Ex Vivo Comparison of Intraocular Pressure Fluctuation During Pars Plana Vitrectomy Performed Using 25- and 27-Gauge Systems.

INTRODUCTION The purpose of this study was to compare intraoperative intraocular pressure fluctuation using different aspiration systems and 25- and 27-gauge vitreous surgery probes. METHODS Ex vivo, pars plana, 25- and 27-gauge vitreous surgery was performed on four porcine eyes, and IOP fluctuations were evaluated. We performed three-port vitrectomy using the Constellation® Vision or the EVA® Phaco-Vitrectomy system. Each 20-s experiment was conducted five times for each set of conditions, each with the same substituted balanced salt solution. Real-time intraoperative intraocular pressure measurement was performed at the distal end of the infusion tube. Intraocular pressure was measured during core vitrectomy; core vitrectomy with fluid aspiration; peripheral vitreous shaving with scleral indentation; and fluid-gas exchange. The Mann-Whitney U test was used to evaluate statistical significance. RESULTS Mean ± standard deviation intraoperative intraocular pressure fluctuation during 25- and 27-gauge core vitrectomy were 15.9 ± 1.6 mmHg and 11.9 ± 1.4 mmHg, respectively (P < 0.05), using the Constellation system; 23.2 ± 1.4 mmHg and 14.1 ± 0.7 mm Hg, respectively (P < 0.001), using the EVA vacuum mode; and 15.0 ± 0.5 mmHg and 11.5 ± 1.4 mmHg, respectively (P < 0.05), using the EVA flow mode. The smallest intraoperative intraocular pressure fluctuations during core vitrectomy with fluid aspiration, peripheral vitreous shaving with scleral indentation, and fluid-gas exchange, were all achieved using the 27-gauge EVA flow mode; these values were 14.2 ± 0.4 mmHg, 35.7 ± 0.9 mmHg, and 6.4 ± 0.2 mmHg, respectively. CONCLUSION Regardless of the aspiration system, intraoperative intraocular pressure fluctuation was lower during 27-gauge than during 25-gauge vitrectomy. The 27-gauge EVA flow mode produced optimal intraoperative intraocular pressure stability.