The impact of glistenings on the optical quality of a hydrophobic acrylic intraocular lens

Abstract

Purpose: To study the effect of glistenings on the optical quality of a hydrophobic acrylic intraocular lens (IOL).

Setting: David J. Apple Laboratory, Heidelberg, Germany.

Design: An in vitro laboratory study.

Methods: An accelerated aging protocol was used to induce glistenings (microvacuoles) in 38 hydrophobic acrylic IOLs. The IOLs were warmed to 45°C and then cooled to 37°C. Image analysis of light-microcopy photographs determined the number and size of microvacuoles (MV). A classification was applied based on the glistening number per mm²: grade 0 (none), grade 1 (1-100), grade 2 (101-200), grade 3 (201-500) and grade 4 (more than 500). An optical bench was used to measure each IOL's modulation transfer function (MTF) and Strehl ratio to evaluate the impact of glistenings on image quality.

Results: Glistenings were observed in all IOLs. The mean glistening numbers ± SD (MV/mm²) in grades 1 through 4 were 74 ± 12.7, 142 ± 22.2, 297 ± 76.2, and 1509 ± 311.9, respectively. The mean glistening sizes in grades 1 through 4 were 13.28 ± 3.85 μm, 15.88 ± 2.08 μm, 16.85 ± 3.23 μm, and 15.27 ± 2.25 μm, respectively. Statistical analysis showed that grades 1 through 3 did not change the optical quality; however, in grade 4, the MTF and the Strehl ratio were significantly affected.

Conclusion: A limited number of glistenings (<500 MV/mm²) had no effect on the image quality. Although statistically significant deteriorations in the MTF and the Strehl ratio were observed in grade 4, the effects found were small and are unlikely to affect the visual quality.