ABSTRACT
PURPOSE: To study the behavior of light rays that impact the frosted, double-square edge of an intraocular lens (IOL). SETTING: Optical Phisiophatological Department, University of Florence, Florence, Italy. METHODS: The interaction of light rays as a function of the edge design of a frosted, sharp-edged IOL was evaluated using an experimental eye model and an advanced ray-tracing program. The model simulates the irregularities of the frosted edge by the random overlap of sinusoidal phase gratings that have a random phase, an orientation, and a fixed period. RESULTS: The reduction in the maximum intensity of the ghost image by frosting the square edge was linked to the period of the microroughness. At a maximum microroughness, when the period is less than 5 microm, the reduction in the value of an unfrosted, square-edged IOL was 17.5%. CONCLUSIONS: The frosted edge had a small impact on reducing the intensity of the ghost image caused by the reflection of light from the double square edge of the IOL. Furthermore, in optics, the stray light from microroughness is generally considered to be a drawback because it can decrease contrast sensitivity.
Subject(s)
Lenses, Intraocular , Scattering, Radiation , Humans , Light , Models, Anatomic , Models, Theoretical , Prosthesis DesignABSTRACT
PURPOSE: To study the distribution and intensity of reflected glare images from 3 intraocular lens (IOL) edge designs. SETTING: Eye Institute, University of Florence, Florence, Italy. METHODS: The interaction of light rays as a function of edge design was evaluated using an experimental eye model and an advanced ray-tracing program. Three hydrophobic acrylic IOLs were studied: an acrylic square-edged (sharp) design, an acrylic round-edged design, and a new acrylic IOL with a rounded anterior edge and a sharp posterior edge. RESULTS: The rays hitting the sharp edge of an IOL caused peripheral arcs or circles of light on the side of the retina opposite the focused image. Edge reflections also occurred with the round-edged IOL, but the intensity of the reflected image was one tenth that of the intensity with the sharp-edged design. The new round-/sharp-edged design reduced the maximum intensity of the reflected image to one third the intensity of the sharp-edged reflected image. CONCLUSIONS: The experimental findings with an acrylic IOL that combines a sharp posterior edge with a low incidence of reflected edge glare are promising.
