Etiology of surface light scattering on hydrophobic acrylic intraocular lenses

PurposeTo study the etiology of surface light scattering on hydrophobic acrylic intraocular lenses (IOLs).SettingAlcon Research Laboratories, Fort Worth, Texas, USA.DesignExperimental study.MethodsIntraocular lenses were obtained from clinical explantations (n = 5), from human cadavers (n = 8), and from finished-goods inventory (controls). Surface light scattering was measured and imaged with the IOLs in various hydration states (dry, short-term wetted, and long-term hydrated) before and after proteins were quantified and removed. Selected IOL samples were analyzed with x-ray photoelectron spectroscopy, scanning electron microscopy (SEM) with energy-dispersion x-ray analysis, Fourier-transform infrared spectroscopy with attenuated total reflectance, and cryogenic SEM with a focused ion beam.ResultsNo inorganic deposits or organic changes were observed on any IOL surface. Under clinically relevant hydrated conditions, surface light-scattering intensity was independent of proteinaceous biofilm state (P≥.11). Instead, the hydration state of the IOLs significantly contributed to the intensity of surface light scattering (P<.001); clinically explanted and cadaver-eye IOLs (but not control IOLs) exhibited minimal scatter when dry, intermediate scatter when wetted, and maximum scatter when hydrated. Subsurface nanoglistenings with diameters less than a micron and with locations up to 120 μm from the surface of the IOLs were characterized by SEM with a focused ion beam and were identified as the source of the hydration-related surface light scattering.ConclusionSurface light scattering on hydrophobic IOLs was predominantly caused by hydration-related subsurface nanoglistenings within the acrylic IOL material.Financial DisclosureThe authors are employees of Alcon Research, Ltd.