Influence of the intraocular lens optic–haptic junction on illumination of the peripheral retina and negative dysphotopsia

Abstract

PURPOSE: Use optical modeling to evaluate the effect of the intraocular lens (IOL) optic-haptic junction on retinal illumination and negative dysphotopsia. SETTING: Mayo Clinic, Rochester, Minnesota, USA. DESIGN: Schematic model eye. METHODS: Ray-tracing software for an extended light source was used to simulate retina illumination in a pseudophakic eye with a biconvex high-index acrylic IOL and a 2.5 mm pupil. The haptic junction was modeled using an annular cone of haptic material of 0.75 mm width located between the optic and haptic. Ray-tracing diagrams and simulated retina illumination profiles were compared with and without the haptic junction. Retinal locations were scaled to visual angles from 70 to 110 degrees horizontally. RESULTS: Light incident on the peripheral optic creates a nonuniform retina illumination pattern consisting of a 5-degree band of nonilluminated retina bounded posteriorly by light refracted by the optic and anteriorly by light that missed the optic. Light incident on the haptic junction illuminates retina differently in that light that typically misses the optic (input angle 79 to 91 degrees) is instead refracted at a large angle or internally reflected by the haptic junction, which removes the illuminated peripheral retina that would otherwise delineate the shadow region. Further modification to the haptic junction region improved peripheral retina illumination and shifted the shadow region 10 degrees anteriorly. CONCLUSIONS: The haptic junction illuminated the peripheral retina differently than the peripheral optic, and this might explain why a horizontal haptic junction minimizes negative dysphotopsia. A modification to the optic-haptic junction redirected illumination and shifted the retina shadow anteriorly, possibly decreasing awareness.