180 Degree vs. 360 Degree Selective Laser Trabeculoplasty as Initial Therapy for Glaucoma: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for 180 Degree vs. 360 Degree Selective Laser Trabeculoplasty as Initial Therapy for Glaucoma (NCT02628223), a randomized na study. The primary outcome is Intraocular Pressure (IOP) Measured by Tonometry in Millimeters of Mercury at Three Months of Follow-up.

2. Clinical Question

The registry describes a comparison of two treatment extents, not a comparison of laser treatment with no treatment or with medication. The primary endpoint is a continuous pressure measurement. Its posted group summaries can describe the average pressure in each arm, while the difference and its interval describe the estimated contrast and its uncertainty.

The study’s background says that prior academic-center studies had mixed results and that comparative success-rate data in a community setting were lacking. That describes the motivation recorded for the trial; it does not establish where this trial recruited participants. The setting, detailed participant eligibility rules, and the exact definition of treatment success are not reported in the registry record. The primary outcome is pressure at a fixed follow-up time, rather than a reported binary success rate.

3. Trial Design

The registry classifies the study as randomized, single-masked, and parallel-group, with an enrollment of 76. The two arms received selective laser trabeculoplasty over 180 degrees or 360 degrees. The registry lists a procedure and a Neodymium:Yttrium Aluminum Garnet (YAG) laser device as interventions. It does not state who was masked, how randomization was generated or concealed, or whether masking was maintained throughout follow-up.

The primary endpoint was mean intraocular pressure measured by tonometry at three months. The posted primary outcome summaries include 38 participants in the 180-degree arm and 36 in the 360-degree arm. These are the outcome-specific counts shown in the registry; the record does not explain how these counts relate to overall enrollment or whether any participants lacked an outcome measurement.

The registry lists Temple University as sponsor and labels the trial completed. The recorded start is 2014-09 and the primary completion is 2017-12. The listed conditions span glaucoma-related diagnoses and ocular hypertension, but further detail about the enrolled sample, recruitment sites, clinical setting, and participant flow is not reported in the registry record.

The parallel design assigns participants to one of the two treatment groups for comparison. Randomization is intended, in general, to reduce systematic differences between groups at assignment; it does not ensure that every characteristic is balanced in a trial of this size. The registry does not report baseline group comparisons, the randomization procedure, or an analysis adjusted for baseline pressure or other characteristics. The trial’s original sample-size justification and its planned statistical analysis 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 Intraocular Pressure (IOP) Measured by Tonometry in Millimeters of Mercury at Three Months of Follow-up, measured over 3 months.

The primary endpoint is intraocular pressure measured by tonometry in millimeters of mercury at three months of follow-up. The registry summarizes this continuous measurement with a mean and standard deviation in each arm. The mean describes the group’s average recorded pressure; the standard deviation describes how spread out individual measurements are around that average. It is not itself a measure of how precisely the group mean is estimated.

Pressure is used as the trial’s primary measured outcome because the registry describes selective laser trabeculoplasty as a treatment intended to lower eye pressure in glaucoma. A measurement at a defined follow-up time allows the two randomized groups to be compared on the same type of outcome and timeframe. It does not, by itself, describe every aspect of glaucoma or establish a treatment-success rate.

For the primary result, the 180-degree group had a mean of 20.7 mm Hg with a standard deviation of 5.4, and the 360-degree group had a mean of 19.1 mm Hg with a standard deviation of 4.1. The comparison is expressed as a mean difference, with the 360-degree group contrasted against the 180-degree group. The registry does not report a detailed protocol definition for the measurement procedure, endpoint handling, or clinically important difference.

7. Results Posted in the Registry

• 360 Degrees: mean 19.10 versus 20.70 on control; difference -1.60 (95% CI -3.78 to 0.58), standardized effect d = -0.33; z-test p = 0.150.

8. Secondary Efficacy Endpoints

The registry also posts results for secondary outcomes. For each outcome below, the endpoint type, the test applied to the posted summary statistics, the result and its interpretation are given in turn. Secondary endpoints are usually not adjusted for multiple testing, so they support rather than confirm the primary finding.

