Effects of Blue-light Blocking Lens on Visual Functions: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Effects of Blue-light Blocking Lens on Visual Functions (NCT02821403), a non-randomized na study. The primary outcome is Contrast Sensitivity as Assessed by Mars Contrast Sensitivity Chart.

2. Clinical Question

The stated purpose is to determine and compare visual performance after wearing blue-light blocking lenses in participants with and without presbyopia. The planned assessments also include accommodative response, color vision, and questionnaires about quality of life, vision, and lens performance. The working hypothesis in the brief summary states that the blue-light blocking lens has no effect on these measures.

The registry lists an enrollment of 80, while the brief summary describes a plan to recruit 160 computer users. The record does not clarify the relationship between those figures or report the number who completed the study or contributed outcome data. It also does not report contrast-sensitivity estimates for any lens or group. Consequently, the clinical question is identifiable, but the posted record does not establish what was observed or how precisely the lens groups differed.

3. Trial Design

The registry describes a completed, parallel, non-randomized study with single masking. The sponsor is The Hong Kong Polytechnic University. The record lists an enrollment of 80 and study dates from 2014-07 to 2015-05. Phase is recorded as NA. The identity of the masked party is not reported in the registry record.

Two participant groups are described: young adults without presbyopia, aged 18-35 years, and middle-aged adults with presbyopia, aged >40 years. The brief summary describes computer users with use of >2 hours/day. It says three pairs of ophthalmic lenses were to be prescribed, including the blue-light blocking lens, with different intended viewing distances for the two participant groups. It also describes an adaptation period of 1 month for each pair. These are descriptions of the plan; the record does not report adherence, actual exposure, or completion of each adaptation period.

The listed devices are a clear lens with regular coating, a regular-coating lens with yellow tint, and a clear lens with blue-light blocking coating. Although the brief describes pre- and post-treatment measurements and repeated lens use, the registry classifies the study as non-randomized. It therefore does not support interpreting the lens groups as randomized arms or as a like-for-like control comparison. The record does not report how lens order was assigned or whether each participant received every lens.

The primary endpoint is contrast sensitivity assessed at every 1-month interval from the date of randomization, up to 3 months. That timeframe wording sits alongside the non-randomized allocation classification; the record does not explain the discrepancy. The number of analyzed participants, outcome data by group, and analysis populations 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.

"First Intervention (1 Month)"

"Second Intervention (1 Month)"

"Third Intervention (1 Month)"

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 Contrast Sensitivity as Assessed by Mars Contrast Sensitivity Chart, measured over Every 1-month interval from the date of randomization, up to 3 months.

The primary endpoint is contrast sensitivity measured with the Mars Contrast Sensitivity Chart and expressed as a log contrast sensitivity score. The registry describes reading letters from higher to lower contrast; testing ended after two consecutive errors. The score was based on the last correct letter, with a deduction for prior errors. The chart was placed at 50 cm, and the record says one of three charts with different letter combinations was selected randomly to reduce memorization.

Measurements were described under normal room illumination of 400 lux and under glare. For the glare condition, a brightness acuity tester at its medium light intensity level of 100 foot lamberts was used. The timeframe is every 1-month interval from the date of randomization, up to 3 months. The registry describes the endpoint parameter as a mean and its dispersion as a standard error. It states that a higher mean indicates improved contrast sensitivity.

Contrast sensitivity is used to assess the ability to distinguish differences in contrast, rather than simply to identify high-contrast details. Measuring it under normal and glare conditions allows the endpoint to describe performance in both specified testing conditions. This is a general explanation of the measure, not a finding from the study. The registry record does not report the mean scores, standard errors, participant counts at each assessment, or comparisons among lenses and participant groups. It also does not report how results from the two lighting conditions were combined, if they were combined.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

What does the endpoint summarize? The primary measure is a continuous score, and the registry specifies a mean as its summary. A mean describes the central level of the measured scores. The standard error describes the precision of an estimated mean: in general, a smaller standard error indicates a more precisely estimated mean, while a larger standard error indicates more uncertainty. A standard error is not the same as the spread of individual scores. These are general statistical explanations; the registry record does not give observed means or standard errors for this study.

The record describes the score as the log contrast sensitivity of the last correct letter, with a deduction of 0.04 log unit for every prior error. It specifies testing under normal room illumination and under glare. The stated timeframe is every 1-month interval from the date of randomization, up to 3 months. A repeated schedule can describe change over time, but the registry record does not specify the statistical model used to analyze repeated measurements, how within-participant correlation was handled, or whether measurements were summarized separately by condition, time, lens, or participant group.

