We report the case of a 76-year-old Chinese man who had uneventful cataract phacoemulsification and hydrophilic acrylic intraocular lens (IOL) implantation 6 years previously. He presented with decreased vision; a homogeneous milky substance was found between the posterior chamber IOL and the posterior capsule without IOL displacement or a change in the refractive status. The milky substance was aspirated from the capsular bag. Biochemical analysis showed the concentrations of proteins and Ca(++) in the milky liquid were higher than those in the aqueous humor. Protein identification by mass spectrometry indicated that the milky liquid contained a high concentration of alpha-crystallin and beta-crystallin.