Intraocular Pressure (IOP) Measured by Tonometry in Millimeters of Mercury at 1 Year of Follow-up

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • 360 Degrees: mean 19.00 versus 18.70 on control; difference 0.30 (95% CI -1.44 to 2.04), standardized effect d = 0.08; z-test p = 0.736.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between 360 Degrees and the control. The interval gives the range of effects that remain compatible with the data.

Intraocular Pressure (IOP) Measured by Tonometry in Millimeters of Mercury at Time at Which Additional Glaucoma Therapy is Required

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • 360 Degrees: mean 23.70 versus 24.70 on control; difference -1.00 (95% CI -2.67 to 0.67), standardized effect d = -0.27; z-test p = 0.240.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between 360 Degrees and the control. The interval gives the range of effects that remain compatible with the data.

Intraocular Pressure (IOP) Measured by Tonometry in Millimeters of Mercury at Last Follow-up

• Endpoint type: Continuous: a mean value per participant, compared as a difference in means.
• Test: Unadjusted two-sample z-test for the difference in means, using the posted standard deviations.
• Result:
  • 360 Degrees: mean 18.30 versus 18.20 on control; difference 0.10 (95% CI -1.73 to 1.93), standardized effect d = 0.03; z-test p = 0.915.
• Interpretation:
  • The 95% confidence interval includes no difference, so these data do not show a statistically significant difference between 360 Degrees and the control. The interval gives the range of effects that remain compatible with the data.

The registry reports three secondary pressure outcomes, covering one-year pressure, pressure at the time additional glaucoma therapy was required, and pressure at last follow-up. Across these endpoints, the direction of the estimated mean differences is not consistent, and the reported intervals include zero. Taken together, the secondary results do not establish a uniform pattern favoring either treatment extent.

The secondary findings provide context for the primary three-month comparison because they concern the same broad measurement, intraocular pressure, at later or clinically triggered timepoints. They do not replace the primary result: each endpoint addresses a different time or circumstance, and the registry does not report a single combined analysis across these measurements. The endpoint at which additional therapy was required is also conditional on that event, rather than simply a fixed follow-up visit.

Unadjusted secondary comparisons carry less weight as confirmatory evidence. In general, examining multiple outcomes creates more opportunities for chance findings, and p-values that are not adjusted for multiple testing do not account for that process. The registry does not report a multiplicity plan, a prespecified hierarchy for secondary outcomes, or formal analyses for them. It also lists no reported analyses. The secondary outcomes are therefore most appropriately read as descriptive and exploratory evidence alongside the primary result, rather than as independent confirmation.

The registry record lists six outcome measures, while results for three secondary outcomes are posted in addition to the primary result. Details and results for other outcome measures are not reported in the registry record. This incomplete outcome reporting limits assessment of whether the posted outcomes represent the full set of planned comparisons.

Secondary outcomes registered for this trial, for reference (only those above were recalculated):

• Intraocular Pressure (IOP) Measured by Tonometry in Millimeters of Mercury at 1 Year of Follow-up
• Intraocular Pressure (IOP) Measured by Tonometry in Millimeters of Mercury at Time at Which Additional Glaucoma Therapy is Required
• Intraocular Pressure (IOP) Measured by Tonometry in Millimeters of Mercury at Last Follow-up

9. Statistical Interpretation

10. Statistical Methods Explained

The registry reports a continuous primary outcome as a mean and standard deviation for each randomized arm. For the primary endpoint, the reported mean is 20.7 mm Hg for 180 degrees and 19.1 mm Hg for 360 degrees. The standard deviations are 5.4 and 4.1, respectively. A mean gives the central average of the measurements; a standard deviation describes their dispersion around that average. The standard deviation should not be interpreted as a confidence interval for the mean.

What does the mean difference represent?

The posted contrast is defined with the 180-degree arm as the reference and the 360-degree arm as the comparison. The resulting mean difference is -1.6 mm Hg. This sign convention matters: a negative estimate means the observed average in the 360-degree arm is lower than the observed average in the 180-degree arm. It is an estimate of the difference between group means, not a measure of change from baseline; baseline-adjusted results are not reported in the registry record.

In general, a mean difference gives the size and direction of a contrast on the original measurement scale. It is often easier to interpret in the outcome’s units than a standardized effect. The registry also includes standardized effect calculations for planning, but those are not necessary to interpret the primary mean difference. Neither the difference nor the group means alone reveal the distribution of individual responses or establish why the groups differed.

