Comparison between different tonometers following intrastromal corneal ring segments implantation

Purpose: To compare different intraocular pressure (IOP) readings in corneas with intrastromal corneal ring segments (ICRS) taken by three different tonometers; Goldmann applanation tonometry (GAT), air puff tonometer, and ocular response analyzer (ORA) corneal-compensated IOP (ORA-IOPcc) and determine the relation of these measurements to different corneal parameters taken by Pentacam. Methods: An observational cross-sectional analytic study included patients who underwent ICRS keraring implantation at 3 months. In each eye, the two rings were placed using the femtosecond laser assisted technique 5.5 or 6 mm from the center. IOP was measured using three different tonometers; GAT, air puff tonometer, and ocular response analyzer (ORA) corneal-compensated IOP (ORA-IOPcc). Results: Fifty eyes of 30 patients (20 males and 10 females) aged 27.56 +/- 6.38 years were included. IOP measurements by GAT, air puff tonometer, and ORA-IOPcc were 13.28 +/- 2.13 mmHg, 10.47 +/- 2.55 mmHg, and 13.19 +/- 2.78 mmHg, respectively. Comparisons between air puff and each of GAT and ORA-IOPcc were statistically highly significant (p-value <0.001). Conclusion: IOP measurements taken by air puff tonometer were significantly lower than those taken by GAT and ORA-IOPcc. These differences were not constant across the pressure range but increased as the pressure values determined using GAT and ORA increased. ORA-IOPcc and GAT showed similar readings. No correlation was found between any of the IOP readings taken by the three tonometers and the central corneal thickness.

Automated summary

In comparing different tonometers for measuring intraocular pressure in corneas with intrastromal corneal ring segments, it was found that the air puff tonometer provided significantly lower readings compared to GAT and ORA-IOPcc. Additionally, there was no correlation between the IOP readings from the tonometers and central corneal thickness.