Equilibrium water content and glistenings in acrylic intraocular lenses

To investigate the possible relationship between temperature and water absorption in acrylic intraocular lenses (IOLs).

Laboratory setting, Miyata Eye Clinic, Hiroshima, Japan.

The equilibrium water content (amount of water absorbed per weight of the resin x 100) in 2 hydrophobic acrylic IOLs (AcrySof MA60BM [Alcon] and Sensar AR40 [AMO]) was calculated at 30 degrees C, 40 degrees C, and 50 degrees C. The 2 IOLs were also subjected to 3 changes in temperature: from 37 degrees C to 35 degrees C, 39 degrees C to 35 degrees C, and 41 degrees C to 35 degrees C. 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.

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 37 degrees C to 35 degrees C, glistening formation was not observed in either IOL. With a temperature change from 39 degrees C to 35 degrees C, glistenings were observed in the MA60BM IOL, and with a temperature change from 41 degrees C to 35 degrees C, they were observed in both IOLs.

The change in the equilibrium water content caused by temperature changes between 30 degrees C and 40 degrees C is an important factor in glistening formation, and thus an IOL featuring less temperature-dependent water absorption is less likely to form glistenings.