Equilibrium water content and glistenings in acrylic intraocular lenses

Purpose: To investigate the possible relationship between temperature and water absorption in acrylic intraocular lenses (IOLs). Setting: Laboratory setting, Miyata Eye Clinic, Hiroshima, Japan. Methods: The equilibrium water content (amount of water absorbed per weight of the resin x 100) in 2 hydrophobic acrylic IOLs (AcrySof((R)) MA60BM [Alcon] and Sensar((R)) AR40 [AMO]) was calculated at 30degreesC, 40degreesC, and 50degreesC. The 2 IOLs were also subjected to 3 changes in temperature: from 37degreesC to 35degreesC, 39degreesC to 35degreesC, and 41degreesC to 35degreesC. They were incubated in physiological saline at the higher temperature for 2 hours and at the lower temperature for 30 days before being examined for glistening formation. Results: The water content was higher in the AR40 IOL than in the MA60BM IOL at all temperatures. A temperature-dependent increase in water content was seen in both IOLs, greater in the MA60BM. With a temperature change from 37degreesC to 35degreesC, glistening formation was not observed in either IOL. With a temperature change from 39degreesC to 35degreesC, glistenings were observed in the MA60BM IOL, and with a temperature change from 41degreesC to 35degreesC, they were observed in both IOLs. Conclusion: The change in the equilibrium water content caused by temperature changes between 30degreesC and 40degreesC is an important factor in glistening formation, and thus an IOL featuring less temperature-dependent water absorption is less likely to form glistenings. (C) 2004 ASCRS and ESCRS.