A brief history of the evolution of tonometers and comparison of goldmann applanation tonometer versus non–contact tonometer and their correlation to central corneal thickness

Abstract

: This study was designed to evaluate and compare differences between Goldmann applanation tonometer’s (GAT) values and non-contact tonometer’s (NCT) values In various central corneal thickness(CCT).: This prospective study of 100 eyes of 50 subjects was done for the age group of 25 yrs – 75 yrs, who did not have any glaucomatous changes in the optic disc. Intraocular pressure readings were taken by GAT and NCT was measured within a fixed time range of 10:00 AM to 1:00 PM to minimize the effect of diurnal variation. CCT and NCT readings were measured by NIDEK 530P while GAT was performed by Appasamy ref AATM-K001 after 20 minutes and was recorded from both eyes of 50 subjects. Then the CCT effect was correlated with the intraocular pressure values, which were obtained by GAT and NCT.: The data were recorded from 100 eyes of 50 subjects, of whom 24 were females and 26 were males.The mean age was 51.22 ± 2.7 years, while the mean CCT value was 530.6 ± 5.7 µ.The mean IOP values respectively for NCT and GAT were 15.41 ± 0.6 mmHg, and 15.11 ± 0.5 mmHg, respectively (Table 1). The data shows a significantly strong positive correlation between NCT and CCT (r= 0.73, P< .0001), and a strong positive correlation between GAT and CCT (r= 0.55, P< .0001) (Table 2, 5 and 6).The Pearson coefficient value between NCT and GAT was also strong (r = 0.76, P< .00001)(Table 3). The findings in our study correlate with earlier research. It demonstrates that, with the application of appropriate correction factors for CCT, NCT can be considered a good screening tool for the measuring Intraocular pressure.