COMPARISON OF THREE DIFFERENT INTRAOCULAR PRESSURE MEASUREMENT METHODS IN DIFFERENT TYPES OF GLAUCOMA

Comparison of intraocular pressure (IOP) values measured by non-contact tonometry (NCT [Topcon®, Japan]), Corvis ST® (CST [Oculus®, Germany]) and Goldmann applanation tonometry (GAT) in cases with glaucoma.

Cross-sectional study

In this cross-sectional study, cases with primary open-angle glaucoma (POAG), pseudoexfoliative glaucoma (PEG) and pigmentary glaucoma (PG) and healthy volunteers as control group were included. IOP values were measured with CST, NCT and GAT in all cases. Central corneal thickness (CCT) was measured with Corvis ST. The correlation between IOP measurement methods and the relationship of this correlation with glaucoma type and demographic/clinical variables were examined.

Ninety-two eyes of 48 glaucoma patients (29 males, 19 females) with a mean age of 61.1±11.5 years and 55 eyes of 55 volunteers with a mean age of 44.9±9.6 years were included in the study. Twenty-five patients were being followed up with the diagnosis of POAG, 15 patients with PEG, and 8 patients with PG. There was no significant difference between glaucoma and control groups in terms of CCT values (mean 530.2±31.3 micron, 542.1±30 micron, respectively;  p=0.114). Mean IOP values in the glaucoma group were 17.9±4.0 mmHg with NCT, 14.9±4.1 mmHg with GAT, and 17.4±8.1 mmHg with CST (p<0,001). In the POAG cases, GAT and CST (correlation coefficient [cc]=0.851, p<0,001), in the PEG and PG cases GAT and NCT (cc =0.876, p<0.001; cc=0.746, p=0.001, respectively), and in the control group NCT and CST (cc=0.591, p<0.001) measurements showed the strongest correlation. CCT was correlated with NCT in the POAG group (cc:0.306, p=0.037), with CST in the PEG group (cc=0.445, p=0.018), with GAT in the PG group (cc=0.719, p=0.002) and with NCT in the control group (cc =0.254, p=0.075).

The correlation between GAT, which is the gold standard method for measuring intraocular pressure, and other intraocular pressure measurement methods may differ depending on the type of glaucoma. In our study, the most consistent measurements with GAT were obtained with CST in patients with POAG and with NCT in other glaucoma types. The relationship between CCT and IOP measurements may vary depending on the measurement method and glaucoma type.