Fig. 61. Proposed mechanism of optic swelling. Selective irradiation of the central zone of the IOL polymerizes the macromer creating a chemical potential between the irradiated and nonirradiated regions. To reestablish equilibrium excess macromer diffuses into the irradiated region causing swelling. Irradiation of the entire IOL “locks” the macromer and shape change. (Courtesy of Calhoun Vision, Pasadena, CA.)