How should the interval be read?

A confidence interval is a range of values compatible with the data under the assumptions of the analysis. In general, narrower intervals indicate greater precision, while wider intervals leave more uncertainty about the estimated effect. The reported primary interval runs from -3.778 to a positive upper endpoint. It crosses zero, so the interval includes both a negative contrast and a positive contrast, as well as a value of no difference. The precise confidence level and the method used to construct the interval are not reported in the registry record.

The interval should be considered alongside the point estimate. The estimate is the single best value in the posted comparison, while the interval conveys uncertainty around it. An interval that includes zero does not prove equality. It means the reported data do not rule out zero under the interval’s assumptions. A claim of equivalence would ordinarily require a prespecified margin and an analysis designed for that question; neither is reported in the registry record.

What does the p-value add?

The unadjusted p-value for the primary comparison is 0.15. In general, a p-value describes how unusual data at least as discordant with a specified null hypothesis would be if that hypothesis and the analysis assumptions were true. It is not the probability that the null hypothesis is true, and it does not measure the probability that the result occurred by chance. It also does not quantify clinical importance. The registry does not report the exact test used, its assumptions, or a prespecified significance threshold for the trial’s own analysis.

The word unadjusted indicates that the reported p-value is not adjusted for multiple comparisons. It should therefore not be treated as if it accounted for testing the primary outcome together with multiple secondary outcomes. The registry lists no reported analyses, and its full analysis plan, including any multiplicity strategy, is not reported in the registry record.

Why can outcome variability affect precision?

In general, the uncertainty in a group mean depends on both how variable measurements are and how many observations contribute. Greater variability can make a mean difference harder to estimate precisely, while more observations can generally improve precision when other assumptions hold. The reported standard deviations describe substantial spread in the primary measurements, and the available outcome counts are 38 and 36. These features help explain why the point estimate should not be read in isolation from its interval.

Over-dispersion is a general concern when observed variability is greater than a model assumes. If an analysis assumes less variation than is actually present, standard errors may be too small and intervals may be too narrow. The registry does not report an over-dispersion assessment or a model for the primary continuous outcome. It would therefore be inappropriate to claim that over-dispersion was present or that a particular adjustment was used.

What analytical details remain unknown?

The registry record does not report whether the comparison used a t-test, regression model, covariate adjustment, or another inferential approach. It also does not report how missing values were handled, whether all randomized participants were analyzed in their assigned arms, whether observations were excluded, or how deviations from treatment assignment were addressed. The comparison is described as unadjusted and is based on the posted summary statistics, but the exact procedure is not documented. These omissions limit independent assessment of model assumptions and the relationship between the registered design and the posted analysis.

General statistical interpretation separates the estimate, its uncertainty, and the assumptions used to obtain both. Here, the estimate is the observed mean contrast, the interval expresses uncertainty, and the p-value provides a test-based summary. None of these alone answers whether the difference is clinically meaningful. That judgment would require a meaningful-difference criterion and context not reported in the registry record.

11. Confidence Intervals and Precision

The primary comparison estimates a mean difference of -1.6 mm Hg, with an interval from -3.778 to a positive upper endpoint. The interval crosses zero, so it does not isolate a difference in one direction. Its width signals uncertainty about the size and direction of the group contrast. The p-value is 0.15, consistent with the fact that the posted comparison does not provide strong evidence against a null difference under the analysis used.

A confidence interval is useful because it shows a range of estimates compatible with the observed data and the method’s assumptions, rather than presenting only a single point estimate. In general, a wider interval indicates less precision. The interval’s exact confidence level and construction method are not reported in the registry record, so those details cannot be independently assessed from the registry entry.

Precision is distinct from clinical importance. The registry does not state what size of pressure difference would matter clinically, and it does not report an equivalence margin. The interval therefore cannot establish whether all clinically important differences have been excluded. Nor does a result that includes zero demonstrate that the treatment extents produce identical outcomes.

The outcome counts of 38 and 36, together with the reported standard deviations, provide context for the uncertainty. The registry does not report missing-data patterns or whether the analysis included all randomized participants. This means the precision reflected in the posted comparison does not necessarily capture uncertainty arising from missing outcomes, analysis choices, or departures from the planned design.

