Abstract
Purpose: :
As a simple and convenient method of determining the stability of the IOL materials, we demonstrated that immersion of intraocular lenses (IOLs) in water at high temperature for an extended period leads to opacification and deterioration. Changes in opacity and the associated deterioration of resolution were compared after a severe accelerated deterioration test for periods equivalent to 5, 6, 7, 8, 15 and 20 years.
Methods: :
Three each of the following 5 types of colored acrylic IOLs were used: SN60WF (Alcon) and AN6K (KOWA), manufactured by the cast molding method, and NY-60(HOYA), NX-60 (Santen) and NS-60YG (NIDEK), manufactured by the lath-cut method. Each IOL was placed in a 50-mL screw-tube bottle containing ultrapure water, and soaked at 100°C for 29, 35, 40, 46, 86 and 115 days (corresponding to 5, 6, 7, 8, 15 and 20 years, respectively). The resolution and MTF (Modulated Transfer Function) of the IOLs were observed after 115 days.
Results: :
Appearance: Opacities, to a greater or less degree, were observed in all IOLs in water except NX60. When the IOLs were dried at a room temperature of 25°C for 48 hours, opacity disappeared from all IOLs except SN60WF.Resolution: The resolution of NY-60 declined after 5 years. No measurement was possible after 15 years in the case of SN60WF. AN6K remained clear for 8 years, but resolution declined after 15 years. NX-60 and NS-60YG showed no changes for 20 years. MTF: NX-60 and NS-60YG showed favorable values even after the 20-year-accelerated deterioration test.
Conclusions: :
Long-term observation of colored acrylic IOLs after a severe accelerated deterioration test suggested that they can be roughly grouped into those with reversible changes and those with irreversible changes. Furthermore, some IOLs showed no changes in either resolution or MTF.
Keywords: intraocular lens • clinical laboratory testing • refractive surgery: optical quality