Abstract
Purpose: :
The purpose of the study is to determine what typical stray light levels are for intraocular lenses (IOLs) with different designs and materials.
Methods: :
The stray light levels of IOLs made from 3 different materials (2 hydrophobic acrylics and 1 silicone) and 3 different designs (spherical monofocal, aspheric monofocal and diffractive multifocal) were compared. The IOLs were measured on an optical bench in and eye model that reproduces the spherical and chromatic aberration of an average pseudophakic eye. From five line spread functions (LSF), obtained by stepwise lateral displacement of the CCD camera, a light intensity vs. angle plot was constructed. This data was then used to calculate the accompanying angularly dependent stray light parameters for each IOL model for forward scatter positions between 0.6 and 2 degrees. These graphs for different designs and materials were compared with each other and to the levels published for a 20 and 70 year old human crystalline lens.
Results: :
The stray light levels of all monofocal lenses were below or comparable to the stray light levels measured for a 20 year old human crystalline lens. Hydrophobic acrylic monofocal aspheric lenses have lower stray light levels than monofocal spherical lenses. The stray light levels for monofocal lenses made from silicone were higher than stray light values for lenses from hydrophobic acrylics. Typical values for the stray light of aspheric monofocal lenses at 2 degrees vary from 1.0 to 2.6 while the stray light for a healthy 20 year old crystalline lens is 3.42. Acrylic diffractive multifocal stray light levels are between that of a 20 year old and a 70 year old healthy human crystalline lens.
Conclusions: :
IOLs made from hydrophobic acrylics have similar design-dependent stray light levels, with multifocal IOLs having the highest stray light levels followed by monofocal spherical IOLs. Monofocal aspheric IOLs have the lowest stray light levels. Silicone lenses have higher straylight levels than comparable hydrophobic acrylic lens designs. All lenses tested have stray light levels lower than that of a 70 year old healthy human crystalline lens for a forward scatter measured between 0.6 and 2 degrees.
Keywords: intraocular lens • optical properties