12. Planning a Similar Trial: Sample Size

This is a planning illustration, not a re-evaluation of the original trial. It asks: if a new study wanted to detect a difference like the one observed, or a smaller one, how large would it need to be? It is deliberately not “observed power” of the finished trial, which is not a meaningful quantity.

The planning figures are participants per arm for 80% power and participants per arm for 90% power. They are not total events; the outcome is continuous. The figures are illustrations calculated from the observed effect, not the trial’s original design assumptions. The original sample-size justification is not reported in the registry record.

The stated planning assumptions are a two-sided significance level of 0.05, equal allocation between the two arms, and a normal approximation. Each scenario targets a specified fraction of the observed effect: 100%, 75%, or 50%. The figures estimate how many participants would be needed in each arm under those assumptions to detect the effect used for that scenario at the stated power level.

In general, 80% power means that a study designed under the stated assumptions would have an 80% chance of detecting the specified effect at the stated significance level if that effect were the true one. The 90% column describes the corresponding planning target with a higher chance of detection. These are design concepts, not guarantees about the result of any particular trial. The posted figures are not observed power.

Smaller effects are harder to distinguish from random variation, so planning to detect a smaller fraction of the observed effect requires more participants per arm. The figures are sensitive to the observed estimate used as their starting point. Because an observed effect can be imprecise, these calculations should be treated as planning illustrations rather than as a retrospective judgment of whether the completed trial was adequate.

The curve and listed planning estimates should be read as scenarios conditional on the stated assumptions, not as results from new participants or as evidence that the target effect is clinically important. The registry does not report the assumptions used by investigators when designing the trial, including the effect size they anticipated or the sample size they originally considered necessary.

13. How the Sample Size Is Derived

Power is the probability that a study of a given size rejects the null hypothesis when a specific true effect exists. It depends on four things: the effect to detect, the variability of the outcome, the significance level (here a two-sided α of 0.05, so z_1−α/2 = 1.960) and the desired power (z_1−β = 0.842 for 80% and 1.282 for 90%).

Formula

n is the number of participants in each arm, Δ is the difference in means to detect and σ is the common standard deviation.

Worked calculation for this trial

1. Observed difference Δ = -1.600; pooled standard deviation σ = 4.812.
2. n = 2 × (1.96 + 0.842)² × 4.812² / -1.600² = 142.0, rounded up to 142 participants per arm for 80% power.

The smaller-effect rows in the table above repeat the same calculation with the effect multiplied by 0.75 and 0.5 (for ratios, applied to the logarithm of the ratio).

R code

alpha <- 0.05
z_a   <- qnorm(1 - alpha / 2)          # two-sided
delta <- -1.6                      # observed difference in means
sigma <- 4.81212300110645                     # pooled standard deviation
n_per_arm <- function(power, frac = 1) {
  ceiling(round(2 * (z_a + qnorm(power))^2 * sigma^2 / (delta * frac)^2, 6))
}
for (f in c(1, 0.75, 0.5))
  cat(sprintf("%3.0f%% of observed effect: n per arm = %s (80%% power), %s (90%% power)\n", 100 * f,
              format(n_per_arm(0.80, f), big.mark = ","), format(n_per_arm(0.90, f), big.mark = ",")))

# Check against R's built-in function (t-based, so very slightly larger)
cat("power.t.test:", round(power.t.test(delta = delta, sd = sigma, power = 0.80)$n, 1), "\n")

# Simulation: exact two-sample t-test using simulated means and variances
set.seed(2628223)
n    <- n_per_arm(0.80)
reps <- 20000
m_diff <- rnorm(reps, delta, sigma * sqrt(2 / n))             # difference in sample means
s2     <- sigma^2 * rchisq(reps, 2 * (n - 1)) / (2 * (n - 1))   # pooled sample variance
tstat  <- m_diff / sqrt(s2 * 2 / n)
cat(sprintf("Simulated power at n = %s per arm: %.3f (%d replicates)\n", format(n, big.mark = ","), mean(abs(tstat) > qt(0.975, 2 * (n - 1))), reps))

Output from running the code

100% of observed effect: n per arm = 142 (80% power), 191 (90% power)
 75% of observed effect: n per arm = 253 (80% power), 338 (90% power)
 50% of observed effect: n per arm = 568 (80% power), 761 (90% power)
power.t.test: 143 
Simulated power at n = 142 per arm: 0.799 (20000 replicates)

The simulation draws many sets of group means and variances at the planned sample size and counts how often the two-sample t-test rejects the null. It should land close to the target power; at very small required sample sizes it can fall below it, because the normal approximation is rough there.

