Dynamic intraocular pressure measurements during vitrectomy

Objectives: To directly measure dynamic intraocular pressure (IOP) during vitrectomy and to determine whether disposable pressure transducers placed in the infusion line can indirectly measure with accuracy the dynamic IOP during vitrectomy. Methods: Experimental clinical study of 10 patients undergoing vitrectomy. Dynamic IOP was sampled via an extra pars plana incision with a catheter transducer equipped to measure direct IOP during vitrectomy by attaching a metal flange near the pressure-sensing tip. Disposable blood pressure transducers were placed in the infusion tubing fluid path to determine the IOP by indirect means. During various maneuvers of vitrectomy including air-fluid exchange and gas-forced infusion, pressure measurements were taken simultaneously from the indwelling pressure transducer and the disposable blood pressure sensors in the infusion line. Results: The directly measured IOP varied between 0 and 120 mm Hg during vitrectomy. During fluid flow, the indirectly measured IOP, calculated from the infusion line pressures, accurately corresponded with the directly measured IOP. Conclusions: Closed vitrectomy causes wide fluctuations in IOP. The IOP can be accurately measured during fluid flow with inline sensors.