that are too narrow. The primary outcome is described in terms of participant counts, but the registry supplies no dispersion estimate and reports no fitted model. It is therefore not possible to assess over-dispersion or to identify a suitable count-model correction from the 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("Virtual Sound System")
n      <- c(4)
events <- c(0)
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  Virtual Sound System  4  0  0.0  0.0  60.2  0.0  49.0  0.5  52.2

11. Multiplicity, Missing Data and Analysis Populations

The registry lists 2 outcome measures. The primary outcome concerns accuracy in judging traffic direction, and the secondary outcome concerns accuracy in selecting an appropriate time to cross the street. The record does not provide a numerical result for the secondary outcome or a complete numerical result for the primary outcome.

When a study assesses multiple outcomes, general statistical practice considers whether the analysis plan accounts for the possibility of chance findings across several tests. The registry record does not report a multiplicity adjustment, a hierarchy for interpreting outcomes, or a prespecified testing strategy. Since it lists no analyses, there are no reported p-values or inferential comparisons whose multiplicity adjustment can be evaluated.

Missing-data handling is not reported in the registry record. The record does not specify whether any observations were incomplete, how incomplete assessments would be handled, or whether participants with incomplete data were included in an analysis. An analysis population definition is also not reported. Enrollment of 4 and early termination do not, by themselves, establish that every planned measure was complete or that all enrolled participants contributed to every outcome.

The record describes the study's termination after none of the subjects could identify traffic location across multiple (4) trials. It does not report a prespecified stopping rule or an interim-analysis plan. The narrative provides a reason for ending the pilot, but does not establish whether the stopping decision followed a formal statistical boundary. Without these details, the effect of early termination on planned inference cannot be quantified.

12. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The adverse-event record lists 4 participants at risk in the Virtual Sound System group. It records 0 participants affected by a serious adverse event and 0 affected by another adverse event. No serious adverse-event terms are listed. Deaths are recorded as null, which is not the same as a reported zero.

These entries are descriptive counts for the enrolled group and the period captured by the registry. They do not show whether events were actively sought at every assessment or how long participants were followed for safety; those details are not reported in the registry record. A zero recorded count in a small pilot does not establish that an event is impossible or that a device is safe in other settings. It means only that the registry reports no affected participants for the event categories with zero entries in this record.

The safety counts should also be kept distinct from the primary performance task. The registry's stopping narrative concerns participants' ability to identify traffic location, not an adverse event. No causal comparison of safety outcomes is available because the design has no control group. The adverse-event entries therefore provide limited descriptive information, not a comparative safety estimate.

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

The record describes a proof-of-concept effort to evaluate virtual sound as an orientation and mobility training tool. It documents the intended task, the performance threshold, and the stopping narrative. In that narrative, the study ended at enrollment of 4 after none of the subjects could identify traffic-vehicle location using the intervention across multiple (4) trials. This is a relevant observation about the task as conducted, but it is not a complete numerical endpoint report.

The record does not report participant-by-participant accuracy, a count meeting the stated criterion, confidence intervals, p-values, or a statistical model. It also does not report a numerical result for the secondary outcome about selecting an appropriate time to cross the street. As a result, the precision and distribution of performance cannot be assessed from the registry record.

The design was single-group, without a like-for-like control arm. Consequently, the observed task experience cannot be attributed solely to the device through a randomized comparison. The record does not establish how the outcome would compare with another training method, with usual practice, or with a different sound system. Nor does the task description establish broader effects on mobility beyond the simulated intersection assessment.

The stated criterion of at least 4 out of five correct responses indicates what the investigators intended to count as efficacy for presenting accurate 3D sound information. It does not establish that the criterion was met or provide an estimate of how often it would be met in a broader population. The termination narrative signals that participants had difficulty with location identification in the pilot, but the lack of a complete numerical result limits more detailed statistical interpretation.

Accordingly, the study is best understood as a small exploratory assessment that generated a stopping observation, not as a definitive comparative evaluation. It neither establishes a quantified benefit nor supports a conclusion about performance in settings or populations not described in the record. Its statistical contribution is primarily the documentation of an early task and its challenges, alongside substantial limits on estimation and inference.