14. Multiplicity, Missing Data and Analysis Populations

Multiplicity arises when an analysis tests more than one hypothesis, because the chance of at least one apparently notable result can increase as the number of tests grows. This is a general statistical concern, not evidence that a particular result in this trial is false. The registry distinguishes a primary outcome from secondary outcomes, but the statistical analysis plan and any strategy for controlling multiplicity are not reported in the registry record.

The primary result is accompanied by an unadjusted p-value. The secondary comparisons are also posted without reported analyses or a documented adjustment strategy. It is not reported whether the investigators prespecified a hierarchy, adjusted the significance threshold, or treated secondary endpoints as exploratory. Consequently, the separate p-values should not be interpreted as if they collectively maintained a stated overall error rate.

The registry reports an enrollment of 76 and outcome-specific counts for the posted comparisons, but it does not describe participant flow, missing measurements, exclusions, or reasons for unavailable outcomes. The handling of missing data, including any imputation or sensitivity analysis, is not reported in the registry record. Without this information, the potential for missingness to affect group comparisons cannot be evaluated.

The analysis population is also not described. The registry does not state whether the primary analysis followed intention-to-treat principles, included only participants with observed measurements, or used a per-protocol population. It does not report how treatment changes, protocol deviations, or additional glaucoma therapy were incorporated into analyses. These details matter because analysis choices can affect the meaning and generalizability of an estimated treatment contrast.

The record’s statistical plan, including its handling of repeated or multiple measurements and its approach to baseline values, is not reported. The comparison should therefore be interpreted as the posted unadjusted summary-statistic result, without assuming a particular missing-data, multiplicity, or population strategy.

15. 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 non-serious adverse event terms

The registry records zero serious adverse events among 38 participants at risk in the 180-degree group and zero among 36 at risk in the 360-degree group. It records zero deaths in both groups. For other adverse events, the registry records zero among 38 at risk in the 180-degree group and one among 36 at risk in the 360-degree group.

These counts describe what the registry reports during the recorded safety reporting period; they do not establish that no unrecorded events occurred. The record does not provide a serious-event term because no serious events are listed, and it does not identify the type of the one other adverse event. Timing, severity details, relatedness assessments, and the method used to collect or classify events are not reported in the registry record.

Small event counts provide limited information about uncommon harms. Zero recorded events in these groups should not be interpreted as proof that an event cannot occur. Likewise, the single other event does not establish that the procedure caused it. The safety figures are descriptive registry counts, not a formal comparison demonstrating that one treatment extent is safer.

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

The trial addresses a direct comparative question: mean intraocular pressure at three months after 180-degree versus 360-degree selective laser trabeculoplasty as initial therapy. The observed mean was lower in the 360-degree group, and the estimated difference was -1.6 mm Hg. The interval includes zero, so the posted result leaves uncertainty about whether the underlying average difference is negative, absent, or positive.

This result does not establish that the two treatment extents are equivalent. Equivalence requires a prespecified range of differences considered acceptably small and an analysis designed to evaluate that range. Neither an equivalence margin nor such an analysis is reported in the registry record. Conversely, the observed direction alone does not establish that the 360-degree procedure is superior or that the difference is clinically important.

The primary endpoint measures pressure at one specified follow-up time. It does not, by itself, describe longer-term pressure control, visual outcomes, quality of life, or other aspects of glaucoma care. The registry does report secondary pressure outcomes, but the analysis plan and multiplicity approach are not reported. Those results should therefore be considered in the context of their uncertainty and the broader limitations of registry reporting.

The study’s randomized design supports a comparative question, but the available record does not document the randomization method, masking details, analysis population, missing data, baseline characteristics, or adjusted analyses. These gaps make it difficult to assess potential sources of bias or to judge how broadly the results apply. The trial’s recruitment setting and detailed eligibility criteria are also not reported.

