INTRODUCTION: To investigate and compare the reliability Goldmann applanation tonometer (GAT), Dynamic contour (DCT), and Non-contact (NCT) tonometers in intraocular pressure (IOP) measurement and the affecting parameters in healthy subjects and cases with primary open-angle glaucoma (POAG).
METHODS: Left eyes of 64 cases (32 males and 32 females) were selected for this prospective, controlled study. Thirty-three cases had POAG, and 31 subjects were selected as control. IOP measurement was performed with NCT, DCT, and GAT consecutively for each patient, and then central corneal thickness (CCT) was measured. Ocular pulse amplitude (OPA) and all values were recorded.
RESULTS: The mean age was 53.36±10 years (31-80), and CCT was 561±45μ. IOP was found 16.39±3.75 mmHg with GAT, 17.89±3.55mmHg with DCT, and 15.76±3.49mmHg with NCT. The difference between DCT with NCT and GAT was significant. While there was a positive correlation between CCT with all three methods, the weakest one was with DCT. While the correlation between all three methods was excellent, it was found to be the strongest between DCT and GAT. Thick corneas affected all three methods, but DCT was the least affected. While DCT tends to measure higher than both GAT and NCT, this difference decreased as the corneal thickness increased. OPA was found to be 2.56±1.04 mmHg; no statistical difference was found between the groups. There was a correlation between OPA and IOP, and OPA was significantly higher in women.
DISCUSSION AND CONCLUSION: DCT is minimally affected by corneal factors, especially in thin corneas, and shows excellent correlation with GAT. This new generation digital tonometer can be used safely in glaucoma diagnosis and follow-up.