14. Why This Trial Matters Statistically

This trial illustrates a central distinction in biostatistics: a clearly specified outcome is not the same as a fully reported outcome result. The registry describes a concrete task, a response format, a performance threshold, and an assessment schedule. Yet it does not report the numerical participant-level result needed to evaluate the threshold directly. Without that result, readers cannot judge the distribution or precision of task performance from an estimate and interval.

It also shows why design and analysis must be interpreted together. A single-group pilot can describe what happened under its study conditions, but it does not create a randomized counterfactual. The absence of a comparison group limits causal interpretation even if a numerical outcome were available. The early stopping narrative is informative about feasibility, but the registry does not describe a formal stopping rule or interim analysis, so the narrative cannot be treated as a prespecified statistical boundary.

The record also separates planning from evidence. It reports an initial target of 16 subjects based on a power analysis, while the completed enrollment was 4. The original analysis assumptions are not reported. Planning illustrations based on an observed effect use assumptions including equal allocation between two arms, unlike the single-group study design. Such illustrations concern hypothetical future study planning; they do not substitute for an analysis of this pilot or establish observed power.

Finally, the event counts demonstrate the limited scope of safety conclusions in a small study. Zero recorded adverse events is a descriptive finding, not proof that no risk exists. Together, these features make the record useful for understanding measurement, feasibility, reporting, and design constraints, while underscoring why a stopping narrative alone cannot support a precise treatment-effect claim.

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 most direct limitation is the small enrollment: the registry reports 4 participants, although the initial pilot design called for 16. The study ended early after the reported difficulty identifying traffic location. This limits the amount of outcome information available and leaves the original planned analysis unrealized. The registry does not explain whether the target enrollment or the power calculation changed during conduct.

The endpoint description emphasizes a threshold for correct responses, but the registry does not report participant-level results, the number meeting that threshold, or a numerical summary of accuracy. The narrative about inability to identify vehicle location across multiple (4) trials does not show each participant's pattern of responses. The record also lists a secondary outcome but does not report its numerical result.

The single-group design has no control comparison, and masking is listed as NONE. Therefore, the study cannot quantify a difference relative to another intervention, and the record does not establish whether outcome assessment was protected from knowledge of the intervention. Details about assessor procedures, missing observations, analysis populations, and repeated-response handling are not reported in the registry record.

The task used a simulated intersection and a defined sound-based classification response. The record does not report an independent validation measure or establish how performance in this task relates to mobility outcomes beyond the assessment. Generalization beyond the described participants and task is therefore uncertain. The registry's two-year proof-of-concept description also sits alongside start and primary-completion dates both listed as 2009-03; the record does not explain this timing.

Finally, the registry reports no statistical analyses, estimates, intervals, or multiplicity plan. The original power-analysis details and any formal stopping procedure are not reported. These omissions prevent evaluation of inferential precision and make the results primarily descriptive.

16. Related Tutorials

17. Related Statistical Calculators

18. Sources

• ClinicalTrials.gov: Virtual Reality Mobility Training System for Veterans With Vision Loss — NCT00333879.
• Registry record last updated 2013-12-16; status last verified 2013-11.
• Results first posted 2013-11-19.
• 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

The registry record describes NCT00333879, a completed, single-group proof-of-concept study of the Virtual Sound System for veterans with vision loss. Blindness is listed as the condition, and the sponsor is the US Department of Veterans Affairs. Enrollment was 4. The record lists the phase as NA, allocation as NA, and masking as NONE.

The primary outcome assessed accuracy in judging traffic direction at an intersection after training. The task distinguished traffic moving in front of the participant from traffic moving beside them, with a stated criterion of at least 4 out of five correct responses. The record also lists accuracy in selecting an appropriate time to cross the street as a secondary outcome.

The registry says the initial pilot design called for 16 subjects and that the study terminated at 4 subjects after none could identify traffic location across multiple (4) trials. It reports no analyses and provides no complete numerical primary or secondary outcome result. Serious and other adverse events each have 0 participants affected in the enrolled group; deaths are listed as null. The record therefore supports a limited descriptive reading rather than a comparative or precise statistical conclusion.