Design Of Achromatic Extended Depth-of-Focus IOL

Cataract has become the first blinding eye disease in the world,and surgical implantation of IOL is currently the most effective way to treat cataracts.At present,the most widely used clinical application is multifocal IOL,but it is prone to image overlap of different focus in use,resulting in certain impact on vision.The further developed extended depth-of-focus(EDOF)IOL can largely avoid multifocal loss of focus while achieving clear vision from far to near and continuous range.EDOF IOL also have disadvantages such as poor quality of near vision imaging and low light energy utilization.Taking the expansion of depth of focus as the main goal,this paper proposes a design method of achromatic EDOF intraocular lens based on folding and diffraction mixing,which improve the quality of closerange imaging through the sub-regional design of the diffraction surface linked to the pupil size,increase the utilization of light energy,and expand the field of view while eliminating chromatic aberration The main research contents are as follows:Firstly,on the basis of extensive investigation and analysis of the research status at home and abroad,the method of diffractive plane sub-region optimization is applied to the design of the artificial lens,from the central zone of the diffraction surface to the outward optimization of the surface type parameters of each region,until the largest area of the diffraction surface.The surface type of different regions uses all object distances and all fields of view for design optimization,and the pupil size is adjusted every new area of optimization,so that the light height of all fields of view does not exceed the radius of the current area.This method can improve the utilization rate of light energy,effectively expand the depth of focus and achromatic,improve the quality of close-up imaging,and minimize the influence of pupil enlargement on imaging.The specific design scheme is that the front surface of the IOL adopts a binary surface,divides its surface into multiple diffraction regions,and optimizes the surface shape of each diffraction area to achieve the functions of expanding depth of focus and achromatic difference.The posterior surface of the intraocular lens is optimized by even aspheric surface and Q-type aspheric surface,and the aspheric surface is used to eliminate the spherical aberration of the human cornea.Then,the diffraction surface corresponding to the 3mm pupil diameter is divided into two regions by this method,and two design schemes of achromatic EDOF IOL are obtained through surface design and optimization.The design results demonstrate that the use of diffractive surface sub-area optimization can achieve the function of extending the depth of focus while improving the light energy utilization.Then,the diffractive plane was then divided into nine regions using this method,and the face shape parameters of each region were optimized one by one from the center outward to obtain two design solutions for a nine-region achromatic extended depth-of-focus IOL at a pupil diameter of 5.9 mm.Finally,the design scheme of binary+Q-type aspheric lens is thinned by the fabrication principle of Fresnel lens,and the tolerance analysis of the design is carried out.The design results of achromatic EDOF IOL in nine regions show that both design schemes meet the requirements.In general,the design scheme of the Q-type aspheric surface on the back surface is better than that of the even aspheric surface.The human eye model embedded with this artificial lens has MTF values higher than 0.4 at a spatial frequency of 501p/mm under the conditions of pupil size of 3 mm,±8°field of view,object distance from 0.25 m to infinity,and complex color light(wavelengths selected from five bands of 470 nm,510 nm,555 nm,610 nm,and 670 nm).This design effectively extends the depth of focus and improves the quality of near imaging within 0.25～0.4m while maintaining the quality of far and mid-range imaging,the system’s vertical chromatic aberration is controlled within the Airy spot,and the field of view is expanded compared to other similar IOL.When the pupil changes from 2 mm to 5.5 mm,the MTF value(501p/mm)for all wavelengths and object distances in the central field of view is still higher than 0.2,effectively reducing the effect of pupil enlargement on imaging and improving the optical energy utilization of the system from the design method,achieving the desired goal.