Effectiveness of 4 tonometers in measuring IOP after femtosecond laser–assisted LASIK, SMILE, and transepithelial photorefractive keratectomy

Abstract

Purpose: 

To test the performance of 4 tonometers in estimating intraocular pressure (IOP) after 3 forms of refractive surgery.

Setting: 

Eye Hospital, Wenzhou Medical University, China.

Design: 

Prospective case series.

Methods: 

Patients matched for preoperative age, corneal thickness, and myopic correction enrolled for femtosecond laser–assisted laser in situ keratomileusis (FS-LASIK), small-incision lenticule extraction (SMILE), or transepithelial photorefractive keratectomy (tPRK) were included in the study. For each patient, 4 measurements of IOP were obtained preoperatively and 3 months postoperatively, using the Goldmann applanation tonometer (GAT-IOP), the Dynamic Contour Tonometer (DCT-IOP), corneal-compensated IOP (IOPcc) from the Ocular Response Analyzer, and biomechanically corrected IOP (bIOP) from the Corvis ST. Overall corneal stiffness was also estimated based on the stiffness parameter (SP-A1) provided by the Corvis ST.

Results: 

The study included 144 eyes of 144 patients. Among the 3 procedures, the smallest variances between preoperative and postoperative IOP estimates and SP-A1 values were observed with the tPRK, followed by SMILE and FS-LASIK. In the tPRK group, no significant differences were observed in both bIOP (−0.18 ± 1.63 mm Hg) and DCT-IOP (−.64 ± 2.34 mm Hg), whereas they were larger and significant in GAT-IOP (−1.78 ± 2.29 mm Hg) and IOPcc (−2.77 ± 1.84 mm Hg). In FS-LASIK and SMILE groups, although there were similar significant reductions in IOP postoperatively, these reductions were still lower in bIOP and DCT-IOP than those in GAT-IOP and IOPcc.

Conclusions: 

The bIOP and DCT-IOP were the least affected IOP estimates between the 3 refractive surgery procedures considered. It was evident that tPRK produced significantly smaller reductions in IOP readings than did FS-LASIK and SMILE.

In Brief

Biomechanically corrected intraocular pressure and DCT-IOP were the least affected IOP measurements by refractive surgeries. Reductions in IOP measurements were lower after tPRK than those after FS-LASIK and SMILE.