Intraocular Pressure Control in Vitreoretinal Surgical Systems

A comparison was made between the Constellation^® Vision System with intraocular pressure (IOP) control and the Enhancing Visual Acuity (EVA) system with automatic infusion compensation (AIC) during a simulated vitrectomy in a closed eye model.

An acrylic eye model was connected to a vitrectomy probe, an infusion cannula, and a pressure transducer. The Constellation and EVA systems were tested using 25-gauge probes in vacuum mode with vacuum settings at 250, 450, and 650 mmHg. The target IOP was 30 mmHg. Average IOP was assessed before aspiration (initial IOP), during vitreous removal (vitreous IOP), and after vitreous removal and replacement with Alcon's BSS^® sterile irrigation solution (BSS IOP).

Using Constellation's IOP control, target IOP (30±2.5 mmHg) was maintained 93%, 74%, and 63% of the time at 250, 450, and 650 mmHg of vacuum, respectively. At 650 mmHg, initial IOP, vitreous IOP, and BSS IOP were 30.18±0.18, 30.99±0.66, and 31.55±1.38 mmHg. Using EVA with AIC, target IOP was maintained 16%, 17%, and 23% of the time at 250, 450, and 650 mmHg of vacuum. At 650 mmHg, initial IOP, vitreous IOP, and BSS IOPs were 30.54±0.08, 44.62±1.24, and 29.92±0.72 mmHg (P<0.0001).

When confronted with dynamic fluid conditions during vitreous removal, the Constellation system with IOP control automatically maintained stable IOP in the target range 63% to 93% of the time at different vacuum settings versus ≤23% of the time with the EVA system with AIC.