• Retina/Vitreous

    This experimental study conducted in porcine eyes found that the new Alcon Constellation Vision System can moderate IOP fluctuations during vitrectomy.

    This device is equipped with a pressure control system to maintain constant IOP independent of aspiration flow rates during vitrectomy. The intraoperative IOP fluctuations with this system, however, have not previously been assessed in detail.

    The authors used the system to perform 23- and 25-gauge vitrectomy in porcine eyes.

    Using the 23-gauge system with the IOP control setting turned on, IOP decreased from 30 to 23.7 mm Hg after starting vitreous cutting, and then returned to 30 mm Hg in 2.6 seconds. When the IOP control setting was turned off, IOP decreased to 19.1 mm Hg in 0.9 seconds, and remained at that pressure.

    Under aspiration at 650 mm Hg without cutting, IOP declined from 30 to 12.2 mm Hg and then returned to 30.6 mmHg in 2.6 seconds with the IOP control setting turned on. When the IOP control setting was turned off, IOP decreased to 2.2 mm Hg in 9.7 seconds and did not recover. When the sclera was compressed without aspiration, IOP rapidly increased to 70 to 100 mm Hg and then slowly decreased to 30 mm Hg in 3.5 to 4 seconds, with or without the IOP control system.

    The authors note that some of the intraoperative complications during closed eye surgery are associated with significant fluctuations in IOP. For example, expulsive choroidal hemorrhage, vitreous hemorrhage and choroidal detachment can occur after a sudden drop in IOP.

    They conclude that ‘‘gentle surgery’’ with relatively smaller IOP fluctuations would be preferred for vitrectomy. They also recommend conducting experiments on vitrectomy and IOP fluctuation in human eyes.