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 4 porcine eyes, and IOP fluctuations were evaluated. We performed 3-port vitrectomy using the Constellation® Vision or the EVA® Phaco-Vitrectomy system. Each 20-s experiment was conducted 5 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 was 15.9 ± 1.6 and 11.9 ± 1.4 mm Hg, respectively (p < 0.05), using the Constellation system; 23.2 ± 1.4 and 14.1 ± 0.7 mm Hg, respectively (p < 0.001), using the EVA vacuum mode; and 15.0 ± 0.5 and 11.5 ± 1.4 mm Hg, 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, 35.7 ± 0.9, and 6.4 ± 0.2 mm Hg, 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.