Glistenings are fluid-filled microvacuoles that form within the intraocular lens (IOL) optic when the IOL is in an aqueous environment. They are observed in all types of IOLs but have been mainly associated with hydrophobic acrylic IOLs. Experimental and clinical studies suggest the various hydrophobic acrylic IOLs on the market exhibit different tendencies toward glistenings. Factors influencing glistening formation include IOL material composition, manufacturing technique, packaging, associated conditions such as glaucoma or those leading to breakdown of the blood-aqueous barrier, as well as concurrent use of ocular medications. Although the impact of glistenings on postoperative visual function and the evolution of glistenings in the late postoperative period remain controversial, IOL explantation has rarely been reported. The phenomenon of surface light scattering has also been described in association with hydrophobic acrylic IOLs. Its mechanism of formation is controversial but may be related to long-term phase separation water near the IOL surface, although not seen as microvacuoles. The author has no financial or proprietary interest in any material or method mentioned. Copyright 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.