Impact of intraocular lens material and design on light scatter: In vitro study

PURPOSE: To determine the typical in vitro straylight levels for intraocular lenses (IOLs) of different materials and designs. SETTING: Abbott Medical Optics, Inc., Groningen, the Netherlands. DESIGN: Experimental study. METHODS: Two optical bench setups were used to determine baseline straylight levels of IOLs placed in a saline-filled cuvette: one for forward scatter positions between 0.6 and 3.0 degrees and one for positions up to 22.0 degrees. Line-spread functions were measured using the small-angle setup, and scattered light intensity was measured using the wide-angle setup. From these measurements, the angular dependent straylight parameter was calculated. Ten IOLs of different materials (hydrophobic and hydrophilic) and designs (monofocal or diffractive multifocal and spheric or aspheric) were studied, and their measured straylight levels were compared with the levels in a 20-year-old and a 70-year-old healthy noncataractous human crystalline lens. RESULTS: Irrespective of the material or design, monofocal IOLs had straylight levels below or close to those of a 20-year-old human crystalline lens. Diffractive multifocal IOLs had straylight levels higher than those of monofocal IOLs but less than those of a 70-year-old human crystalline lens. With increasing angle, hydrophobic IOLs showed a gradual decrease in straylight level. After an initial decrease, hydrophilic IOLs showed an increase in straylight level for larger angles. CONCLUSIONS: The baseline straylight levels of IOLs were design and material dependent (hydrophobic < hydrophilic; monofocal < diffractive multifocal). Most monofocal IOLs had straylight levels below the levels in a 20-year-old human crystalline lens.