Reliability and reproducibility of intraocular pressure measurements using the Goldmann applanation tonometry in glaucoma suspects

Abstract

Aims: This study aimed to examine the intra-observer reliability of three ophthalmologists who measured intraocular pressure (IOP) using the Goldmann applanation tonometry (GAT) and the inter-observer variability among them during three visits of glaucoma suspects. Methods: This prospective observational study evaluated the reliability and consistency of the IOP measurements made by three trained observers using the GAT. The three observers recorded IOP readings for 100 patients during three visits; both the right and left eyes of the patients were examined during these visits. Each observer calculated inter-observer and intra-observer variation as intraclass correlation coefficient (ICC). To determine the reliability, Cronbach’s alpha was calculated. A P value of <0.05 was considered significant. All statistical analyses were performed using Statistical Package for the Social Sciences (SPSS-22). Results: A total of 1,800 IOP readings were taken by three observers (600 IOP readings by each). In regard to the calculated values, Cronbach’s alpha for each pair was found to be above 0.9. For the assessment of intra- and inter-observer variability, the calculated value of the ICC for each pair was >0.9, and the overall ICC was also >0.9. The results showed excellent inter- and intra-observer reliability for the observers. Conclusion: The IOP values measured using the GAT were found to have significant intra- and inter-observer reliability. This demonstrates that ophthalmologists can perform valid and reliable IOP assessments. This also indicates the importance of careful and proper training of observers in measuring IOP using the GAT and the standardisation of criteria for early detection of glaucoma.