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April 19, 2026BMC Ophthalmology0 citationsOpen Access

Comparison of intraocular pressure measured by Goldman applanation tonometer, noncontact tonometer and trans-palpebral tonometer

MTMadhu ThapaGAGautam Pragati AdhikariGSG. C. Saroj

Key Points

  • To evaluate the reliability and agreement of NCT and TPT compared with GAT in measuring intraocular pressure.
  • Measured intraocular pressure using GAT, NCT, and TPT on 224 eyes from 112 patients.
  • Performed statistical comparisons using Friedman test and post hoc pairwise Wilcoxon tests.
  • Assessed reliability using Cronbach’s alpha and intraclass correlation coefficient (ICC).
  • Evaluated agreement using Bland–Altman plots and Spearman’s rank-order correlation.
  • Median intraocular pressure readings were 14 mmHg for GAT and NCT, and 15 mmHg for TPT.
  • Statistically significant differences found among the three methods (p < 0.001).
  • Cronbach’s alpha indicated acceptable internal consistency at 0.691.
  • Moderate reliability was suggested by an ICC of 0.668 (p < 0.001).
  • Good agreement between GAT and NCT, while TPT showed wide limits of agreement with GAT.

Abstract

To evaluate reliability and agreement of non-contact tonometry (NCT) and trans-palpebral tonometry (TPT) compared with Goldmann-applanation tonometry (GAT). A total of 224 eyes from 112 patients were included between January and April 2025. Intraocular pressure (IOP) was measured using GAT, NCT, and TPT. Comparison among the three measurement groups were performed using the related-samples Friedman test. Post hoc pairwise comparisons were conducted using the Wilcoxon signed-rank test with Bonferroni correction. Reliability was assessed using Cronbach’s alpha and the intraclass correlation coefficient (ICC). Agreement between methods was evaluated using Bland–Altman plots and Spearman’s rank-order correlation. Median IOP were 14 mmHg for GAT, 14 mmHg for NCT and 15 mmHg for TPT. Friedman’s ANOVA showed a statistically significant difference among three methods (χ² = 40.652, p < 0.001). TPT readings differed significantly from both GAT and NCT (p < 0.001). The difference between GAT and NCT was not significant (p = 0.024) because it did not meet the Bonferroni-adjusted threshold (α = 0.017). Cronbach’s alpha was 0.691, indicating acceptable internal consistency. The ICC for average IOP was 0.668 (95% CI: 0.571–0.743, p < 0.001), suggesting moderate reliability. Spearman’s correlation showed moderate-agreement between GAT and NCT (ρ = 0.586, p < 0.001), weak-agreement between TPT and NCT (ρ = 0.315, p < 0.001), and no correlation between GAT and TPT (ρ = 0.090, p = 0.177). Bland-Altman analysis confirmed good-agreement between GAT and NCT, fair-agreement between NCT and TPT, and poor-agreement between GAT and TPT. GAT and NCT showed comparatively better agreement, whereas TPT demonstrated wide limits of agreement with GAT and should not be used interchangeably for clinical decision-making; TPT may be considered only for preliminary screening when contact tonometry is not feasible.

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Cite This Study

Thapa et al. (2026) studied this question.

synapsesocial.com/papers/69e47376010ef96374d8f4a3https://doi.org/10.1186/s12886-026-04821-w
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