Why does the allocation matter? The study is classified as non-randomized. In general, random allocation can help balance participant characteristics across treatment groups, while non-randomized comparisons may be affected by differences in who receives or uses each treatment. Here, the record explicitly warns that the arms are not a like-for-like control comparison. It does not report an adjustment strategy or enough results to assess whether any observed differences were controlled for participant characteristics. The brief summary describes different intended viewing distances for participants with and without presbyopia, which is another reason not to treat those participant groups as interchangeable.

The registry lists three lens devices and describes an adaptation period of 1 month for each pair. It does not report the order in which lenses were used or how that order was determined. In general, lens order can matter in repeated-measurement designs if learning, carryover, or changes over time affect scores. The record does not say whether these possibilities were assessed. The timeframe's reference to randomization also does not resolve this issue because the study allocation is classified as non-randomized.

What can confidence intervals and p-values tell a reader? In general, a confidence interval expresses uncertainty around an estimated effect and shows a range of values compatible with the data under the method used. A p-value summarizes how compatible the data are with a specified null hypothesis under a statistical model; it does not measure the size or importance of an effect. Neither type of statistic is reported for the primary endpoint in the registry record. Without an estimate and its uncertainty, the direction, magnitude, and precision of the result cannot be assessed.

The registry names the endpoint summary as a mean with standard error, but does not report a comparison method, a confidence level, a hypothesis-testing procedure, covariates, or a model for repeated observations. The statistical analysis plan is not reported in the registry record. It is therefore not possible to determine whether any reported result, if available elsewhere, would be adjusted or unadjusted, or what assumptions would underlie its uncertainty estimate.

What do the planning assumptions mean? The sample-size assumptions describe an illustration computed from the observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. In general, a planning calculation estimates the number of participants needed under chosen assumptions to target a specified power for detecting an effect. Rows described as planning for a fraction of an observed effect represent alternative assumptions about the effect size. These are planning illustrations, not observed power, and they do not establish that a study had adequate precision or that an effect was present. The underlying observed effect is not reported in the registry record, so the planning assumptions cannot be independently interpreted against reported trial results.

Over-dispersion is a general concern when the variability in observed data exceeds what a statistical model assumes. If present and not accounted for, uncertainty can be understated. The registry record does not report an analysis model or dispersion assessment, so it is not possible to determine whether over-dispersion was relevant. More broadly, the record does not report the analysis population, the handling of missing measurements, or results for the named endpoint. Statistical methods beyond the descriptive endpoint specification are therefore not established by this record.

10. Multiplicity, Missing Data and Analysis Populations

The registry identifies contrast sensitivity as the primary outcome and lists self-assessment of lens performance through a questionnaire as a secondary outcome. It also reports three outcome measures, but the other measures are not identified in the listed outcomes. The brief summary describes accommodative response, color vision, quality of life, vision, and lens-performance questionnaires. The record does not clarify how these measures map to the outcome-measure count or which were designated as primary or secondary beyond the named contrast-sensitivity endpoint.

When a study examines multiple outcomes, conditions, timepoints, or groups, the chance of at least one apparently unusual finding can increase. General approaches to address multiplicity include prespecifying a hierarchy, adjusting tests, or interpreting estimates with suitable caution. The statistical plan, any multiplicity adjustment, and any hierarchy among contrast-sensitivity conditions and timepoints are not reported in the registry record. The presence or absence of such procedures cannot be inferred.

The registry does not report missing-data counts, reasons for missingness, completion at each assessment, or the method used to handle incomplete measurements. It also does not define an analysis population, such as which participants or observations were included in each outcome analysis. The enrollment entry and the recruitment figure in the brief summary differ, and the record does not explain the relationship between them. These gaps limit assessment of how missing information or participant inclusion could affect the results.

Adverse-event entries list zero participants at risk and zero affected for serious and other events in both participant groups. With no participants recorded as at risk, these entries do not establish that no adverse events occurred among participants who used the lenses. The registry record does not provide further adverse-event detail.

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

The record establishes that a study was registered to examine visual performance with three types of ophthalmic lenses, including a blue-light blocking lens. It describes contrast sensitivity as the primary endpoint and specifies measurements under normal and glare conditions. It also identifies participant groups with and without presbyopia and describes a planned schedule of lens use and assessment.

Those descriptions do not establish the study’s findings. The registry record does not report contrast-sensitivity scores, lens comparisons, estimates of change, or uncertainty measures. It therefore does not show whether scores differed by lens, whether they changed over time, or whether any observed pattern varied by presbyopia status or lighting condition. The stated hypothesis and the definition that a higher mean indicates improved sensitivity are not results.

