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

Abstract

Precis: The study showed that Corvis ST’s bIOP and ORA’s IOPcc do not agree well, before or after PRK, and may not be used interchangeably. bIOP remained unchanged after PRK. Purpose: To evaluate the agreement between the biomechanically-corrected intraocular pressure (bIOP) measured by the Corvis-ST and the cornea-compensated IOP (IOPcc) measured by the Ocular Response Analyzer (ORA) before and after photorefractive keratectomy (PRK). 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 two 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 female. Following the surgery, the average change in IOP was 0.3±1.7 mmHg for bIOP and −1.6±4.0 mmHg for IOPcc. The corresponding 95% LoA were −3.5 to 4.2 mmHg and −9.5 to 6.3 mmHg, respectively. The 95% LoA between bIOP and IOPcc after PRK was −2.3 to 8.5 mmHg. Notably, the bIOP values were higher for IOPs <20 mmHg and lower for IOPs >20 mmHg compared to 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 to the IOPcc, suggesting that the bIOP is a superior option for IOP reading following PRK.