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Mohammadreza Razeghinejad, Lauren Maloley, Shane Jared Havens, Tara Rudebush, Vikas Gulati, Carol B Toris, Shan Fan, Deepta Abhay Ghate; Intraocular pressure measurement error after corneal procedures in a porcine enucleated eye. Invest. Ophthalmol. Vis. Sci. 2016;57(12):6455.
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© ARVO (1962-2015); The Authors (2016-present)
Intraocular pressure (IOP) measurement in eyes undergoing corneal refractive surgeries such as radial keratotomy and lamellar corneal surgeries may not be equal to the true IOP because of changes in corneal biomechanical properties. The purpose of this study is to investigate the validity of the IOP measurement in porcine eyes before and after corneal procedures.
The anterior chamber of fresh whole porcine eyes was cannulated using a 25 gauge needle attached via tubing to water columns set at specific fluid levels. The IOP in the intracameral compartment was thus maintained at 10, 20, 30 and 40 mmHg. A second 25 gauge needle connected via tubing to a pressure transducer was inserted into the anterior chamber to measure the manometric IOP(Tm) continuously. A pneumatonometer was used to measure IOP (Tp) at each set pressure level (10,20,30,40 mmHg) after allowing 10 minutes for pressure stabilization. IOP measurements at each level were repeated after one of the following corneal incisions was made: radial keratotomy (8 eyes), lamellar dissection (10 eyes), clear cornea standard phacoemulsification incisions (10 eyes). The readings of the Tm and Tp were compared before and after corneal procedures.
The Tp readings were lower than the Tm values at all IOP measurements before corneal procedures with increasing discrepancy as the Tm increased (p values <0.001). The mean±standard deviation of Tm and Tp at10, 20, 30, and 40 mmHg before the corneal procedure in 28 eyes were 11.9±0.3 mm Hg vs. 10.5±1.2 mm Hg, 21.5±0.3mm Hg vs.17.9±1.4mm Hg, 31.2± 0.6 mm Hg vs. 25.2±0.9mm Hg, and 41.2± 1.00mm Hg vs. 33.3±1.4mm Hg, respectively. The values for Tm and Tp at all IOP measurements before and after corneal procedures are shown in Table 1. Two way ANOVA test was performed with corneal procedures and Tm as the co-variates and the Tp error (Tm-Tp) as the outcome variable. There was no significant difference in the Tp error before and after all 3 corneal procedures.
Radial keratotomy, lamellar dissection and clear corneal incision did not affect Tp error in an enucleated porcine eye. The Tp error increased with increasing Tm.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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