Intraocular Pressure Before and After Corneal Refractive Surgery: A Prospective Comparison of Corvis ST and Ocular Response Analyzer

Abstract

Prcis: The study showed that Corvis ST's biomechanical intraocular pressure (bIOP) and ocular response analyzer's (ORA) cornea-compensated intraocular pressure (IOPcc) do not agree well, before or after photorefractive keratectomy (PRK), and may not be used interchangeably. bIOP remained unchanged after PRK.

Objective: To evaluate the agreement between the biomechanically corrected intraocular pressure (bIOP) measured by the Corvis ST and the IOPcc measured by the ORA before and after PRK.

Patients and methods: In this prospective interventional study, a total of 53 patients (53 eyes) were included. Measurements were acquired using both the Corvis ST and ORA devices before and 3 months post-PRK. The agreement between the 2 devices was evaluated using limits of agreement (LoA) and Bland-Altman plots.

Results: The participants had a mean age of 29.6 ± 5.21 years (range: 21 to 40), with 41 (77.4%) of them being females. After the surgery, the average change in intraocular pressure (IOP) was 0.3 ± 1.7 mm Hg for bIOP and -1.6 ± 4.0 mm Hg for IOPcc. The corresponding 95% LoA were -3.5 to 4.2 mm Hg and -9.5 to 6.3 mm Hg, respectively. The 95% LoA between bIOP and IOPcc after PRK was -2.3 to 8.5 mm Hg. Notably, the bIOP values were higher for IOPs <20 mm Hg and lower for IOPs >20 mm Hg compared with IOPcc.

Conclusions: The findings indicate a weak agreement between the Corvis ST-bIOP and the ORA-IOPcc both before and after PRK. These devices may not be used interchangeably for IOP measurement. bIOP exhibited less variation compared with the IOPcc, suggesting that the bIOP may be a better option for IOP reading after PRK.