Effectiveness of the Goldmann Applanation Tonometer, the Dynamic Contour Tonometer, the Ocular Response Analyzer and the Corvis ST in Measuring Intraocular Pressure following FS-LASIK

Purpose: To test the performance of the four tonometers in providing IOP measurements that were free of the effects of corneal biomechanics changes caused by refractive surgery.Methods: Four tonometers were employed to provide IOP measurements for 65 participants who accepted Femtosecond laser-assisted LASIK (FS-LASIK). The measurements included GAT-IOP by the Goldmann Applanation Tonometer, DCT-IOP by the Dynamic Contour Tonometer, Goldmann-correlated IOP (ORA-IOPg) and corneal-compensated IOP (ORA-IOPcc) by the Ocular Response Analyzer, and uncorrected IOP (CVS-IOP) and biomechanically corrected IOP (CVS-bIOP) by the Corvis ST. Statistical analyses were performed to assess the association of the differences in IOP caused by FS-LASIK with central corneal thickness (CCT), mean corneal curvature (Km), age, refractive error correction (REC), optical zone diameter (OZD), ablation zone diameter (AZD), residual stromal bed thickness (RSB) and RSB ratio (RSB/CCT). Multiple linear regression models were constructed to explore factors influencing IOP changes.Results: All four tonometers exhibited significant differences between IOP measurements taken pre and post-surgery except for CVS-bIOP in the low to moderate myopia group (t = 1.602, p = .12). CVS-bIOP, followed by DCT-IOP, provided the best agreement between pre and post-FS-LASIK measurements with the lowest differences in IOP and the narrowest limits of agreement. The pre-post IOP differences were also significantly associated with the reduction in CCT in only GAT-IOP, ORA-IOPg, and CVS-IOP. CVS-bIOP and ORA-IOPcc were the only measurements that were not correlated with CCT, Km or age both before and after FS-LASIK.Conclusions: The biomechanically corrected bIOP from the Corvis ST provided post-FS-LASIK measurements that were in closest agreement with those obtained before surgery. In comparison, GAT-IOP, ORA-IOPg, ORA-IOPcc, and CVS-IOP appeared to be more influenced by the changes in corneal biomechanics caused by FS-LASIK.