Influence of intrastromal corneal ring implantation on intraocular pressure measurements using different tonometers in keratoconic eyes.

Purpose: This study aimed to evaluate the influence of intrastromal corneal ring segment implants on the intraocular pressure measurements using Goldmann applanation tonometry, rebound tonometry, and noncontact tonometry in keratoconic corneas and analyze the intertonometer agreement.

Methods: We enrolled 74 eyes in this observational and prospective study. Each participant had a complete eye examination, corneal analysis with Scheimpflug Tomography (Pentacam®), and intraocular pressure evaluation with Goldmann applanation tonometry, rebound tonometry, and noncontact tonometry, before and after intrastromal corneal ring segment implantation (on postoperative days 1, 7, 45, and 90). Intertonometer agreement was assessed using Bland-Altman analysis.

Results: The mean age was 29.9 ± 10.2 years, and 47 (63.5%) eyes had keratoconus grade II. Intraocular pressures were higher for noncontact tonometry preoperatively and on 90 postoperative day (mean ± SD: 12.4 ± 2.2 and 12.1 ± 2.2 mmHg, respectively), followed by Goldmann applanation tonometry (11.1 ± 3.0 and 11.2 ± 2.7 mmHg, respectively), and were lower for rebound tonometry (9.7 ± 3.4 and 9.4 ± 3.2 mmHg, respectively). The variation from the Goldmann tonometry on 7 postoperative day to the baseline (p=0.022) and that of noncontact tonometry on 90 postoperative day to the baseline (p=0.021) were statistically significant. The rebound tonometry underestimated intraocular pressure when compared with the Goldmann applanation tonometry by a mean of 1.47 ± 5.19 mmHg. Noncontact tonometry, when compared with Goldmann applanation tonometry, overestimated intraocular pressure by a mean of 1.23 ± 4.15 mmHg.

Conclusion: Despite statistically significant differences between some postoperative periods, the intraocular pressure measurement differences may not be clinically relevant.