Phacoemulsification using an Active Fluidics System at Physiologic versus High IOP: Impact on Anterior and Posterior Segment Physiology

Purpose Evaluate the impact of high vs low intraoperative IOP during phacoemulsification on anterior and posterior physiology Setting Private practice in Des Moines, Iowa. Design Prospective, randomized, paired-eye clinical trial of patients anticipating bilateral cataract surgery. Methods Twenty-seven subjects randomized at the time of their first cataract surgery to either low intraocular pressure (IOP) or high IOP group. The subsequent cataract surgery was done under the alternate condition. During phacoemulsification and cortex removal, IOP was maintained either at low (≤28 mmHg) or at high (≥55-60 mmHg) levels. The primary outcome was fluid usage, with secondary outcomes of central corneal thickness, FAZ (foveal avascular zone) area, foveal and macular thickness, endothelial cell density and post-operative inflammation. Results Surgery with low IOP settings used less fluid (40.0cc v 55.6 cc, p<0.0001). Corneal thickness changes were smaller in low IOP eyes at 1 day and 1 week (3.0% v 8.1%, p=0.01; 3.1% v 4.4%, p=0.01) but were similar by 1 and 3 months. Endothelial cell density (ECD) dropped less in low IOP eyes at 1 and 3 months (-1.7%v-12.3%, p=0.001, 2.1% vs -8.9%, p=0.0003.) IOP remained a significant predictor of ECD change when relationship was controlled for fluid use and phaco energy. Retinal parameters did not vary among all eyes or when compared by IOP setting. Visual acuity was similar at all time points. Conclusions Low IOP settings resulted in less inflammation and less corneal trauma, as evidenced by a smaller drop in endothelial cell density and less postop corneal edema, when compared to high IOP settings. Retinal parameters did not change significantly. The different outcomes did not result in a difference in visual acuity.