Comparison of the precision of air puff tonometer with the gold standard Goldmann applanation tonometer and Schiotz tonomter in Egyptians

Purpose The aim of this study was to determine the accuracy of the air-puff tonometer compared to the Goldmann applanation tonometer (GAT) and Schiotz tonometer. Patients and methods This is a descriptive, cross-sectional prospective study that included 410 eyes of 205 patients who attended the General Outpatient Clinic in Port Said Specialized Ophthalmology Hospital, Port Said, Egypt. The intraocular pressure (IOP) was measured with air-puff tonometer, then GAT and Schiotz tonometer, respectively. Pachymetry was done in all patients. Results The mean age of the patients was 51.37±16.35 years (range=18–79 years), with 62.4% of them being 50 years or more. Of the studied cases, 61.4% were females and 38.6% were males. The mean central corneal thickness was 549.09±36.23 µm in the right eyes and 551.04±38.26 µm in the left eyes. The mean air-puff tonometer IOP was 19.70±3.63 mmHg in the right eyes compared to 18.46±3.13 and 17.82±3.85 mmHg as measured by the GAT and Schiotz tonometer, respectively. On the other hand, the mean left eyes air-puff tonometer IOP was 20.09±3.49 mmHg compared to 18.65±3.27 mmHg by the GAT and 18.09±3.90 mmHg by the Schiotz tonometer. There was a statistically insignificant correlation between the IOP and age in both eyes. On the other hand, there was a statistically significant correlation between the IOP and sex with females having higher IOP values in both eyes, as measured by all tonometers, than males except for the right eyes in the Schiotz’s IOP values, which were insignificant. The mean IOP values for all tonometers were slightly higher in the left eyes than in the right eyes. In both eyes, the correlation values between the GAT and the air-puff tonometer were greater than 0.8, indicating a strong correlation. Additionally, the Bland–Altman analysis revealed more agreement between the GAT and the air-puff tonometer than the Schiotz tonometer. Conclusion The values measured by the air-puff tonometer were accurate and approximately close to the values measured by the GAT. So, we can rely on the air-puff tonometer measurements especially in rural areas and during epidemics. Also, we can depend on the Schiotz tonometer values when we use it for patients under general anesthesia or when the GAT and air-puff tonometer are not available.