Straylight from glistenings in intraocular lenses: In vitro study

PURPOSE: To assess light scattering from intraocular lenses (IOLs) with different numbers of laboratory-induced glistenings and create a model for predicting glistening effects on straylight.

SETTING: Rotterdam Ophthalmic Institute, Rotterdam, the Netherlands.

DESIGN: Experimental study.

METHODS: Glistenings were induced in 7 Acrysof IOLs using an accelerated aging method. To create different numbers of glistenings, the IOLs were immersed in a balanced salt solution at temperatures ranging from 37°C to 60°C and cooled to room temperature. The glistenings were analyzed with a microscope. Light scattering from the IOLs was assessed using a commercial straylight meter (C-Quant) adapted for in vitro evaluation of IOLs at a 2.5-degree and 7.0-degree scatter angle. A model was proposed relating straylight increase to the total number and surface portion (total number × area) of glistenings. Results were compared to the Mie theory.

RESULTS: The number of induced glistenings ranged from 114 to 12 386 per mm2, and the surface portion ranged from 1.4% to 26.9%. At 2.5 degrees, the range in the straylight parameter was 1.49 to 72.49 deg2/steradian (sr); at 7.0 degrees, it was 1.72 to 62.87 deg2/sr. Straylight was proportionally related to the total number of glistenings (0.0046 × total number) (R2 = 0.96) and the surface portion (217 × surface portion) (R2 = 0.97). The measurements agreed well with Mie theory.

CONCLUSIONS: Straylight from glistenings in IOLs had an accurate proportional association with their total number and surface portion. The proposed model proved effective in predicting straylight from glistenings. Numerous glistenings are needed to cause significant straylight elevation.