The design classification is non-randomized, and the registry warns that the arms are not a like-for-like control comparison. Accordingly, even if differences were available, a comparison would need to be interpreted in light of possible group differences and the allocation process. The record does not report an adjustment strategy or enough information to assess those issues.

The record also cannot support a conclusion about the practical importance of any contrast-sensitivity difference because it gives no estimated effect or measure of uncertainty. Nor does it establish the absence of adverse events: the adverse-event entries record zero at risk in each group. The registry’s planned sample-size illustrations are not evidence of observed power or of a treatment effect.

In general, an endpoint can be clinically relevant without a registry record reporting its outcome. The distinction is important: the study question and measurement procedures are described, but the posted information does not provide the data needed to judge the observed result. No medical advice or treatment conclusion follows from the information in this record.

12. Why This Trial Matters Statistically

This study is statistically notable for the gap between a clearly described measurement procedure and the absence of posted outcome estimates. The registry explains how contrast sensitivity was assessed, including the chart, scoring approach, testing distance, and normal and glare conditions. Yet without means, standard errors, or comparisons, the measurement description cannot answer whether scores differed or how precise any estimated difference was.

The non-randomized allocation is central to interpretation. The registry itself cautions that the arms are not a like-for-like control comparison. This highlights a general principle: a numerical difference between groups is not automatically an effect of the treatment when allocation may leave groups systematically different. The record does not report analyses that would address such differences, and it provides no outcome estimates to evaluate.

The record also illustrates why design details and registry entries need to be read together. The timeframe refers to assessments from the date of randomization, while the allocation is classified as non-randomized. The enrollment entry of 80 differs from the planned recruitment of 160 described in the brief summary. The record does not resolve either inconsistency. These discrepancies should not be silently reconciled by assuming a particular actual design or recruitment history.

Finally, planning calculations and observed findings answer different questions. The stated assumptions describe planning illustrations based on an observed effect, but no effect estimate is reported in the registry record. Those calculations cannot replace an analysis of the observed data. For statistical interpretation, transparent reporting of participant flow, analysis methods, estimates, and uncertainty would be needed to connect the measurement plan to a conclusion.

13. 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, so the observed contrast-sensitivity level and any comparison among lenses cannot be assessed. It also does not report standard errors, confidence intervals, p-values, or participant counts contributing to the outcome at each assessment. The precision and completeness of the primary endpoint are therefore unknown.

The study is classified as non-randomized, and the record cautions that the arms are not a like-for-like control comparison. It does not describe how participants were assigned to lens conditions, whether lens order was controlled, or whether analyses adjusted for group differences. The brief summary describes different viewing distances for participants with and without presbyopia, making direct comparison of those populations especially difficult to interpret without further analysis details.

The record’s enrollment entry is 80, while the brief summary describes a planned recruitment of 160. The number actually recruited, completing the study, and analyzed is not reported in the registry record. The endpoint timeframe refers to randomization despite the non-randomized classification; the record does not explain this wording. These unresolved details make the implemented study difficult to reconstruct.

The record does not report adherence, lens-use order, missing-data handling, analysis populations, or the statistical model. It also does not identify all three outcome measures counted in the record or explain how multiplicity was handled. Adverse-event entries list zero at risk, limiting interpretation of the listed zero affected counts. Together, these limitations mean the registry describes the intended question and measurement procedures more fully than it documents execution, analysis, and results.

14. Related Tutorials

15. Related Statistical Calculators

16. Sources

• ClinicalTrials.gov: Effects of Blue-light Blocking Lens on Visual Functions — NCT02821403.
• Registry record last updated 2017-04-07; status last verified 2016-06.
• Results first posted 2017-04-07.
• 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.

17. Record Summary

The registry record describes a completed, parallel, non-randomized, single-masked study of ophthalmic lenses in adults with and without presbyopia. It lists an enrollment of 80, a study period from 2014-07 to 2015-05, and The Hong Kong Polytechnic University as sponsor. The brief summary describes planned recruitment of 160 computer users and lens use over adaptation periods of 1 month.

Three devices are listed: a clear lens with regular coating, a regular-coating lens with yellow tint, and a clear lens with blue-light blocking coating. The primary outcome is mean log contrast sensitivity measured with the Mars Contrast Sensitivity Chart under normal and glare conditions, at every 1-month interval from the date of randomization, up to 3 months.

Primary outcome estimates and the statistical analysis plan are not reported in the registry record. The allocation is non-randomized, and the record cautions that the arms are not a like-for-like control comparison. The enrollment and planned recruitment figures are not reconciled, and the record does not report the analyzed sample or outcome completeness.