Abstract
Purpose: :
Foldable lens are becoming increasingly used for cataracts in pediatric and young adult patients. PMMA (polymethyl methacrylate) materials show little degradation when used in long–term usage, but long–term usage of foldable lens has not been sufficiently assessed. In the current study, we conducted accelerated degradation tests of various types of acrylic lens to assess the degradation status, light transparency and change in weight of intraocular lenses.
Methods: :
Intraocular lens studied: VA–60BB(AF–1),AR40e(Sensar),SA60AT(AcrySof1P)MA60BM(Acrysof 3P),N4–18B(Nex–Acri)
Samples were placed in a screw–cap test tube containing pure water and stored in a 100 degree oven for 58 days or 115 days to determine the accelerated degradation status, degree of light transparency, and weight change under the harsh accelerated conditions. Based on the Arrhenius formula for accelerated degradation of polymeric materials, 58 days were considered to correspond to 10 years, and 115 days to 30 years.
Results: :
Accelerated degradation status: In the harsh acceleration group, N4–18B and AR40e showed slight cloudiness and VA–60BB, SA60AT and MA60BM showed extensive cloudiness in the 58–day group. SA60AT, MA60BM and AR40e showed extensive yellow–white cloudiness in the 115–day group. Light transparency: AR40e, SA60AT and MA60BM showed a decrease of 50% or more. (115–day group)
Weight change: The dry weight changes were seen with SA60AT (–22.0%), AR40e (–9.0%), N4–18B (–5.0%), MA60BM (–4.8%) and VA–60BB (–2.8%). (115–day group)
Conclusions: :
Acrylic lens has a molecular structure that preserves softness, and it is thought that under harsh accelerated conditions, this molecular structure allows ready efflux of monomers, along with uptake of water molecules into the structure, resulting in the cloudiness. In particular, SA60AT showed extensive cloudiness and white–yellow cloudiness and greater extent of weight change. It is estimated that pediatric and young adult patients will have 70–80 years of active life after intraocular lens insertion. Selection of the intraocular lens for pediatric use from the viewpoint of lens degradation will require further consideration.
Keywords: intraocular lens • intraocular lens • intraocular lens