Change of the focused depth of biconvex Toric intraocular lens in Hwey-Lan Liou schematic eye

Abstract

Background Toric intraocular lens (IOL) has two optical powers in two perpendicular directions, and it could result in many different optic performance from spherical IOL. Objective This study was to evaluate the depths of focus of spherical, aspherical and Toric IOL under polychoromatic light by Hwey-Lan Liou schematic eye. Methods Hwey-Lan Liou schematic eye was created using Zemax software, and the alterations of focusing depth of Tecnis ZA9003 IOL (a spherical IOL), SN60AT IOL(a aspherical IOL), Arcysof Toric IOL were evaluated and compared based on Hwey-Lan Liou schematic eye by ray tracing method. Results The modulation transfer function (MTF) was perfect and the depth of defocus was equal under the zero defocus and under the pupil diameter of 3 mm with symmetrical focus curve in plus or minus two-axis in both spherical IOL and Toric IOL. The MTF decreasing with 5 mm pupil compared with that with 3 mm pupil. The MTF was declined under the pupil diameter of 5 mm compared with 3 mm in spherical IOL and Toric IOL along with the decrease of focus depth and the drifting of MTF toward negative axis. However, only the focus depth was decreased but MTF appeared to be stable in aspherical IOL. Conclusions Toric IOL and spherical IOL exhibit similar trends in focus depth change, and their focus depths decrease with the increase of pupil diameter. In addition, Toric IOL and spherical IOL show good light focus during minus defocus shifting. Key words: Lenses, intraocular; Astigmatism; Eye, artificial; Focused depth