Comparison of Intraocular Pressure Measurement by Goldmann Applanation Tonometry and Pneumotonometry in Healthy Subjects and Patients with Primary Open Angle Glaucoma

Abstract

Objective:To evaluate the role of non-contact Pneumo-tonometry (PT) by comparing intraocular pressure (IOP) measurements with Goldmann Applanation Tonometry (GAT) and PT in healthy subjects, and patients with Primary Open Angle Glaucoma (POAG). Materials and Methods: This prospective comparative study was conducted at PNS Shifa Naval Hospital, Karachi from January 2016 to June 2016. A total of 360 eyes of 180 patients were included, and IOP measurement was done using GAT and PT methods. The difference in readings between the two methods was calculated and analysed using SPSS version 17. Results: A total of 360 eyes were analysed. 90 healthy subjects (180 eyes) and 90 patients with diagnosed POAG (180 eyes) were included. Mean IOP measured in all eyes using GAT and PT was 16.32±5.31 mm of Hg and 18.16±6.76 mm of Hg respectively. Mean difference in IOP was 2.31±1.89 mmHg between two methods, with 278(77.22%) eyes showing higher IOP reading than those measured using GAT. The difference of readings between two methods was statistically significant. The patients with POAG were divided into three groups. Group 1 had IOP less than 15 mm Hg, Group 2 had IOP between 15-25 mm Hg and Group 3 had IOP greater than 25 mm Hg. Mean difference in IOP between two methods was 1.38±1.85, 2.29±2.72 and 3.05±2.68 mm Hg in Group 1,2 and 3 respectively. The mean difference of IOP measurement using GAT and PT in these groups was statistically significant (P<0.001) Conclusion: IOP measurement using PT overestimates the recorded IOP as compared to GAT, and the difference is more pronounced in eyes with higher than normal IOP