* BACKGROUND AND OBJECTIVE: To compare the influence of low-molecular-weight viscoelastics on postoperative intraocular pressure (IOP) and corneal endothelial cell loss after phacoemulsification surgery. * PATIENTS AND METHODS: Sixty-nine eyes undergoing phacoemulsification surgery were randomized to have either Opegan (Santen Pharmaceuticals, Osaka, Japan) alone or the soft-shell technique using Viscoat (Alcon Surgical, Fort Worth, TX) during phacoemulsification. The IOP was measured preoperatively and at 5 and 24 hours postoperatively. Intraoperative factors and corneal endothelial cell loss were also examined. * RESULTS: Mean IOP was increased at 5 hours after surgery but returned to preoperative levels at 24 hours in the Opegan group, whereas it remained higher at 24 hours than at preoperative levels in the soft-shell group. When comparing groups, IOP at 5 and 24 hours postoperatively in the Opegan group was significantly less than that in the soft-shell group. Corneal endothelial cell loss was approximately the same in the two groups. * CONCLUSION: The increase in IOP following phacoemulsification surgery with the use of Opegan was less than that with the soft-shell technique using Viscoat, although endothelial injury was almost the same. [Ophthalmic Surg Lasers Imaging 2004;35:453-459.]