The appropriate statistical reading is restrained: the posted means and comparison describe the observed data, while the interval and unadjusted p-value show that the estimate is uncertain. The result neither proves no difference nor establishes a treatment effect. It should not be used alone to make an individual care decision or to infer outcomes beyond those measured and reported in the registry.

17. Why This Trial Matters Statistically

This trial is statistically useful because it compares two extents of the same procedure rather than comparing different treatment classes. Randomized allocation is relevant to that question: in general, randomization helps make assigned groups comparable in expectation and can support a causal comparison when conduct, follow-up, and analysis are appropriate. The registry does not provide enough methodological detail to assess those conditions fully.

The question also has a practical research rationale in the registry’s background. It describes mixed findings from academic centers and a lack of comparative success-rate data in community settings. That motivation makes the comparison relevant as a question, but the actual setting and a success-rate endpoint are not reported as established features of this trial. Its posted primary endpoint is mean pressure at three months.

The statistical result illustrates why point estimates and uncertainty should be read together. The 360-degree group has a lower observed mean, yet the reported interval includes zero and the unadjusted p-value is 0.15. The point estimate alone might suggest a directional difference; the interval shows why the data do not settle the direction or size of the underlying contrast. Neither a nonsignificant result nor an interval crossing zero proves equivalence.

The study also highlights the importance of transparent reporting. Details on the original sample-size justification, analysis method, missing data, analysis population, multiplicity, and masking are not reported in the registry record. Without them, readers cannot fully evaluate precision, risk of bias, or how confirmatory the secondary results are. The planning illustrations can help show how sample size depends on a target effect, but they are not evidence about the trial’s original design or observed power.

18. 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.

Several limitations are specific to what the registry reports for this trial. Although the study is classified as randomized and single-masked, the method of random sequence generation and allocation concealment is not reported. The identity of the masked group or groups is also not reported. These omissions prevent a detailed assessment of the protection against selection and measurement bias.

The registry does not report baseline pressure, participant characteristics, recruitment sites, or the clinical setting. It lists several glaucoma-related conditions but does not provide detailed eligibility criteria or the distribution of diagnoses across arms. As a result, readers cannot assess baseline comparability from the record or determine how closely the enrolled sample represents a particular clinical population.

Outcome reporting is incomplete for evaluating the full analysis. The registry does not describe participant flow, missing measurements, protocol deviations, treatment adherence, additional therapy handling, or the analysis population. It also does not report the original sample-size justification, detailed statistical methods, or confidence-interval level. These absences limit evaluation of attrition, model assumptions, and whether the posted comparison followed a prespecified analysis.

The primary outcome is pressure at three months, while the secondary outcomes concern later or conditional timepoints. The registry does not report longer-term outcomes beyond those listed, a definition of treatment success, or an equivalence margin. Therefore, the posted pressure comparisons cannot answer every question about durability or clinical relevance. The registry lists six outcome measures but does not report results for all of them. The secondary analysis plan and multiplicity handling are also not reported, which makes secondary findings less suitable as confirmatory evidence.

19. Related Tutorials

20. Related Statistical Calculators

21. Sources

• ClinicalTrials.gov: 180 Degree vs. 360 Degree Selective Laser Trabeculoplasty as Initial Therapy for Glaucoma — NCT02628223.
• Registry record last updated 2020-11-05; status last verified 2020-11.
• Results first posted 2020-11-05.
• 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.

22. Record Summary

The registry describes a completed randomized, single-masked, parallel-group trial of 180-degree versus 360-degree selective laser trabeculoplasty as initial therapy for glaucoma-related conditions. Enrollment was 76. The primary outcome was mean intraocular pressure by tonometry at three months.

The posted primary means were 20.7 mm Hg for 180 degrees and 19.1 mm Hg for 360 degrees. The unadjusted mean difference, 360 degrees minus 180 degrees, was -1.6 mm Hg, with an interval that includes zero and an unadjusted p-value of 0.15. The result is uncertain and does not establish equivalence or superiority.

Three secondary pressure outcomes and safety counts are also reported. The registry does not report the trial’s original sample-size justification, detailed analysis plan, missing-data approach, analysis population, or multiplicity strategy. These gaps limit the strength and scope of conclusions that can be drawn from the posted results.