Comparison between the values of intra-ocular pressure measured by Goldmann applanation tonometer and Air-Puff non-contact tonometer and their relationship with central corneal thickness.

Glaucoma is a sight threatening disorder in which measuring intra-ocular pressure (IOP) with accuracy plays a fundamental role. This study aimed to compare the IOP values air-puff of non-contact tonometer(APT) and Goldmann applanation tonometer (GAT) along with their relationship to central corneal thickness (CCT), in various IOP groups. Three hundred and eleven patients were enrolled using convenience sampling in this cross-sectional, prospective study. IOP was measured with Keeler 3000 APT and GAT along with CCT using TOMEY EM-4000. Data was analysed using Bland-Altman, Spearman's and intra-class correlation analysis of APT, GAT and CCT on SPSS 24.0. The median IOP by APT and GAT was 14 mmHg (range:37) and 12 mmHg (range:16) whereas the median CCT was 534µ (range: 44), respectively. At low (<10 mmHg) and normal IOP (10-20 mmHg) both the instruments showed similar results but GAT was found to be more accurate (p£0.001) at higher IOP (21-30 mmHg). However, at moderate and higher groups of IOP, APT revealed overestimation of IOP compared to GAT. CCT also plays a significant role.